{392}FAM. 17. HIMANTOPTERIDAE (THYMARIDAE of some authorities) are placed

by Hampson in the sub-family Phaudinae of Zygaenidae characterised by the

absence of the mouth-parts. The Himantopteridae are small moths, and have

the scales on the wings very imperfect and hair-like; the hind wings form

long slender tails, so that the Insects scarcely look like moths. They are

peculiar to India and Africa. In the South African genus _Dianeura_

(belonging really to Phaudinae) also the wings are scaleless and nearly

transparent.

FAM. 18. HETEROGYNIDAE.—Consists of the single genus _Heterogynis_ which

has hitherto been found only in the south of Europe. This is an important

form connecting Zygaenidae and Psychidae. The larvae resemble those of

Zygaena, and construct an oval cocoon for their metamorphosis. The male

issues as a small moth of smoky colour, the scales being but imperfect; the

female chrysalis shows no trace of any appendages, and the imago is

practically a maggot, and never leaves the cocoon; in it she deposits her

eggs, and the young larvae hatch there.[275]

FAM. 19. PSYCHIDAE.—Small, or moderate-sized moths, with imperfect scales,

and little or no colour beyond certain shades of duskiness; the sexes very

different, the female being wingless and sometimes quite maggot-like; the

male often with remarkable, bipectinate antennae, the branches sometimes

very long and flexible. Larva inhabiting a case that it carries about. This

family consists of Insects unattractive in appearance but presenting some

points of great interest. It is frequently stated that the Psychidae are

destitute of scales, but Heylaerts states[276] that, in addition to hairs,

scales of a more or less imperfect formation are present in all, but that

they are, like those of some Sphingidae (_Macroglossa_), very easily

detached. There is much difference in the females, some having

well-developed legs, while others are not only apterous, but are bare and

destitute of appendages like a maggot, while in certain cases (Fig. 196,

G), the head is reduced in size and is of peculiar form so as to make the

Insect look really like the larva of one of the parasitic Diptera. These

females never leave their cases, but deposit their eggs {393}therein, and

inside, also, their former pupa-skin; and here the young hatch; the

peculiar little larvae are very numerous, and it is suggested that they

make a first meal on the body of their parent, but this we believe has not

been satisfactorily ascertained. Great differences as to the condition of

the legs, antennae, etc., are said to exist in species of the same genus.

There is also a remarkable diversity in the pupae of the females; the male

sex being normal in this respect. Some of the female pupae are destitute of

wing-sheaths and all other appendages, while others are said to possess

them, though there are no wings at all in the imago (_Fumea_, _e.g._).[277]

Great difficulties attend the study of these case-bearing Insects, and

several points require careful reconsideration, amongst them the one we

have just mentioned. The males fly rapidly in a wild manner, and may

sometimes be met with in swarms; their lives are believed to be very brief,

rarely exceeding a couple of days, and sometimes being limited to a few

hours.

[Illustration: Fig. 196—Metamorphosis of _Monda rhabdophora_. Ceylon. A,

Larva in case, nat. size; B, larva itself, magnified; C, case of female

during pupation; D, case of male during pupation; E, female pupa,

magnified; F, male moth, nat. size; G, female moth, magnified. (From

unpublished drawings by Mr. E. E. Green).]

The larvae are called basket-worms, and their baskets or cases are well

worthy of attention. Their variety is remarkable; the most extraordinary

are some of the genus _Apterona_ Fig. 197, B, which perfectly resemble the

shells of Molluscs such as snails; indeed, the specimens in the collection

at the British Museum were sent there as shells. This case is not, like

those of other Psychidae, constructed of earth or vegetable matter, but is

of silk and is in texture and appearance exactly {394}like the surface of a

shell. _Psyche helix_ is, according to Ingenitzky,[278] found in great

numbers near Lake Issyk-kul in Central Asia, where the larvae feed, in

their snail-shell-like cases, on a grass, just like snails. Only females

could be reared from these larvae. The case of _Chalia hockingi_ (Fig. 197,

C) consists of little pieces of wood cut to the proper lengths, and

spirally arranged, so as to form a construction that would be quite a

credit to our own species. In some of the Canephorinae we meet with long

cylindrical cases, like those of Caddis-worms, or of Tineid larvae.

[Illustration: Fig. 197—Baskets, or cases, of Psychidae. A, _Amicta

quadrangularis_; B, _Apterona_ (or _Cochlophora_) _valvata_; C, _Chalia

hockingi_.]

Riley has given an account of several points in the structure and natural

history of one of the North American basket- or bag-worms, _Thyridopteryx

ephemeraeformis_; one of his points being the manner in which the newly

hatched larva forms its case.[279] This question has also been discussed by

Packard.[280] The larvae when hatched in unnatural conditions will make use

of fragments of paper, cork, etc., for the case; the act of construction

takes one or two hours, and the larva does not eat till the case is

completed. It walks in a peculiar manner, the legs of the third pair being

moved forwards together, as if they were the prongs of a fork.

This family is already one of considerable extent, but its study, as

already remarked, is but little advanced. Some naturalists are inclined to

place it among the Tineidae, but it is connected with Zygaenidae by means

of Heterogynidae. Mr. Meyrick divides it, placing _Psyche_ and

_Sterrhopteryx_ (the forms representing, according to his ideas, the family

Psychidae in Britain) in the series Psychina which includes Zygaenidae. He

{395}removes the other British genera, _Fumea_, and _Epichnopteryx_, to

Tineidae near _Solenobia_ and _Taleporia_. The group Canephorinae, to which

the two genera in question belong, was long since separated from Psychidae

by Herrich-Schäffer, but this course was condemned by Heylaerts.

Parthenogenesis has been thought by some to occur in numerous species in

this family, but Heylaerts says that it is limited to _Apterona crenulella_

var. _helix_, and even of this species males are found in certain

localities.

FAM. 20. COSSIDAE (_Goat-Moths_, or _Carpenter-Worms_).—Moths of moderate,

or rather large size, without proboscis, frequently with a dense covering

of matted, imperfect scales; the pattern being vague. The larvae bore into

trees in which they often make large burrows, leaving holes from which sap

exudes. Our common Goat-moth is a good specimen of this family, which is a

very widely distributed one. The Australian genus _Ptilomacra_ has very

large, pectinated antennae in the male. The larvae of Cossidae are nearly

bare of clothing and are unadorned; they form a slight cocoon of silk mixed

with gnawed wood. The pupa of the Goat-moth is remarkable for the great

development of the rows of teeth on the dorsal aspects of the segments of

the abdomen, and for the absence of consolidation in this part, six of the

intersegmental incisions being free, and the ventral aspect almost

membranous. Very little is known as to other pupae of the family. It is

believed that the generations of these Insects are fewer than usual, the

growth of the larva occupying a period of two or three years. The larva of

_Zeuzera aesculi_ forms a temporary cocoon in which it passes a

winter-sleep, before again feeding in the spring.[281] It is a moot

question whether the Zeuzeridae should be separated from the Cossidae or

not. The group includes our Wood-leopard moth, which, like many other

Zeuzerids, is spotted in a very striking but inartistic manner. The

position the family Cossidae should occupy in an arrangement of the

Lepidoptera is a very difficult question. Some consider the Insects to be

allied to Tortricidae. The wing-nervuration of _Cossus_ is very peculiar

and complex, there being four or five cells on the front wing, and three on

the hind one. Meyrick places Zeuzeridae as a family of his series Psychina,

but separates Cossidae proper (he calls them Trypanidae) as a family of the

series Tortricina.

{396}FAM. 21. ARBELIDAE.—Closely allied to Cossidae, but without frenulum,

and with less complex wing-nervures. A small family believed to be similar

to Cossidae in the life-history. The tropical African Arbelidae are

considered by Karsch to be a distinct family, Hollandiidae.

FAM. 22. CHRYSOPOLOMIDAE.—This family has been established by Dr.

Aurivillius[282] for an African genus, allied in wing-nervuration to

Cossidae; the Insects are like Lasiocampidae.

FAM. 23. HEPIALIDAE (_Ghost-_ and _Swift-Moths_).—Moths of very diverse

size, some gigantic; wings not fitting together well at the bases; without

a frenulum; no proboscis; the scales imperfect; the nervures complex. The

Hepialidae are extremely isolated amongst the Lepidoptera; indeed, they

have really no allies; the conclusion that they are connected with the

Micropterygidae being certainly erroneous. Although but small in

numbers—only about 150 species being known—they exhibit a remarkable

variety in size and colour. Many are small obscure moths, while others are

of gigantic size—six or seven inches across the wings—and are amongst the

most remarkably coloured of existing Insects. The great _Charagia_ of

Australia, with colours of green and rose, bearing white spots, are

remarkable. The South African _Leto venus_ is of large size, and has an

astonishing supply of glittering metallic splashes on the wings, making a

barbaric but effective display. The South Australian _Zelotypia staceyi_,

of enormous size, is also a handsome moth; but the majority of species of

the family are adorned only in the feeblest manner.

Very little is known as to the larvae; they are either subterranean,

feeding on roots, or they live in the wood of trees and shrubs. They are

nearly bare, and are apparently the lowest type of Bombycid larva. At the

same time, it would appear there is considerable variety amongst them.

Packard says[283] the young larva of _Hepialus mustelinus_ has the

arrangement of setae that is normal in Tineidae. The larva of _H. humuli_

seems to be a very simple form, but _H. hectus_ shows a considerable amount

of divergence from it. They probably live for several years; the larva of

_H. argenteo-maculatus_ in North America lives for three years, at first

eating the roots of Alder and then entering the {397}stems. The pupae are

also peculiar. They are of unusually elongate, cylindrical form, with

comparatively feeble integument, but with a considerable development of

chitinous, elevated, toothed ridges, on the dorsal aspect, and a very

strong ridge of this kind on the ventral surface of the seventh segment;

the wing-sheaths are short; it is very difficult to distinguish the full

number of abdominal segments. These pupae are remarkably agile, and by

wriggling and kicking are able to move a considerable distance; it is said

that they can force themselves to the surface even when the superficial

soil is quite hard. We cannot consider this pupa naturally placed amongst

either the pupae obtectae or incompletae of Chapman.

[Illustration: Fig. 198—Pupa of _Hepialus lupulinus_. Britain. A, Ventral;

B, dorsal aspect.]

We have already remarked that little is known as to the life-histories. The

species are probably prolific, a female of _H. thule_ having been known to

deposit more than 2000 eggs. Of the Australian forms little more is

known[284] than that they live in the wood of trees and shrubs, and are

rapidly disappearing; we may fear that some are extinct without ever having

been discovered, and others, also unknown but still existing, may disappear

only too soon; the wasteful destruction of timber in Australia having been

deplorable.

The peculiar habits of the Hepialidae are not likely to bring the Insects

to the net of the ordinary collector, and we believe they never fly to

light, hence it is probable that we are acquainted with only a small

portion of the existing species; their distribution is very wide, but

Australia seems to be their metropolis, and in New Zealand twelve species

are known. The genera as at present accepted are remarkable for their wide

distribution. _Leto_ is said to occur in South Africa and in the {398}Fiji

Islands; but we must repeat that the study of these interesting Insects is

in a very primitive state, and our present knowledge of their distribution

may be somewhat misleading.

The habits of the European _Hepialus_ in courtship have been observed to a

considerable extent and are of great interest, an astonishing variety and a

profound distinction in the methods by which the sexes are brought together

having been revealed.

_H. humuli_, our Ghost-moth, is the most peculiar. Its habits were detected

by Dr. Chapman.[285] The male is an Insect of exceptional colour, being

white above, in consequence of a dense formation of imperfect scales; the

female is of the brownish tints usual in Swift-moths. In the month of June

the male selects a spot where he is conspicuous, and hovers persistently

there for a period of about twenty minutes in the twilight; his colour has

a silvery-white, glistening appearance, so that the Insect is really

conspicuous notwithstanding the advanced hour. Females may be detected

hovering in a somewhat similar manner, but are not conspicuous like the

male, their colour being obscure; while so hovering they are ovipositing,

dropping the eggs amongst the grass. Females that have not been fertilised

move very differently and dash about in an erratic manner till they see a

male; they apparently have no better means of informing the hovering male

of their presence than by buzzing near, or colliding with him. Immediately

this is done, the male abandons his hovering, and coupling occurs. There

can be little doubt that the colour of the male attracts the female; but

there is a variety, _hethlandica_, of the former sex coloured much like the

female, and in some localities varieties of this sort are very prevalent,

though in others the species is quite constant. This variation in the

colour of the males is very great in Shetland,[286] some being quite like

the females. In _H. hectus_ the two sexes are inconspicuously and similarly

coloured. The male hovers in the afternoon or evening in a protected spot,

and while doing so diffuses an agreeable odour—said by Barrett to be like

pine-apple—and this brings the female to him, much in the same manner as

the colour of _H. humuli_ brings its female. The hind legs of the male

{399}are swollen, being filled with glands for secreting the odorous

matter.[287] This structure has led to the suggestion of the generic name

_Phymatopus_ for the Insect. Turning to other species of the genus, we find

that the normal relative rôles of the sexes are exhibited, but with

considerable diversity in the species. In _H. lupulinus_ the males fly

about with rapidity, while the female sits on a stem and vibrates her

wings; she thus attracts the males, but they do not perceive her unless

happening to come within three or four feet, when they become aware of her

proximity, search for and find her. It is doubtful whether the attraction

is in this case the result of an odour; it would appear more probable that

it may be sound, or that the vibration of the wings may be felt by the

male.

In _H. sylvinus_, _H. velleda_ and _H. pyrenaicus_ less abnormal modes of

attracting the males occur, the individuals of this latter sex assembling

in great numbers at a spot where there is a female. In the first of the

three species mentioned the female sits in the twilight on the stem of some

plant and vibrates the wings with rapidity; she does not fly; indeed,

according to Mr. Robson, she does not till after fertilisation move from

the spot where she emerged. In _H. pyrenaicus_ the female is quite

apterous, but is very attractive to the males, which as we have said,

assemble in large numbers near her. Thus within the limits of these few

allied forms we find radically different relations of the sexes.

1. The male attracts the female—(A) by sight (_H. humuli_); (B) by odour

(_H. hectus_).

2. The female attracts the male—(A) by vibration of wings (_H. lupulinus_

and _H. sylvinus_); (B) without vibration, but by some means acting at a

distance (_H. velleda_, _H. pyrenaicus_).

Little or nothing is known as to the habits of the great majority of the

more remarkable forms of the family. The gigantic Australian forms are

believed to be scarcely ever seen on the wing.

The Hepialidae differ from other Lepidoptera by very important anatomical

characters. The absence of most of the {400}mouth-parts is a character

common to them and several other divisions of Lepidoptera; but the labial

palpi are peculiarly formed in this family, being short and the greater

portion of their length consisting of an undivided base, which probably

represents some part of the labium that is membranous in normal

Lepidoptera. The thoracic segments are remarkably simple, the three

differing less from one another than usual, and both meso- and meta-notum

being much less infolded and co-ordinated. The wings are remarkable for the

similarity of the nervuration of the front and hind wings, and by the cell

being divided by longitudinal nervules so as to form three or four cells.

On the inner margin of the front wing there is near the base an incision

marking off a small prominent lobe, the jugum of Prof. Comstock. Brandt

mentions the following anatomical peculiarities,[288] viz. the anterior

part of the alimentary canal is comparatively simple; the respiratory

system is in some points like that of the larva; the heart is composed of

eight chambers; the appendicular glands of the female genitalia are

wanting. The testes remain separate organs throughout life. The chain of

nerve ganglia consists of the supra- and infra-oesophageal, three thoracic,

and five abdominal, ganglia, while other Lepidoptera have four abdominal.

FAM. 24. CALLIDULIDAE.—A small family of light-bodied diurnal moths having

a great resemblance to butterflies. In some the frenulum is present in a

very rudimentary condition, and in others it is apparently absent.

_Cleosiris_ and _Pterodecta_ are very like butterflies of the Lycaenid

genus _Thecla_. Although fifty species and seven or eight genera are known,

we are quite ignorant of the metamorphoses. Most of the species are found

in the islands of the Malay Archipelago, but there are a few in East India.

FAM. 25. DREPANIDAE (or DREPANULIDAE). (_Hook-tips_).—The larger moths of

this family are of moderate size; many of the species have the apex of the

front wing pointed or even hooked; some have very much the appearance of

Geometrid moths; they resemble very different members of that family.

_Oreta hyalodisca_ is remarkable on account of the very large, transparent

patch on each front wing, though the other species of the genus have

nothing of the sort. In the genus _Deroca_ we {401}find Insects with the

scales imperfect, they being few and small and approximating in form to

hairs; in _D. hyalina_ scales are nearly entirely absent. In other genera,

_e.g._ _Peridrepana_, _Streptoperas_, there is only a very inferior state

of scale-formation. The few larvae that are known are peculiar; they are

nearly bare of hair, without the pair of terminal claspers, while the body

is terminated by a long tubular process. They form a slight cocoon among

leaves.

The members of the family were formerly much misunderstood, and were

assigned to various positions in the Order. There are now about 30 genera,

and 150 species known, the geographical distribution of the family being

very wide. In Britain we have half a dozen species. _Cilix glaucata_

(better known as _C. spinula_) is said "to undoubtedly imitate" the

excrement of birds. No doubt the Insect resembles that substance so as to

be readily mistaken for it. This Insect has a very wide distribution in

North America, Europe and East India, and is said to vary so much in the

structure of its organs as to justify us in saying that the one species

belongs to two or three genera.

[Illustration: Fig. 199—Mature larva of _Apoda testudo_, on beech-leaf.

Britain.]

FAM. 26. LIMACODIDAE (or EUCLEIDAE).—These are somewhat small moths, of

stout formation, sometimes very short in the body, and with rather small

wing-area. The family includes however at present many Insects of diverse

appearance; there are numerous forms in which apple-green is a prominent

colour; some bear a certain resemblance to the Swifts, others to Noctuids;

some, _Rosema_ and _Staetherinia_, are of extraordinary shapes; certain

very small forms, _Gavara_, _Ceratonema_, resemble Tortricids or Tineids; a

few even remind one of Insects of other Orders; so that the group is a

mimetic one. _Nagoda nigricans_ (Ceylon) has the male somewhat like a

Psychid, while the female has a different system of coloration and

wing-form. In _Scopelodes_ the palpi are in both sexes remarkable;

elongated, stiff, directed upwards and brush-like at the tip. Altogether

there are about 100 genera and 400 species known; the distribution of the

family is very wide {402}in both hemispheres, but these Insects do not

occur in insular faunas. In Britain we have two genera, _Heterogenea_ and

_Apoda_ (better known as _Limacodes_[289]), each with a single species.

[Illustration: Fig. 200—Larva of _Apoda testudo_ just hatched. A, Dorsal

view of larva; B, C, D, a spine in different states of evagination. All

magnified. (After Chapman.)]

The early stages of these Insects are of great interest. The eggs, so far

as known, are peculiar flat oval scales, of irregular outline and

transparent; we have figured an example in Vol. V. Fig. 83. The eggs of the

same moth are said to vary much in size, though the larvae that emerge from

them differ little from one another in this respect. The latter are

peculiar, inasmuch as they have no abdominal feet, and the thoracic legs

are but small; hence the caterpillars move in an imperceptible gliding

manner that has suggested for some of them the name of slug-worms. The

metamorphoses of a few are known. They may be arranged in two groups; one

in which the larva is spinose or armed with a series of projections and

appendages persisting throughout life; while in the members of the second

group the spines have only a temporary existence. At the moment the young

larva of _Apoda testudo_ emerges from the egg it has no conspicuous spines

or processes, and is an extremely soft, colourless creature,[290] but it

almost immediately displays a remarkable system of complex spines. These

really exist in the larva when it is hatched, and are thrust out from pits,

as explained by Dr. Chapman. In the succeeding stages, the spines become

modified in form, and the colour of the body and the nature of {403}the

integument are much changed, so that in the adult larva (Fig. 199) the

spines have subsided into the condition of mere prominences, different in

colour from the rest of the surface. These larvae appear to be destitute of

a head, but there really exists a large one which is retracted, except

during feeding, into the body; the five pairs of abdominal feet of the

larvae of allied families are replaced by sucker-like structures on the

first eight abdominal segments. The spinneret of the mouth is not a pointed

tubular organ, but is fish-tailed in shape, and hence disposes the silky

matter, that aids the larva in moving on the leaves, in the form of a

ribbon instead of that of a thread. It has been stated that these peculiar

larvae "imitate" the coloured galls frequently found on the leaves of

trees. The North American forms of this family have very varied and most

extraordinary larvae.[291] In the pretty and conspicuous larva of _Empretia

stimulea_, the tubercles or processes of the body are, in the later stages,

armed with hairs, that contain a poisonous or irritating fluid, said to be

secreted by glands at the bases of the processes. These hairs are readily

detached and enter the skin of persons handling the caterpillars. The larva

of the North American Hag-moth, _Phobetron pithecium_, is a curious object,

bearing long, fleshy appendages covered with down. Hubbard makes the

following statement as to the instincts of this larva:[292]—"The hag-moth

larvae do not seek to hide away their cocoons, but attach them to leaves

and twigs fully exposed to view, with, however, such artful management as

to surroundings and harmonising colours that they are of all the group the

most difficult to discover. A device to which this Insect frequently

resorts exhibits the extreme of instinctive sagacity. If the caterpillar

cannot find at hand a suitable place in which to weave its cocoon, it

frequently makes for itself more satisfactory surroundings by killing the

leaves, upon which, after they have become dry and brown in colour, it

places its cocoon. Several of these caterpillars unite together, and

selecting a long and vigorous immature shoot or leader of the orange tree,

they kill it by cutting into its base until it wilts and bends over. The

leaves of a young shoot in drying turn a light tan-color, which

{404}harmonises most perfectly with the hairy locks of the caterpillar

covering the cocoon. The latter is, consequently, not easily detected, even

when placed upon the exposed and upturned surface of the leaf."

The cocoons of Limacodidae are unusually elaborate, the larva forming a

perfect lid in order to permit itself to escape when a moth. Chapman states

that the larva lies unchanged in the cocoon all winter, moulting to a pupa

in the spring, and that the pupa escapes from the cocoon previous to the

emergence of the moth.[293] Both Chapman and Packard look on the family as

really nearer to Microlepidoptera than to Bombyces; Meyrick (calling it

Heterogeneidae) places it at the end of his series Psychina next

Zygaenidae.

We may allude here to the little moths, described by Westwood under the

name of _Epipyrops_,[294] that have the extraordinary habit of living on

the bodies of live Homopterous Insects of the family Fulgoridae in India.

What their nutriment may be is not known. The larva exudes a white

flocculent matter, which becomes a considerable mass, in the midst of which

the caterpillar changes to a pupa. Westwood placed the Insect in Arctiidae;

Sir George Hampson suggests it may be a Limacodid, and this appears

probable.

FAM. 27. MEGALOPYGIDAE (or LAGOIDAE).—The American genera, _Megalopyge_ and

_Lagoa_, are treated by Berg and by Packard[295] as a distinct family

intermediate between Saturniidae and Limacodidae. The larva is said by the

latter authority to have seven pairs of abdominal feet instead of five

pairs—the usual number in Lepidoptera. When young the caterpillars of

_Lagoa opercularis_ are white and resemble a flock of cotton wool. When

full grown the larva presents the singular appearance of a lock of hair,

moving in a gliding, slug-like manner. Under the long silky hair there are

short, stiff, poison-hairs. The larva forms a cocoon, fitted with a hinged

trap-door for the escape of the future moth. This curious larva is

destroyed by both Dipterous and Hymenopterous parasites.

FAM. 28. THYRIDIDAE.—A small family of Pyraloid moths, exhibiting

considerable variety of form and colour, frequently with hyaline patches on

the wings. They are mostly small {405}Insects, and contain no very striking

forms. Some of them look like Geometrids of various groups. The family is

widely distributed in the tropical zone, and includes 25 genera, of which

_Rhodoneura_, with upwards of 100 species, is the chief one. The larvae are

said to be similar to those of Pyralidae. This family is considered by

Hampson and Meyrick to be ancestral to butterflies.[296]

[Illustration: Fig. 201.—Lappet-moth, _Gastropacha quercifolia_, ♀.

Britain.]

FAM. 29. LASIOCAMPIDAE (_Eggers_, _Lappet-moths_). Usually large Insects

densely covered with scales, without frenulum, but with the costal area of

the hind wing largely developed, and the male antennae beautifully

pectinate, Lasiocampids are easily recognised. They are well known in

Britain, though we have but few species. The flight of some of the species

is powerful, but ill-directed, and the males especially, dash about as if

their flight were quite undirected; as indeed it probably is. The

difference in the flight of the two sexes is great in some species. In the

genus _Suana_ and its allies we meet with moths in which the difference in

size of the two sexes is extreme; the males may be but 1½ inches across the

wings, while the very heavy females may have three times as great an

expanse. Kirby separates these Insects to form the family Pinaridae; it

includes the Madagascar silkworm, _Borocera madagascariensis_. The African

genus _Hilbrides_ is remarkable for the wings being destitute of scales,

and consequently transparent, and for being of very slender form like a

butterfly. The eggs of Lasiocampidae are smooth, in certain cases spotted

in an irregular manner like birds' eggs. Sometimes the parent covers them

with hair. The larvae are clothed with a soft, woolly hair, as well as with

a shorter and stiffer kind, neither beautifully arranged nor highly

coloured, and thus differing from the caterpillars of Lymantriidae; this

hair in some cases has very irritating properties. Cocoons of a close and

compact nature are formed, and hairs from the body are frequently mixed

with the cocoon. In {406}some species the walls of the cocoons have a firm

appearance, looking very like egg-shell—a fact which is supposed to have

given rise to the name of Eggers. Professors Poulton and Meldola have

informed us that this appearance is produced by spreading calcium oxalate

on a slight framework of silk, the substance in question being a product of

the Malpighian tubes.[297] In various families of Lepidoptera it happens

that occasionally the pupa exists longer than usual before the appearance

of the perfect Insect, and in certain members of this family—notoriously in

_Poecilocampa populi_, the December moth—this interval may be prolonged for

several years. There is not at present any explanation of this fact. It may

be of interest to mention the following case:—From a batch of about 100

eggs deposited by one moth, in the year 1891 (the Puss-Moth of the family

Notodontidae), some sixty or seventy cocoons were obtained, the feeding up

of all the larvae having been effected within fourteen days of one another;

fourteen of the Insects emerged as moths in 1892; about the same number in

1893; in 1894, twenty-five; and in 1895, eleven emerged. Lasiocampidae is a

large family, consisting of some 100 genera and 500 or more species, and is

widely distributed. It is unfortunately styled Bombycidae by some

naturalists.

FAM. 30. ENDROMIDAE.—The "Kentish glory," _Endromis versicolor_, forms this

family; it is a large and strong moth, and flies wildly in the daytime in

birch-woods. The larva has but few hairs, and is said when young to assume

a peculiar position, similar to that of saw-fly larvae, by bending the head

and thorax backwards over the rest of the body.

FAM. 31. PTEROTHYSANIDAE.—Consists of the curious East Indian genus

_Pterothysanus_, in which the inner margins of the hind wings are fringed

with long hairs. They are moths of slender build, with large wing-expanse,

black and white in colour, like Geometrids. There is no frenulum.

Metamorphoses unknown.

FAM. 32. LYMANTRIIDAE.—(Better known as LIPARIDAE). These are mostly small

or moderate-sized moths, without brilliant colours; white, black, grey and

brown being predominant; with highly-developed, pectinated antennae in the

male. The larva is very hairy, and usually bears tufts or brushes of

shorter hairs, {407}together with others much longer and softer, these

being sometimes also amalgamated to form pencils; the coloration of these

larvae is in many cases very conspicuous, the tufts and pencils being of

vivid and strongly contrasted colours. Some of these hairy larvae are

poisonous. A cocoon, in which much hair is mixed, is formed. The pupae are

remarkable, inasmuch as they too are frequently hairy, a very unusual

condition in Lepidoptera. The Lymantriidae is one of the largest families

of the old group Bombyces; it includes some 180 genera and 800 species, and

is largely represented in Australia. _Dasychira rossii_ is found in the

Arctic regions. In Britain we have eight genera represented by eleven

species; the Gold-tails, Brown-tails and Vapourer-moths being our commonest

Bombyces, and the latter being specially fond of the London squares and

gardens, where its beautiful larva may be observed on the leaves of roses.

Most of the Lymantriidae are nocturnal, but the male Vapourer-moth flies in

the daytime. In this family there are various species whose females have

the wings small and unfit for flight, the Insects being very sluggish, and

their bodies very heavy. This is the state of the female of the

Vapourer-moth. The males in these cases are generally remarkably active,

and very rapid on the wing.

Some of these moths increase in numbers to an enormous extent, and commit

great ravages. _Psilura monacha_—the Nun, "die Nonne" of the

Germans,[298]—is one of the principal troubles of the conservators of

forests in Germany, and great sums of money are expended in combating it;

all sorts of means for repressing it, including its infection by fungi,

have been tried in vain. The caterpillars are, however, very subject to a

fungoid disease, communicated by natural means. It is believed, too, that

its continuance in any locality is checked after a time by a change in the

ratio of the two sexes. It is not a prolific moth, for it lays only about

100 eggs, but it has been shown that after making allowance for the

numerous individuals destroyed by various enemies, the produce of one moth

amounts in five generations to between four and five million individuals.

The larva feeds on Coniferae, and on many leafy trees and shrubs. The young

{408}larva is provided with two sets of setae, one set consisting of very

long hairs, the other of setae radiating from warts; each one of this

second set of spines has a small bladder in the middle, and it has been

suggested that these assist in the dissemination of the young caterpillars

by atmospheric means.[299] These aerostatic setae exist only in the young

larva. The markings of the moth are very variable; melanism is very common

both in the larva and imago; it has been shown conclusively that these

variations are not connected, as black larvae do not give a larger

proportion of black moths than light-coloured caterpillars do. In England

this moth is never injurious. A closely allied form, _Ocneria dispar_, was

introduced by an accident into North America from Europe about thirty years

ago; for twenty years after its introduction it did no harm, and attracted

but little attention; it has, however, now increased so much in certain

districts that large sums of money have been expended in attempting its

extirpation.

_Dasychira pudibunda_ has occasionally increased locally to an enormous

extent, but in the limited forests of Alsace the evil was cured by the fact

that the caterpillars, having eaten up all the foliage, then died of

starvation.[300] _Teara melanosticta_ is said to produce columns of

processionary caterpillars in Australia.

FAM. 33. HYPSIDAE (or AGANAIDAE).—A family of comparatively small extent,

confined to the tropical and sub-tropical regions of the Eastern

hemisphere. The colours are frequently buff and grey, with white streaks on

the outer parts of the wings. We have nothing very like them in the

European fauna, our species of _Spilosoma_ are perhaps the nearest

approach. In _Euplocia_ the male has a pouch that can be unfolded in front

of the costa at the base of the anterior wing; it is filled with very long,

peculiar, hair-like scales growing from the costal margin; both sexes have

on each side of the second abdominal segment a small, projecting structure

that may be a sense-organ. The female is more gaily coloured than the male.

FAM. 34. ARCTIIDAE.—With the addition recently made to it of the formerly

separate family Lithosiidae, Arctiidae has become the most extensive family

of the old Bombycid series of moths, comprising something like 500 genera

and 3000 species. Hampson recognises four sub-families—Arctiinae,

Lithosiinae, {409}Nolinae, Nycteolinae,—to which may be added others from

America—Pericopinae, Dioptinae, Ctenuchinae; these sub-families being

treated as families by various authors. The sub-family Arctiinae includes

our Tiger- and Ermine-moths, and a great many exotic forms of very diverse

colours and patterns; the species of this division are, on the whole,

probably more variable in colour and markings than in any other group of

Lepidoptera. There are many cases of great difference of the sexes; in the

South American genus _Ambryllis_ the male is remarkable for its hyaline

wings with a few spots; while the female is densely scaled, and very

variegate in colour. There are some cases (the South European genus

_Ocnogyna_) where the female is wingless and moves but little, while the

male flies with great rapidity. _Epicausis smithi_, from Madagascar, one of

the most remarkable of moths, is placed in this division of Arctiidae; it

is of a tawny colour, variegate with black; the abdomen of this latter

colour is terminated by a large tuft of long scarlet hairs; the Insect has

somewhat the appearance of a Hummingbird-hawkmoth. _Ecpantheria_ is an

extensive genus of tropical American moths (having one or two species in

North America), of black and white or grey colours, with very complex

markings; the male in some species has a part of the hind wing produced as

a tail, or lobe, of a different colour.

The sub-family Pericopinae are almost peculiar to South America (two

species of _Gnophaela_ exist in North America); some of this sub-family

bear a great resemblance to Heliconiid butterflies.

The Dioptinae are likewise American moths of diurnal habits, and many of

them bear a striking resemblance to the Ithomiid butterflies they associate

with when alive.

The sub-family Lithosiinae is of great extent; our native "Footmen" give a

very good idea of it; the moths are generally of light structure, with

long, narrow front wings; a simple system of yellow and black colour is of

frequent occurrence. Many of this group feed in the larval state on

lichens. Hampson includes in this group the Nyctemeridae—light-bodied

diurnal moths, almost exclusively of black and white colours, of Geometrid

form, frequently treated as a distinct family.

The sub-family Nolinae is a small group of rather insignificant Insects, in

appearance like Pyralids or Geometrids; four or five {410}species are

native in Britain. Packard maintains the family Nolidae as distinct.[301]

The sub-family Nycteolinae consists of a few small moths the position of

which has always been uncertain; _Nycteola_ (better known as

_Sarrothripus_), _Halias_, and _Earias_ are all British genera that have

been placed amongst Tortrices, to which they bear a considerable

resemblance. _Sarrothripus_ is at present placed by Hampson in Noctuidae,

by others in Lithosiidae, by Meyrick in Arctiidae. The sub-family forms the

family Cymbidae of Kirby;[302] it includes at present only about 70

species, all belonging to the Eastern hemisphere. Two types of larvae are

known in it: one bare, living exposed on leaves; the other, _Earias_,

hairy, living among rolled-up leaves. _Halias prasinana_ is known from the

testimony of numerous auditors to produce a sound when on the wing, but the

_modus operandi_ has not been satisfactorily ascertained. Sound-production

seems to be of more frequent occurrence in Arctiidae than it is in any

other family of Lepidoptera; _Dionychopus niveus_ produces a sound by, it

is believed, friction of the wings. In the case of the genera _Setina_ and

_Chelonia_ the process is said to be peculiar to the male sex: Laboulbène

believes it to proceed from drum-like vesicles situate one on each side of

the base of the metathorax.[303]

FAM. 35. AGARISTIDAE.—An interesting assemblage of moths, many of them

diurnal and of vivid colours, others crepuscular. There is considerable

variety of appearance in the family, although it is but a small one, and

many of its members remind one of other and widely separated families of

Lepidoptera. The style and colour of the Japanese _Eusemia villicoides_ are

remarkably like our _Arctia villica_. In some forms the antennae are

somewhat thickened towards the tip and hooked, like those of the Skipper

butterflies. The family consists at present of about 250 species, but we

doubt its being a sufficiently natural one. It is very widely distributed,

with the exception that it is quite absent from Europe and the

neighbourhood of the Mediterranean Sea. In North America it is well

represented. The larvae, so far as known, are not very remarkable; they

have some lateral tufts of hair, as well as longer hairs scattered over the

body.

{411}The male of the Indian _Aegocera tripartita_ has been noticed to

produce a clicking sound when flying, and Sir G. Hampson has shown[304]

that there is a peculiar structure on the anterior wing; he considers that

this is rubbed against some spines on the front feet, and that the sound is

produced by the friction. Though this structure is wanting in the

acknowledged congeners of _A. tripartita_, yet it occurs in a very similar

form in the genus _Hecatesia_, already noticed under Castniidae.

FAM. 36. GEOMETRIDAE (_Carpets_, _Pugs_, _etc._)—This very extensive family

consists of fragile moths, only a small number being moderately stout

forms; they have a large wing-area; the antennae are frequently highly

developed in the males, but on this point there is much diversity. Either

the frenulum or the proboscis is absent in a few cases. The caterpillars

are elongate and slender, with only one pair of abdominal feet—placed on

the ninth segment—in addition to the anal pair, or claspers. They progress

by moving these two pairs of feet up to the thoracic legs, so that the body

is thrown into a large loop, and they are hence called Loopers or

Geometers. The family is universally distributed, and occurs even in remote

islands and high latitudes; in Britain we have about 270 species. The

family was formerly considered to be closely connected with Noctuidae, but

at present the opinion that it has more intimate relations with the

families we have previously considered is prevalent. Packard considers it

near to Lithosiidae, while Meyrick merely places the six families, of which

he treats it as composed, in his series Notodontina. Hampson adopts

Meyrick's six families as subfamilies, but gives them different names,

being in this respect more conservative than Meyrick, whose recent revision

of the European forms resulted in drastic changes in nomenclature.[305]

This classification is based almost exclusively on wing-nervuration. The

number of larval legs and the consequent mode of walking is one of the most

constant characters of the group; the few exceptions that have been

detected are therefore of interest. _Anisopteryx aescularia_ has a pair of

undeveloped feet on the eighth segment, and, according to Meyrick, its

allies "sometimes show rudiments of the other two pairs." The larva of

_Himera {412}pennaria_ is said to have in early life a pair of imperfect

feet on the eighth segment, which disappear as the larva approaches

maturity.

[Illustration: Fig. 202—Larva of _Amphidasis betularia_, reposing on a

rose-twig. × 1. Cambridge.]

The position of the abdominal feet and claspers throws the holding power of

the larva to the posterior part of the body, instead of to the middle, as

in other caterpillars. This, combined with the elongate form, causes these

larvae when reposing to assume attitudes more or less different from those

of other larvae; holding on by the claspers, some of these Insects allow

all the anterior parts of the body to project in a twig-like manner. The

front parts are not, however, really free in such cases, but are supported

by a thread of silk extending from the mouth to some point near-by. Another

plan adopted is to prop the front part of the body against a twig placed at

right angles to the supporting leaf, so that the caterpillar is in a

diagonal line between the two (Fig. 202). Other Geometers assume peculiar

coiled or spiral attitudes during a whole or a portion of their lives; some

doing this on a supporting object—leaf or twig—while others hang down

(_Ephyra pendularia_). Certain of the larvae of Geometridae vary in colour,

from shades of brown to green; there is much diversity in this variation.

In some species it is simple variation; in others it is dimorphism, _i.e._

the larvae are either brown or green. In other cases the larvae are at

first variable, subsequently dimorphic. In _Amphidasis betularia_ it would

appear that when the larva is hatched the dimorphism is potential, and that

the future colour, whether {413}green or brown, is settled by some

determining condition during the first period of larval life and cannot be

subsequently modified.[306] According to Poulton, the dark tint is due in

_A. betularia_ to colouring matter in the skin or immediately below it, and

the green tint to a layer of fat between the hypodermis and the superficial

muscles; this layer being always green, but more brightly green in the

larvae that are of this colour externally. Much discussion has occurred

about these larval attitudes and colours, and it seems probable that

Professor Poulton has overrated the value of protection from birds, mammals

and entomologists; the chief destroying agents being other than these, and

not liable to be thus deceived, even if the vertebrates are. In some cases

such resemblance as undoubtedly exists is not made the best use of. The

larva shown in figure 202 bore a wonderful resemblance, when examined, to

the rose-twigs it lived on, but the effect of this as a concealing agent

was entirely destroyed by the attitude; for this, being on different lines

to those of the plant, attracted the eye at once. This larva, and we may

add numerous other larvae, could have been perfectly concealed by adopting

a different attitude, but never did so; the position represented being

constantly maintained except while feeding.

In some species of this family the adult females are without wings, or have

them so small that they can be of no use for flight. This curious condition

occurs in various and widely-separated groups of the Geometridae; and it

would be naturally supposed to have a great effect on the economy of the

species exhibiting it, but this is not the case. Some of the flightless

females affect the highest trees and, it is believed, ascend to their very

summits to oviposit. It has been suggested that they are carried up by the

winged males, but this is probably only an exceptional occurrence; while,

as they are known to be capable of ascending with rapidity by means of

crawling and running, it may be taken for granted that this is the usual

method with them. Some of these wingless females have been found in numbers

on gas-lamps, and are believed to have been attracted by the light, as is

the case with very many of the winged forms.[307] {414}Neither is the

geographical distribution limited by this inferior condition of the most

important of the organs of locomotion, for _Cheimatobia brumata_ (the

Winter-moth) one of the species with flightless female, is a common and

widely distributed Insect in Europe and North America.

Although the classification of this family is based almost entirely on

wing-nervuration, yet there are some divisions of the Geometridae in which

this character is remarkably variable, certain individuals frequently

exhibiting considerable abnormality.[308] _Amphidasis betularia_ is

believed to have changed its variation considerably in the course of the

last fifty years. Previous to that time a black variety of the species was

unknown, but it has now become common; and it is believed that other

species of Geometridae are in process of exhibiting a similar

phenomenon.[309]

FAM. 37. NOCTUIDAE (_Owlet-Moths_, _Eulen_ of the Germans).—This very

extensive assemblage consists of moths rarely seen in the day-time, of

generally sombre colours, with antennae destitute of remarkable

developments in the male (except in a small number of forms); proboscis and

frenulum both present; a complex sense-organ on each side of the body at

the junction of the metathorax and abdomen. The number of species already

known can scarcely be less than 8000; owing to their large numbers and the

great general resemblance of the forms, their classification is a matter of

considerable difficulty. Although the peculiar structure at the base of the

thorax was long since pointed out, it has never received any thorough

investigation. Few other remarkable structures have yet been discovered:

the most interesting is perhaps the peculiarity in the hind wings of the

males of certain Ommatophorinae recently pointed out by Sir G. F.

Hampson[310]: in the genera _Patula_ and _Argiva_ the form of the hind

wings is normal in the females, but in the male the anterior one-half of

each of these wings is aborted, and the position of the nervures changed;

this condition is connected with the development of a glandular patch or

fold on the wing, and is remarkable as profoundly affecting a structure

which is {415}otherwise so constant that the classification of the family

is largely based on it.

[Illustration: Fig. 203—_Brephos notha._ Larva, newly hatched. Britain.]

The larvae are as a rule destitute of the remarkable adornments of hairs

and armatures of spines that are so common in many of the families we have

previously considered; they are fond of concealing themselves during the

day and coming out at night to feed; many of them pass most of their time

at, or beneath, the surface of the ground, finding nourishment in roots or

the lower parts of the stems of plants; this is notably the case in the

genus _Agrotis_, which is perhaps the most widely distributed of all the

genera of moths. Such caterpillars are known as Cut-worms in North

America.[311] The great resemblance, _inter se_, of certain of these

Cut-worms, much astonished the American naturalist Harris, who found that

larvae almost perfectly similar produced very different moths. The majority

of Noctuid larvae have the usual number of legs, viz., three pairs of

thoracic legs, four pairs of abdominal feet and the terminal claspers. In

some divisions of the family there is a departure from this arrangement,

and the abdominal feet are reduced to three, or even to two, pairs. One or

two larvae are known—e.g. _Euclidia mi_—in which the claspers have not the

usual function, but are free terminal appendages. When the abdominal legs

are reduced in number (_Plusia_, e.g.) the larvae are said to be

Half-loopers, or Semi-loopers, as they assume to some extent the peculiar

mode of progression of the Geometrid larvae, which are known as Loopers. In

the case of certain larvae, e.g. _Triphaena_, that have the normal number

of feet, it has been observed that when first hatched, the one or two

anterior pairs of the abdominal set are ill developed, and the larvae do

not use them for walking. This is the case with the young larva of our

British _Brephos notha_ (Fig. 203). Subsequently, however, this larva

undergoes a considerable change, and appears in the form shown in Fig. 204.

This interesting larva joins together two or three {416}leaves of aspen and

lives between them, an unusual habit for Noctuid larvae. When about to

pupate it bores into bark or soft wood to change to a pupa, Fig. 205; the

specimen represented closed the hole of entry by placing two separate doors

of silk across the burrow, as shown at _d_. The anal armature of this pupa

is terminated by a curious transverse process. The systematic position of

this interesting Insect is very uncertain: Meyrick and others associate it

with the Geometridae.

[Illustration: Fig. 204—_Brephos notha._ Adult larva.]

[Illustration: Fig. 205 —_Brephos notha._ A, Pupa, ventral aspect; B,

extremity of body, magnified; C, the pupa in wood; _d_, diaphragms

constructed by the larva.]

The larva of _Leucania unipunctata_ is the notorious Army-worm that commits

great ravages on grass and corn in North America. This species sometimes

increases in numbers to a considerable extent without being observed, owing

to the retiring habits of the larvae; when, however, the increase of

numbers has been so great that food becomes scarce, or for some other

cause—for the scarcity of food is supposed not to be the only reason—the

larvae become gregarious, and migrate in enormous swarms: whence its

popular name. The Cotton-worm, _Aletia xylinae_ is even more notorious on

account of its ravages. Riley states[312] that in bad years the mischief it

commits on the cotton crop causes a loss of £6,000,000, and that for a

period of fourteen successive years the annual loss averaged about

£3,000,000. This caterpillar strips the cotton plants of all but their

branches. It is assisted in its work by another highly destructive Noctuid

caterpillar, the Boll-worm, or larva of _Heliothis armigera_, which bores

into the buds and pods. This {417}latter Insect attacks a great variety of

plants, and has a very wide distribution, being found even in England,

where happily it is always a rare Insect.

In Britain, as well as in parts of Northern Europe, a Noctuid moth,

_Charaeas graminis_, occasionally increases to an enormous extent: its

larva is called the Hill-grub and lives on the grass of pastures,

frequently doing great damage in hill-lands. The increase of this moth

seems to take place after the manner of an epidemic; a considerable number

of years may pass during which it is scarcely seen, and it will then appear

in unusual numbers in widely separated localities. This moth lays a large

number of eggs, and is not completely nocturnal in habits; sometimes it may

be seen on the wing in great numbers in the hottest sunshine, and it has

been noticed that there is then a great disproportion of the sexes, the

females being ten or twenty times as numerous as the males. In Australia,

the Bugong moth, _Agrotis spina_, occurs in millions in certain localities

in Victoria: this moth hibernates as an imago, and it formerly formed, in

this instar, an important article of food with the aborigines. The powers

of increase of another Noctuid moth—_Erastria scitula_—are of great value.

Its habits have been described by Rouzaud.[313] On the shores of the

Mediterranean the larva of this little moth lives on a

Scale-Insect—_Lecanium oleae_—that infests the peach; and as the moth may

have as many as five generations in a year, it commits laudable havoc with

the pest. The larva is of remarkable form, very short and convex, with

small head, and only two pairs of abdominal feet. The scale of the

_Lecanium_ is of larger size than is usual in that group of Insects, and

the young larva of the _Erastria_ buries itself, as soon as hatched, in one

of the scales; it destroys successively numerous scales, and after having

undergone several moults, it finds itself provided, for the first time,

with a spinneret, when, with the aid of its silk, it adds to and adapts a

Coccid scale, and thus forms a portable habitation; this it holds on to by

means of the pair of anal claspers, which are of unusual form. The case is

afterwards subjected to further alteration, so that it may serve as a

protection to the creature when it has changed to a pupa. This moth is said

to be free from the attacks of parasites, and if this be the case it is

probable that its increase is regulated by the fact that {418}when the

creature becomes numerous it thus reduces the food supply, so that its own

numbers are afterwards in consequence diminished.

One of the most remarkable genera of British Noctuidae is _Acronycta_,[314]

the larvae of which exhibit so much diversity that it has been suggested

that the genus should be dismembered and its fragments treated as allied to

several different divisions of moths. There are many points of interest in

connection with the natural history of these _Acronycta_. _A. psi_ and _A.

ridens_ are practically indistinguishable as moths, though the larvae are

easily separated: the former species is said to be destroyed to an amazing

extent by parasites, yet it remains a common Insect. The genus _Apatela_ is

very closely allied to _Acronycta_, and Harris says that "_Apatela_

signifies deceptive, and this name was probably given to the genus because

the caterpillars appear in the dress of Arctians and Liparians, but produce

true owlet-moths or Noctuas."[315] The species of another British genus,

_Bryophila_, possess the exceptional habit of feeding on lichens. Some of

the American group Erebides are amongst the largest Insects, measuring

seven or eight inches across the expanded wings.

The Deltoid moths are frequently treated as a distinct family, Deltoidae,

perhaps chiefly because of their resemblance to Pyralidae. At present,

however, they are considered to be separated from Noctuidae by no valid

characters.

FAM. 38. EPICOPEIIDAE.—The genus _Epicopeia_ consists of only a few moths,

but they are amongst the most extraordinary known: at first sight they

would be declared without hesitation to be large swallow-tail butterflies,

and Hampson states that they "mimic" the Papilios of the _Polyxenus_ group.

Very little is known about these extremely rare Insects, but the larva is

stated, on the authority of Mr. Dudgeon, to surpass the moths themselves in

extravagance; to be covered with long processes of snow-white

efflorescence, like wax, exuded from the skin, and to "mimic" a colony of

the larva of a Homopterous Insect. Some ten species of this genus are known

from Java, India, China, and Japan. In this family there is said to be a

rudimentary frenulum, but it is doubtful whether the hairs that have given

rise to this definition really justify it.

{419}FAM. 39. URANIIDAE.—A family of small extent, including light-bodied

moths with ample wings and thread-like antennae; most of them resemble

Geometridae, but a few genera, _Urania_ and _Nyctalemon_, are like

Swallow-tail butterflies and have similar habits. The Madagascar moth,

_Chrysiridia madagascariensis_ (better known as _Urania rhipheus_), is a

most elegant and beautiful Insect, whose only close allies (except an East

African congener) are the tropical American species of _Urania_, which were

till recently treated as undoubtedly congeneric with the Madagascar moth.

The family consists of but six genera and some sixty species. The question

of its affinities has given rise to much discussion, but on the whole it

would appear that these Insects are least ill-placed near Noctuidae.[316]

The larva of the South American genus _Coronidia_ is in general form like a

Noctuid larva, and has the normal number of legs; it possesses a few

peculiar fleshy processes on the back. A description of the larva of

_Chrysiridia madagascariensis_ has been widely spread; but according to

Camboué,[317] the account of the metamorphoses, first given by Boisduval,

is erroneous. The larva, it appears, resembles in general form that of

_Coronidia_, and has sixteen feet; it is, however, armed with long,

spatulate black hairs; it changes to a pupa in a cocoon of open network.

[Illustration: Fig. 206—Abdomen of _Chrysiridia madagascariensis_. A,

Horizontal section showing the lower part of the male abdomen: 1, first

segment; 2, spiracle of second segment; 4-8, posterior segments. B, the

abdomen seen from the side, with the segments numbered. The section is that

of an old, dried specimen.]

In all the species of this family we have examined, we have noticed the

existence of a highly peculiar structure that seems hitherto to have

escaped observation. On each side of the second abdominal segment there is

an ear-like opening (usually {420}much concealed by overlapping scales),

giving entrance to a chamber in the body; this chamber extends to the

middle line, being separated from its fellow by only a thin partition. At

its anterior and lateral part there is a second vesicle-like chamber,

formed by a delicate membrane that extends as far forwards as the base of

the abdomen. There can be little doubt that this is part of some kind of

organ of sense, though it is much larger than is usual with Insect

sense-organs.

FAM. 40. EPIPLEMIDAE.—Under this name Hampson has assembled certain

Geometroid moths, some of them placed previously in Chalcosiidae, some in

Geometridae. They form a varied group, apparently closely allied to

Uraniidae, and having a similar peculiar sense-organ; but are distinguished

by the presence of a frenulum. The larva seems to be like that of

Uraniidae.

FAM. 41. PYRALIDAE.—This division is to be considered rather as a group of

families than as a family; it includes a very large number of small or

moderate-sized moths of fragile structure, frequently having long legs;

antennae simple, only in a few cases pectinate; distinguished from

Noctuidae and all the other extensive divisions of moths by the peculiar

course of the costal nervure of the hind wing, which either keeps, in the

middle of its course, near to the sub-costal or actually unites with it,

subsequently again separating. Members of the Pyralidae are found in all

lands; in Britain we have about 150 species. The larvae are usually nearly

bare, with only short, scattered setae, and little coloration; they have

most varied habits, are fond of concealment, and are very lively and abrupt

in movement, wriggling backwards as well as forwards, when disturbed; a

cocoon is formed for the metamorphosis.

The family as a whole consists of Insects of unattractive appearance,

although it contains some very elegant and interesting moths and numerous

forms of structural interest. In the genus _Thiridopteryx_ little

transparent spaces on the wings occur as a character peculiar to the males;

the spaces are correlative with a greater or less derangement of the

wing-nervures. In some other forms there is a remarkable retinaculum,

consisting of large scales, and this, too, is connected with a distortion

of the wing-nervures. The Pyralidae—Pyralites of Ragonot,[318] Pyralidina

of {421}Meyrick—have recently been revised by two naturalists of

distinction almost simultaneously; unfortunately their results are

discrepant, Meyrick including Pterophoridae and Orneodidae, and yet

admitting in all only eight families; while Ragonot does not include the

two groups named, but defines seventeen tribes of the two

families—Pyralidae and Crambidae—that he admits.

The Pyraustidae of Meyrick is an enormous division including the

Hydrocampidae and Scopariidae of many authors, as well as the Pyraustinae

proper and a small group of Ragonot's, the Homophysinae. The division

Scopariinae is believed to be amongst the "most ancient" of Lepidoptera;

the food of the larvae consists of moss and lichens. This group is widely

distributed, being richly represented in Australia, New Zealand, and the

Hawaiian Islands, as well as in Europe; and probably really occurs wherever

their food-plants exist accompanied by a tolerable climate. The statistics

of the distribution of this group, so far as at present known, have been

furnished by Mr. Meyrick, as follows:—European region, about 25 species;

Madeira, 3; St. Helena, 6; South Africa, 2 or 3; India, 9; Malayan region,

3 or 4; Australia, 24; New Zealand, 64; Hawaiian Islands, 50; North

America, 17 (one of them European); South America, 10. The

Hydrocampinae—the China-marks—are of great interest, as being amongst the

few forms of Lepidoptera adapted for aquatic life. It is believed that all

their larvae are aquatic, though of only a few is there much known. The

diversity amongst these forms is of considerable interest. The habits of

_Hydrocampa nymphaeata_ were long since described by Réaumur, and have more

recently been dealt with by Buckler,[319] W. Müller[320] and Prof.

Miall.[321] Although there are some discrepancies in their accounts, due we

believe to the observations being made at different periods of the life and

under somewhat different circumstances, yet the account given by Müller is

we feel no doubt substantially correct. The larvae when hatched mine in the

leaves of a water-plant for a short time—thirty hours to three days

according to Buckler—and are completely surrounded by water, which

penetrates freely into their burrows; at this period the caterpillar

breathes by its skin, the spiracles being very small, and the tubes leading

from {422}them closed and functionless. After this brief period of mining

life, the larva moults and then constructs a habitation by cutting a piece

out of a leaf, and fastening it to the under side of another leaf; it is

thus provided with a habitation, but it is one into which the water freely

enters, and the respiratory apparatus remains in the state we have

described. The Insect passes through several moults, and then hibernates in

the water. On its revival in the spring a change occurs, and the larva

constructs a portable, or we should rather say free, habitation out of two

large pieces of leaf of lens-shape, fastened together at the edges; but the

larva has some method of managing matters so that the water can be kept out

of this house; thus the creature lives in air though immersed in the water.

A correlative change occurs in the structure of the skin and tracheal

system. The former becomes studded with prominent points that help to

maintain a coat of air round the Insect, like dry velvet immersed in water;

the spiracles are larger than they were, and they and the tracheal tubes

are open. One or two moults take place and the creature then pupates. There

is a good deal of discrepancy in the accounts of this period, and it seems

probable that the pupa is sometimes aerial, sometimes aquatic. Buckler's

account of the formation of the case shows that the larva first cuts off,

by an ingenious process, one piece of leaf, leaving itself on this, as on a

raft; this it guides to a leaf suitable for a second piece, gets the raft

underneath, and fastens it with silk to the upper portion, and then severs

this, leaving the construction free; afterwards the larva goes through a

curious process of changing its position and working at the two extremities

of the case, apparently with the object of making it all right as regards

its capacity for including air and keeping out water. He believes that

Réaumur was correct in his idea that the larva regulates the admission of

air or of water to the case in conformity with its needs for respiration.

Müller calls special attention to the great changes in habit and in the

structure of the integument during the life of this larva; but the reader

will gather from what we relate as to various terrestrial Lepidopterous

larvae, that these phenomena are not very dissimilar from what frequently

take place in the latter; a change of habits at some particular moult,

accompanied by great changes in the integument, and even in the size of the

stigmata, being of frequent occurrence.

{423}The larva of _Nymphula stagnata_, a close ally of _H. nymphaeata_, has

aquatic habits of a somewhat similar but simpler nature; while _N._

(_Paraponyx_) _stratiotata_ is very different. This larva is provided with

eight rows of tufts of flexible branchiae, occupying the position of the

spots or setigerous warts usual in caterpillars, and reminding one of the

spines of certain butterfly-larvae, though they are undoubtedly respiratory

filaments. These caterpillars protect themselves by forming silken webs or

cases, or by adopting the case of some other larva, and are in the habit of

holding on by the anal claspers, and rapidly and energetically moving the

anterior parts of the body in an undulating fashion. The spiracles exist,

but are functionless. The pupa lives under water, and has no branchiae; but

three of the pairs of abdominal spiracles are open, and project from the

body. Müller informs us that in a Brazilian _Paraponyx_ these three pairs

of spiracles were already large in the larva, though the other pairs were

very small, or absent. He considers that the moth of this species descends

beneath the water of a rapid stream, and fastens its eggs on the stems of

plants therein. _Cataclysta lemnata_ lives in a case of silk with leaves of

duckweed attached to it, or in a piece of a hollow stem of some aquatic

plant; it is believed to breathe, like _H. nymphaeata_, at first by the

integument and subsequently by open stigmata; but particulars as to how it

obtains the requisite air-supply are not forthcoming: the aquatic pupa

breathes by three large abdominal spiracles like _Paraponyx_.

Musotimidae[322] is a small group of two or three genera found in Australia

and Polynesia; and the Tineodidae also consist of only two Australian

genera. Siculodidae is likewise a small Antarctic group, placed by Meyrick

in Pyralidina; but his view is not accepted by Snellen and Ragonot.

Epipaschiinae (formerly treated as a separate family) and Endotrichiinae

are, according to Meyrick, subdivisions of the family Pyralidae proper, an

enormous group of more than 100 genera. The Chrysauginae consist chiefly of

American forms, and have not been treated by Meyrick; some of this group

have been classed with Tortricidae or Deltoidae on account of the

undulating costa of the front wings and the long, peculiar palpi. The

Galleriidae are a small group including Insects that live in bees'-nests,

and feed on the wax {424}etc.; others eat seeds, or dried vegetable

substances. Three out of our five British species of this family occur

(usually gregariously) in bee-hives, and have the peculiar habit of

spinning their cocoons together. The mass of common cocoons formed in this

manner by _Aphomia sociella_ is remarkably tough and enduring; portions of

it are not infrequently picked up, and as the cocoons are of a peculiar

tubular form their nature gives rise to some perplexity.

Phycitidae[323] is another very large assemblage of Insects with very

diverse habits. The frenulum and retinaculum are similarly formed in the

two sexes: the males frequently have the basal-joint of the antennae

swollen; hence the term "Knot-horns" applied by collectors to these moths.

The larvae of the species of _Ephestia_ infest groceries, and most children

have become to a slight extent acquainted with them amongst dried figs;

that of _E. kuehniella_ has become very injurious in flour-mills, its

enormous increase being due in all probability to the fact that the

favourable and equable temperature maintained in the mills promotes a rapid

succession of generations, so that the Insect may increase to such an

extent as to entirely block the machinery. Many of the Phycitidae feed on

the bark of trees in galleries or tunnels constructed partially of silk. A

very peculiar modification of this habit in _Cecidipta excoecaria_ has been

described by Berg.[324] In Argentina this Insect takes possession of the

galls formed by a _Chermes_ on _Excoecaria biglandulosa_, a Euphorbiaceous

tree. The female moth lays an egg on a gall, and the resulting larva bores

into the gall and nourishes itself on the interior till all is eaten except

a thin external coat; the caterpillar then pupates in this chamber. The

galls vary in size and shape, and the larva displays much constructive

ability in adapting its home to its needs by the addition of tubes of silk

or by other modes. Sometimes the amount of food furnished by the interior

of the gall is not sufficient; the larva, in such cases, resorts to the

leaves of the plant for a supplement, but does not eat them in the usual

manner of a caterpillar; it cuts off and carries a leaf to the entrance of

its abode, fastens the leaf there with silk, and then itself entering,

feeds, from the interior, on the food it has thus acquired. Another

Phycitid, _Dakruma coccidivora_ is very {425}beneficial in North America by

eating large Scale-Insects of the _Lecanium_ group, somewhat after the

fashion of _Erastria scitula_; it does not construct a case, but shelters

itself when walking from one scale to another by means of silken tubes; it

suffers from the attacks of parasites.[325] Oxychirotinae, an Australian

group, is interesting because, according to Meyrick, it possesses forms

connecting the Pterophoridae with the more normal Pyralids.

Crambidae, or Grass-moths, are amongst the most abundant Lepidoptera in

this country, as they include the little pale moths that fly for short

distances amongst the grass of lawns and pastures; they fold their wings

tightly to their body, and have a head pointed in front, in consequence of

the form and direction of the palpi. They sit in an upright position on the

stems of grass, and it has been said that this is done because then they

are not conspicuous. Perhaps: but it would be a somewhat difficult

acrobatic performance to sit with six legs across a stem of grass. The

larvae are feeders on grass, and construct silken tunnels about the roots

at or near the surface. The Ancylolominae are included in Crambidae by

Meyrick and Hampson. Schoenobiinae[326] are included by Meyrick in

Pyraustidae, but this view appears not to meet with acceptance, and the

group is more usually associated with the Crambidae. Most writers place the

anomalous genus _Acentropus_ as a separate tribe, but it is associated by

both Meyrick and Hampson with _Schoenobius_. This Insect is apparently the

most completely aquatic of all the Lepidoptera, and was for long associated

with the Trichoptera in consequence of its habits and of the scaling of the

wings being of a very inferior kind. The males may sometimes be found in

large numbers fluttering over the surface of shallow, but large, bodies of

water; the females are rarely seen, and in some cases have no wings, or

have these organs so small as to be useless. The female, it would appear,

comes quite to the surface for coupling, and then takes the male beneath

the water. The larvae have the usual number of Lepidopterous feet, and

apparently feed on the leaves of plants below water just as Lepidopterous

larvae ordinarily do in the air.[327] They have no trace of gills, and

their {426}mode of respiration is unknown. A great deal has been written

about these Insects, but really very little is known. They are abundant,

though local in many parts of North and Central Europe; some of the females

have, as we have said, abbreviated wings, but how many species there are,

and whether the modifications existing in the development of the wings are

constant in one species or locality, are unknown as yet.

FAM. 42. PTEROPHORIDAE[328] (_Plume-moths_).—Elegant Insects of small size,

usually with the wings divided (after the fashion of a hand into fingers)

so as to form feathers: the extent of this division is diverse, but the

hind wings are more completely divided than the front, which indeed are

sometimes almost entire. The group is placed by Meyrick in his Pyralidina,

but there are many entomologists who look on it as distinct. It consists of

two sub-families, Agdistinae and Pterophorinae, that have been treated as

families by many entomologists. The Agdistinae (of which we have a British

representative of the only genus _Agdistes_) have the wings undivided.

Pterophorinae have the hind wings trifid or (rarely) quadrifid, the front

wings bifid or (rarely) trifid. The larvae of the Pterophorinae are

different from those of Pyralidae, being slow in movement and of heavy

form, covered with hair and living exposed on leaves; the pupae are highly

remarkable, being soft, coloured somewhat like the larvae, and also hairy

like the larvae, and are attached somewhat after the manner of

butterfly-pupae by the cremaster: but in some cases there is a slight

cocoon. There is, however, much variety in the larval and pupal habits of

the Pterophoridae, many having habits of concealment of divers kinds. We

have thirty species of these lovely Plume-moths in Britain. The family is

widely distributed, and will probably prove numerous in species when the

small and delicate Insects existing in the tropics are more appreciated by

collectors.

FAM. 43. ALUCITIDAE (ORNEODIDAE of Meyrick and others).—The genus _Alucita_

includes the only moths that have the front and hind wings divided each

into six feathers. Species of it, though not numerous, occur in various

regions. The larva and pupa are less anomalous than those of the

Pterophoridae, though the imago is more anomalous. The caterpillar of our

British _A. polydactyla_ feeds on the flower-buds of honey-suckle, and

forms a {427}cocoon. The moth with wings expanded is about an inch across,

and is a lovely object. It is not rare, though seldom numerous.

FAM. 44. TORTRICIDAE.—Moths of small size, with a rather ample wing area,

with the wing-fringes never as long as the wings are wide (long across),

the hind wings without a pattern: the anterior nervure on the hind wings is

simply divergent from that next to it, and the internal nervure, 1b, is

very evidently forked at the base. The larvae inhabit their food, which may

be rolled up or twisted leaves, or the interior of fruits and herbs, or

galls, or even roots; they exhibit less diversity than is usual in other

large series of moths; all have the normal complement of sixteen legs. This

group is a very extensive one, but is much neglected owing to the great

difficulties attending its study; it is not recognised in Hampson's Table

of families given on p. 370, being there merged in Tineidae. It appears,

however, to be a really natural group, and it is not desirable to merge it

in the sufficiently enormous assemblage of the Tineidae till this has been

shown to be necessary by the light of a greater knowledge of the external

anatomy than we possess at present. The term Microlepidoptera is frequently

met with in entomological literature, and should, we think, be confined to

the two series Tortricidae and Tineidae. The Pterophoridae, and even the

Pyralidae, have been, and still sometimes are, included under this term,

but at present it seems best to limit its application as is here suggested.

Three great divisions are at present recognised; these were formerly called

by Meyrick,[329] Tortricidae, Grapholithidae, Conchylidae;

subsequently,[330] he has adopted the names Tortricidae, Epiblemidae,

Phaloniadae. Lord Walsingham, who has devoted a great deal of time and

study to the elucidation of this most difficult group, has suggested[331]

that another change is desirable, and if so the nomenclature will be:—1.

Tortricidae [or Tortricinae, according to the view that may be taken as to

the group being family or sub-family]; 2. Phaloniidae [= the formerly used

name, Conchylidae]; 3. Olethreutidae [= the formerly used name

Grapholithinae = Epiblemidae, Meyr.]. We have upwards of 300 species in

Britain, nearly 200 of which belong to the last division. The name

Tortricidae refers to the habit the {428}larvae of these moths possess of

rolling up leaves, or twisting and distorting shoots and buds.

The mode in which leaves and shoots are twisted and rolled by the very

small larvae has been much discussed and is probably the result of two or

three distinct causes:—1, the immediate operations of the larva; 2, the

contraction of silk when drying; 3, changes in the mode of growth of the

parts of the vegetable, resulting from the interference of the caterpillar.

The larvae of this family that live in fruits are only too widely (we will

not say well) known. Stainton gives as the habitat of _Epinotia funebrana_,

"larva frequent in plum-pies"; the caterpillar of _Carpocapsa pomonella_

(the Codling-moth) mines in apples and pears, and its ravages are known

only too well in widely distant parts of the world where fruit-trees of

this kind are cultivated. _C. splendana_ lives in acorns and walnuts; _C.

juliana_ in Spanish chestnuts. Two, if not more, larvae live in the seeds

of Euphorbiaceous plants, and have become notorious under the name of

jumping-beans, on account of the movements they cause. As these latter show

no trace externally of being inhabited, the movements are supposed to be a

mysterious property of the seed; they are really due to its containing a

large cavity, extending, in one direction of the seed, nearly or quite from

skin to skin; in this the larva makes a movement sufficient to alter the

point of equilibrium of the quiescent seed, or as a free body to strike

some part of it. The exact nature of the movements of the larva have not,

we believe, been ascertained. There are, at least, two species of these

Insects, and two plants harbouring them, known in the United States and

Mexico, viz. _Carpocapsa saltitans_ living in the seeds of _Croton

colliguaja_ and _Grapholitha sebastianiae_ living in the seeds of

_Sebastiania bicapsularis_.

FAM. 45. TINEIDAE.—Small moths with the labial palpi more flexible and

mobile than in other moths; usually separated and pointed. Hind wings

frequently with very long fringes, the wing itself being proportionally

reduced in size, and in consequence pointed at the tip. Larvae very

diverse, almost always with habits of concealment. The series of forms

included under this head is very numerous, the British species alone

mounting up to 700, while the total described cannot be less than 4000.

This number, however, must be but a fragment of what exists, if Mr. Meyrick

be correct in supposing that a single one of the divisions of the

family—Oecophoridae—comprises 2000 species in Australia and New Zealand

alone.

{429}[Illustration: Fig. 207—_Diplosara lignivora_ (Gelechiides). Hawaiian

Islands.]

As the study of these Insects is attended with great difficulty on account

of their fragility and the minute size of the great majority, it is not a

matter for surprise that their classification is in a comparatively

rudimentary state. We shall not, therefore, deal with it here. Neither can

we attempt to give any idea of the extreme diversity in the colours, forms,

and attitudes of these small Insects. The one shown in Fig. 207, is

remarkable on account of the great accumulation of scales on the wings and

legs. As regards the pointed wings and the long fringes, we may remark that

it is probable that in many of these small forms the wings are passive

agents in locomotion; a similar condition of the wings is found in other

very minute Insects, _e.g._ Thysanoptera and Trichopterygidae; in all these

cases the framework of the wings is nearly absent: in some forms of the

Tineidae, _Opostega_, e.g. the nervules are reduced to three or four in

each wing. The variety in habits is as great as that of the external form,

and the larvae exceed in diversity those of any other group of Lepidoptera.

No doubt a corresponding amount of diversity will be discovered in the

details of structure of the perfect Insects, the anatomy of but few having

been at present investigated. _Tinea pellionella_ has two very important

peculiarities in its internal anatomy: the testes consist of four round

follicles on each side, and, contrary to the condition generally prevalent

in Lepidoptera, are not brought together in a common capsule: the two

groups are, however, not quite free (as they are in _Hepialus_), but are

connected by a loose tracheal network. Even more remarkable is the fact

also pointed out by Cholodkovsky[332] that the adult Insect possesses only

two Malpighian tubes instead of six, the normal number in Lepidoptera; in

the larva there are, however, six elongate tubes. The group of forms to

which {430}_Tinea_ belongs is remarkable for the diversity and exceptional

character of the food-habits of the larvae; species subsist on dried

camel's dung, various kinds of clothes, furs, and hair, and even about

horns of deer and horses' hoofs: one species has been found in abundance in

the hair of a live sloth, _Bradypus cuculliger_, under circumstances that

render it possible that the larva feeds on the creature's hair, though it

may feed on minute vegetable matter found in the hair. The larva of _Tinea

vastella_ is occasionally found feeding on the horns of living antelopes.

Several species of Tineidae are known to devour Scale-Insects.

_Lita solanella_ is notorious for the ravages it commits on stored

potatoes. Quite a number of species live on cryptogamic matter, or in old

wood; _Oinophila v-flavum_ feeds on the mould on the walls of cellars, and

is reputed to be injurious by occasionally also attacking the corks of

bottles containing wine. _Oecocecis guyonella_ is said to be the cause of

galls on _Limoniastrum guyonianum_, a plant that, growing in the deserts to

the south of Algeria, is a favourite food of camels, and is frequently

entirely covered with sand. The deposition of an egg by this moth is

believed by Guénée[333] to give rise to a gall in which the larva is

entirely enclosed (like the larvae of the gall-flies). Of Clothes-moths

there are at least three species widely distributed. _Trichophaga

tapetzella_ is perhaps entitled to be considered the Clothes-moth; its

caterpillar not only feeds on clothes, but spins webs and galleries amongst

them. _Tinea pellionella_ is also very common; its larva lives in a

portable case, while that of the third species, _Tineola biselliella_,

forms neither a case nor definite galleries. We have found this the most

destructive of the three at Cambridge. Clothes or valuable furs may be

completely protected by wrapping them in good sound paper in such a way

that no crevices are left at the places where the edges of the paper meet.

Garments that have become infested may be entirely cleared by free exposure

to air and sunshine.

Two species of _Tinea_ have been recorded as viviparous, viz. _Tinea

vivipara_ in Australia, and an undetermined species in South America. The

species of the genus _Solenobia_—in which the female is apterous—are

frequently parthenogenetic. The group Taleporiidae, to which this genus

belongs, is by some {431}classified with Psychidae, in which family, as we

have pointed out, one or two parthenogenetic forms are also known.

The larvae of Tineidae, though they do not exhibit the remarkable armature

found in so many of the larger caterpillars, are exceedingly diverse.[334]

Some are entirely destitute of feet (_Phyllocnistis_). Others are destitute

of the thoracic legs; _Nepticula_ is in this case, but it is provided with

an increased number of abdominal feet, in the form of more or less

imperfect ventral processes. Some mine in leaves, others live in portable

cases of various forms. Some are leaf-miners during their early life, and

subsequently change their habits by constructing a portable case. The genus

_Coleophora_ affords numerous instances of this mode of life; the habits of

these case-bearers exhibit considerable variety, and there are many points

of interest in their life-histories. Change of habit during the larval life

has already been alluded to as occurring in many Lepidoptera and is nowhere

more strikingly exemplified than in certain Tineidae. Meyrick mentions the

following case as occurring in an Australian Insect, _Nematobola

orthotricha_;[335] the larva, until two-thirds grown, is without feet, and

is almost colourless, and mines in the leaves of _Persoonia lanceolata_;

but when two-thirds grown it acquires sixteen feet, changes colour,

becoming very variegate, and feeds externally, unprotected, on the leaves.

The cases of the case-bearing Tineids are usually of small size, and do not

attract attention like those of Psychidae. A very remarkable one was

discovered by Mr. E. E. Green in Ceylon, and was at first believed to be

formed by a Caddis-worm. It has now been ascertained that the Insect

forming it is the caterpillar of _Pseudodoxia limulus_, a Tineid moth of

the group Depressariidae;[336] the case is composed of minute fragments of

moss, sand, and lichens; the anterior end is dilated into a shield-like

hood that covers and protects the anterior parts of the larva when feeding;

the food is mosses and lichens on rocks and trees. Before pupating, the

larva folds down the edges of the hood over the mouth of the tube, like an

envelope, fastening them with silk. The case is fixed to the rock or other

support and hangs there until the moth appears.

{432}[Illustration: Fig. 208—_Pronuba synthetica_. North America. A, Larva;

B, C, pupa, ventral and lateral aspects; D, female moth; E, head and part

of thorax of the female moth: _a_, labial palp; _b_, maxillary tentacle;

_c_, maxillary palp; _d_, proboscis; _e_, base of front leg. (After

Riley.)]

The family Prodoxidae consists of some Tineids, the larvae of which feed in

the pods and stems of the Yuccas of south-western North America; they have

the mouth of very unusual form (Fig. 208, E), and some of them, by aid of

this peculiar mouth, exhibit a remarkable modification of instinct. The

facts are chiefly known from the observations of Riley[337] on _Pronuba

yuccasella_, a moth living on _Yucca filamentosa_; this plant has been

introduced into our gardens in this country, where it never, we believe,

produces seed. The Yuccas are not fitted for self-fertilisation or for

fertilisation by Insect agency of an ordinary kind. The progeny of the moth

develops in the pods of the plant, and as these cannot grow until the

flowers have been fertilised, the moth has the habit of fertilising the

flowers at the time she lays her egg in the part that is to develop into

the pod, and to be the food for her own progeny. The female moth first

visits the stamens, and collects, by the aid of the {433}maxillae (which in

this sex are very remarkably formed),[338] a considerable mass of pollen,

which she holds by means of the peculiar maxillary tentacles; she then lays

an egg in the pistil, usually of some flower other than that from which she

has gathered the pollen; and after she has accomplished this act she

carefully applies the pollen she had previously collected to the pistil, so

as to secure the fertilisation of the flower and the development of the

pod.

The species of _Prodoxus_ stand in a very peculiar relation to _Pronuba_.

They also live in Yuccas, and have habits similar to those of _Pronuba_,

with the important exception that, being destitute of the requisite

apparatus, they do not fertilise the Yucca-flowers, and are thus dependent

on _Pronuba_ for the steps being taken that are necessary for the rearing

of the progeny of the two kinds of moth. Hence the name of Yucca-moth has

been bestowed on _Pronuba_, and that of "bogus Yucca-moth" on the

_Prodoxus_. The _Pronuba_ we figure is the largest and most remarkable

species of the genus and fertilises _Yucca brevifolia_; the larva is

destitute of abdominal feet, and in the pupa the spines on the back that

exist in nearly all pupae that live in stems are developed to an

extraordinary extent. The Yuccas do not flower every year, and the

Prodoxidae have a corresponding uncertainty as to their periods of

appearance, passing sometimes a year or two longer than usual in the pupal

stage.

FAM. 46. ERIOCEPHALIDAE.—This family has recently been proposed for some of

the moths formerly included in the genus _Micropteryx_.[339] They are

small, brilliant, metallic Insects, of diurnal habits, but are very rarely

seen on the wing, and it is doubtful whether they can fly much. These

little Insects are of peculiar interest, inasmuch as they differ from the

great majority of the Lepidoptera in at least two very important points,

viz. the structure of the wings and of the mouth-parts. The mouth shows

that we may consider that the Lepidoptera belong to the mandibulate

Insects, although in the great majority of them the mandibles in the final

instar are insignificant, functionless structures, or are entirely absent,

and although the maxillae are so highly adapted for the tasting of sweets

that it is difficult to recognise in them the parts usually found in the

maxilla of mandibulate Insects.

{434}[Illustration: Fig. 209.—Larva of _Eriocephala calthella_. (After

Chapman.) A, Young larva from side, × 50; B, portion of skin with a bulla

or ball-like appendage: C, abdominal foot of larva.]

_Eriocephala_ in both these respects connects the Lepidoptera with

Mandibulata: the mandibles have been shown by Walter[340] to be fairly well

developed; and the maxillae are not developed into a proboscis, but have

each two separate, differentiated—not elongated—lobes, and an elongate,

five-jointed, very flexible palpus. The moths feed on pollen, and use their

maxillae for the purpose, somewhat in the style we have mentioned in

Prodoxidae. The wings have no frenulum, neither have they any shoulder, and

they probably function as separate organs instead of as a united pair on

each side: the modification of the anterior parts of the hind wing—whereby

this wing is reduced as a flying agent to the condition of a subordinate to

the front wing—does not here exist: the hind wing differs little from the

front wing in consequence of the parts in front of the cell being well

developed. There is a small jugum. These characters have led Packard to

suggest that the Eriocephalidae should be separated from all other

Lepidoptera to form a distinct sub-Order, Lepidoptera Laciniata.[341] The

wing-characters of _Eriocephala_ are repeated—as to their main features—in

Hepialidae and Micropterygidae; but both these groups differ from

_Eriocephala_ as to the structure of the mouth-parts, and in their

metamorphoses. Although _Eriocephala calthella_ is one of our most abundant

moths, occurring in the spring nearly everywhere, and being easily found on

account of its habit of sitting in buttercup-flowers, yet its metamorphoses

were till recently completely unknown. Dr. Chapman has, however, been able

to give us some information as to the habits and structure of the larvae,

in both of which points the creature is most interesting. The eggs and

young larvae are "quite {435}unlike our ideas of a Lepidopterous Insect;"

the former have a snowy or mealy appearance, owing to a close coating of

minute rods standing vertically on the surface of the egg, and often tipped

with a small bulb. The larva lives amongst wet moss and feeds on the

growing parts thereof; it is not very similar to any other Lepidopterous

larva: Dr. Chapman suggests a similarity to the Slug-worms (Limacodids),

but Dyar is probably correct in thinking the resemblances between the two

are unimportant: the larva of _Eriocephala_ possesses three pairs of

thoracic legs, and eight pairs of abdominal appendages, placed on the

segments immediately following the thorax; on the under-surface of the

ninth and tenth abdominal segments there is a sucker, trifoliate in form;

this is probably really situate entirely on the tenth segment: the body

bears rows of ball-appendages, and the integument is beautifully

sculptured. The head is retractile and the antennae are longer than is

usual in caterpillars. This larva is profoundly different from other

Lepidopterous larvae inasmuch as the abdominal feet, or appendages, are

placed on different segments to what is customary, and are of a different

form. Unfortunately the pupa has not been procured, but there is some

reason for supposing that it will prove to be more like that of Tineidae

than like that of Micropterygidae.

The New Zealand genus _Palaeomicra_ is only imperfectly known. Meyrick

considers it the "most ancient" Lepidopteron yet discovered; and it would

appear that its relations are with _Eriocephala_ rather than with

_Micropteryx_. From information he has kindly given to us, we are able to

say that this moth possesses mandibles but no proboscis.

[Illustration: Fig. 210—Larva of _Micropteryx_ sp. A, Ventral view of the

larva, magnified; B, the same, with setae unduly magnified. Britain.]

FAM. 47. MICROPTERYGIDAE.—Small moths of metallic colours, without

mandibles, with elongate maxillary palpi: without frenulum: both wings with

a complex system of wing-veins: on the hind wings the area anterior to the

cell is large, and traversed by three or four elongate, parallel veins.

{436}[Illustration: Fig. 211—Pupa of _Micropteryx_ (_semipurpurella_?). A,

Dorsal aspect; B, C, D, views of head dissected off; B, profile; C,

posterior, D, anterior aspects; _m_, mandibles. Britain.]

There are no mandibles, but there is a short, imperfect proboscis. Larva

(Fig. 210) without any legs, mining in leaves. The pupa (Fig. 211) is not a

pupa obtecta, but has the head and appendages free, and is provided with

enormous mandibles. Although these Insects in general appearance resemble

_Eriocephala_ to such an extent that both have been placed in one genus,

viz. _Micropteryx_, yet the two forms are radically distinct. The most

remarkable point in _Micropteryx_ is the metamorphosis; the female moth is

furnished with a cutting ovipositor, by the aid of which she deposits an

egg between the two layers of a leaf after the manner of a saw-fly;[342]

the larva mines the newly-opened leaves in the early spring, and feeds up

with rapidity; it by some means reaches the ground, and there pupates in a

firm but thin cocoon, with grains of earth fastened to it; in this it

passes the greater part of its life as a larva, changing to a pupa very

early in the following spring. The pupa is unlike any other Lepidopterous

pupa, but is similar to those of Trichoptera; neither the head nor the

appendages are glued to the body or to one another, but are free, so that

the pupa can use the appendages to a considerable extent; it is furnished

with enormous mandibles (Fig. 211, C, D), which are detached and shed after

emergence.[343] In the interval between {437}the larval period of feeding

and the imaginal instar, the phenomena of life are essentially like those

of Trichoptera. The larva has not been at all satisfactorily studied; the

spiracles appear to be excessively minute, but have been ascertained by Dr.

Chapman to be normal in number and position.

All the information we possess points to profound distinctions between

_Micropteryx_ and _Eriocephala_, for whereas in the former the mandibles

drop off from the pupa, so that the imago has no mandibles, in the latter

the mandibles exist, as they do in several other true Lepidoptera. As the

history of the mandibles is not known in other Lepidoptera (where they are

present in the larva but wanting in the imago), it is premature to conclude

that no other Lepidoptera suffer the actual loss of the mandibles as

_Micropteryx_ does, though there is nothing to lead us to believe that in

any other Lepidopterous pupa are the mandibles specially developed as they

are in _Micropteryx_. This pupa is in fact quite unique in this Order of

Insects. When the history of the pupal mandibles is known, we shall be able

to decide whether they are secondary structures, like the deciduous,

supplementary mandibles found in Otiorhynchides (Coleoptera, Rhynchophora).

{438}CHAPTER VII

DIPTERA—OR FLIES; APHANIPTERA—OR FLEAS; THYSANOPTERA—OR THRIPS

ORDER VII. DIPTERA

_Wings two, membranous, usually transparent and never very large; behind

the wings a pair of small erect capitate bodies—halteres—frequently

concealed under membranous hoods. No distinct prothorax, all the

divisions of the thorax being united to form a large mass. Mouth-parts

very variable, formed for suction not for biting, frequently assuming the

form of a proboscis that can be retracted and concealed in a cleft of the

under side of the head. The metamorphosis is very great, the larvae

bearing no resemblance whatever to the perfect Insects, but being usually

footless grubs or maggots; frequently the head is indistinct, small, and

retracted. Pupa variable, either exposed and rather hard, with the

appendages of the body more or less adherent; or enclosed in a scaly

capsule looking like a seed, and when extracted, soft and delicate, with

the appendages not fastened to the body incapable of movement._

This definition of the Diptera, or two-winged flies, is framed without

reference to the fleas, which are wingless, or to a few other parasitic

wingless Diptera, such as the sheep-tick. Although the Order is of enormous

extent, these exceptional cases are remarkably few. About 40,000 species of

Diptera have been discovered, but these are only a tithe of what are still

unknown to science. The Order is not a favourite one with entomologists,

and by the rest of the world it may be said to be detested. Flies do not

display the sort of intelligence we appreciate, {439}or the kind of beauty

we admire, and as a few of the creatures somewhat annoy us, the whole Order

is only too frequently included in the category of nuisances that we must

submit to. Moreover, the scavenger-habits that are revealed, when we begin

to study their lives, are very repugnant to many persons. It is therefore

no wonder that flies are not popular, and that few are willing to study

them, or to collect them for observation. Nevertheless, Diptera have

considerable claims to be classed as actually the highest of Insects

physiologically, for it is certainly in them that the processes of a

complete life-history are carried on with the greatest rapidity and that

the phenomena of metamorphosis have been most perfected. A maggot, hatching

from an egg, is able to grow with such rapidity that the work of its life

in this respect is completed in a few days; then forming an impenetrable

skin it dissolves itself almost completely; solidifying subsequently to a

sort of jelly, it in a few days reconstructs itself as a being of totally

different appearance and habits, in all its structures so profoundly

changed from what it was that the resources of science are severely taxed

to demonstrate any identity of the organs of the two instars.

[Illustration: Fig. 212—A Dipteron (Fam. Syrphidae), _Cheilosia

chrysocoma_. Britain. A, Adult larva; B, the pupa; C, nymph, extracted from

pupa; D, imago. (From Weyenbergh.)]

A good study of the comparative anatomy of Diptera has never been made;

Baron Osten Sacken, one of our most accomplished Dipterologists, has

recently stated that "the external characters of the Diptera have as yet

been very insufficiently studied." We shall therefore only trouble the

student with a few observations on points of structure that are of special

importance, or that he will find frequently alluded to. The head is

remarkable {440}for its mobility, and is connected with the thorax by a

slender concealed neck that permits the head to undergo semi-rotation. A

large part—sometimes nearly the whole—of the exposed surface of the head is

occupied by the faceted eyes. It is usually the case that the eyes are

larger in the male than in the female, and the sexual discrepancy in this

respect may be very great. When the eyes of the two sides meet in a

coadapted line of union the Insect is said to be "holoptic," and when the

eyes are well separated "dichoptic."[344] The holoptic condition is

specially characteristic of the male, but in some forms occurs in both

sexes. There is no definite distinction between holoptic and dichoptic

eyes. The eyes may be enormous, Fig. 238, without actually uniting, and in

the cases where actual contiguity occurs, it takes place in different

manners.[345] The eyes are frequently during life of brilliant colours and

variegate with stripes or spots; this condition disappears speedily after

death, and it is uncertain what the use of this coloration may be.[346] The

eyes are frequently densely set with hairs between the almost innumerable

facets. These facets frequently differ in size according to their position

in the organ. The curious double eye of the male _Bibio_ (cf. Fig. 224) is

well worth notice. There are usually three small ocelli placed very near

together on the middle of the summit of the head.

The antennae are of considerable importance, as they offer one of the

readiest means of classification. The families placed by systematists at

the commencement of the Order have antennae similar to those of the

majority of Insects, inasmuch as they consist of a series of segments

approximately similar to one another, and arranged in a linear manner (Fig.

213, A). The number of these joints is never very great, but reaches

sixteen in certain Tipulidae, and falls as low as eight in some Bibionidae.

In certain cases where the antennae of the male are densely feathered

(_Chironomus_, e.g.), the number of joints is in that sex greatly

augmented, but they are imperfectly separated. This form of antenna gives

the name Nemocera to the first series of Diptera.

{441}[Illustration: Fig. 213—Antennae of flies. A, The two antennae of

_Glaphyroptera picta_ (Mycetophilidae); B, antenna of _Hexatoma pellucens_

(Tabanidae); C, of _Asilus crabroniformis_ (Asilidae); D, of _Leptis

scolopacea_ (Leptidae); E, of _Dolichopus undulatus_ (Dolichopidae); F, of

_Volucella bombylans_ (Syrphidae). (After Wandolleck.)]

The majority of flies have antennae of another form, peculiar to the Order,

viz. three segments, the outer one of which is of diverse form, according

to the genus or species, and bears on its front a fine projecting bristle,

frequently feathered, as in Fig. 213, F; and often distinctly divided into

two or more joints. This form of antenna is found in the series Aschiza and

Schizophora; it is well exemplified in the common house-fly, where the

organs in question hang from the forehead, and are placed in a hollow

formed for their reception on the front of the head. Flies with this form

of antennae are called Athericerous. Between the two forms of antennae we

have mentioned there exists what may, speaking roughly, be called an

intermediate condition, or rather a variety of intermediate conditions,

associated in the series Brachycera (Fig. 213, B to D).[347] Here there are

three (sometimes one or two) segments and a terminal appendage, but the

appendage is usually compound (often so distinctly compound that it is

evidently a series of partially, or even completely, separate joints, Fig.

213, B): the appendage in these cases is terminal, that is to say it is

placed, not as in the Eumyiidae on the front of the joint that bears it,

but (in the great majority of Brachycera) at the tip thereof; this

appendage is often conical and pointed, often hair-like. Exceptional forms

of antenna are found in the parasitic flies of the series Pupipara. In the

Order generally the two basal joints of the antennae are evidently distinct

in function from the others, and form the "scape"; the {442}part of the

antenna beyond the scape is called the "flagellum"; an appendage of the

flagellum is called "arista" when bristle-like, when thicker "style." In

the basal joint of the antenna there is a complex nervous structure known

as Johnston's organ. It is specially well developed in _Culex_ and

_Chironomus_, and is larger in the male than it is in the female. Child has

found something of the kind present in all the Diptera he has examined, and

he considers that an analogous structure exists in Insects of other Orders.

He thinks it is concerned with the perception of vibration, there being no

sharp distinction between auditory and tactile sensation.[348]

About one-half of the Diptera possess a peculiar structure in the form of a

head-vesicle called "ptilinum." In the fly emerging from the pupa this

appears as a bladder-like expansion of the front of the head; being

susceptible of great distension, it is useful in rupturing the hard shell

in which the creature is then enclosed. In the mature fly the ptilinum is

completely introverted, and can be found only by dissection; a little

space, the "lunula," just under an arched suture, extending over the point

of insertion of the antennae remains, however, and offers evidence of the

existence of the ptilinum. This structure is also of importance in

classification, though, unfortunately, it is difficult to verify.[349]

No point of Insect morphology has given rise to more difference of opinion

than the mouth of Diptera; and the subject is still very far from being

completely understood. The anatomy and morphology of the mandibulate

Insect-mouth are comparatively simple (though not without greater

difficulties than are usually appreciated); and it has been the desire of

morphologists to homologise the sucking mouth of Diptera with the biting

mouth; hence the view that the appendages of three segments are separate

and distinct in the fly's mouth is taken for granted, and it is further

assumed that some of the secondary parts of the appendages of the biting

mouth can also be recognised in the sucking mouth. The anatomy of the

mouth-parts is, however, {443}subject to great diversity of structure

within the limits of the Order itself, even the two sexes in some species

differing profoundly in this respect.[350] In the majority of the family

Oestridae the mouth-parts are practically absent, and no definite entry to

the alimentary canal can be perceived (Fig. 245). Besides this condition

and its antithesis (Fig. 214), the complex assemblage of lancets seen in

the Breeze-flies that draw blood, there is a great variety of other

anatomical conditions.

[Illustration: Fig. 214.—Mouth-parts of the common blood-sucking fly,

_Haematopota pluvialis_ ♀. A, Viewed from beneath, the proboscis removed;

_a_, labrum; _b_, _b_, cultelli (mandibles of other anatomists); _c_, _c_,

scalpella (maxillae of other anatomists); _d_, part of ventral scutum of

second metamere; _e_, _e_, _f_, _f_, parts of palpi; _g_, hypopharynx and

pellucid salivary duct; _h_, salivary receptacle; _i_, salivary duct; _k_,

membranous part of second metamere; _l_, pharynx: B, labrum, pharynx,

hypopharynx, separated, seen from beneath; _a_, labrum; _b_, hypopharynx;

_c_, salivary duct; _d_, pharynx; _e_, protractor muscles: C, proboscis

(labium) from beneath; _a_, scutum proboscidis; _c_, _c_, labella; _d_,

_d_, retractor muscles. (After Meinert).]

Although, as we have said, great diversity of opinion exists, yet on the

whole the majority of Dipterologists accept a view something to the

following effect:—the labrum, or the labrum combined with the epipharynx,

is frequently much prolonged; the tongue—hypopharynx—may also be much

prolonged, and may form, in apposition with the labrum, a more or less

imperfect tube for ingestion of the nutriment; the labium is more or less

membranous or fleshy, and acts as a sheathing organ, its tips—called

labella—-being in some cases developed to a quite extraordinary extent. As

to the other parts of the mouth there is less agreement; the pointed organs

(Fig. 214, A, _b_ _b_) are by {444}many identified as mandibles, while

another pair of pointed processes (_c_ _c_) are considered to be parts of a

maxilla, and the palpi (_f_ _f_) are by some considered to be maxillary

palps. The Danish entomologist, Meinert, has published the best anatomical

description of many of the diverse kinds of Dipterous mouth.[351] He,

however, takes a different view of the morphology; he considers that not

only may parts of the appendages of the mouth be much modified during the

early stages of the individual development, but that they may be

differently combined, even parts of the appendages of two segments being

brought together in intimate combination. He has also pointed out that the

mandibulate and sucking mouth are mechanical implements constructed on

opposed principles; the main object of a biting mouth being the fixing and

perfecting of the articulations of the mouth, so that great power of

holding may be attained with a limited but definite power of movement. In

the sucking mouth the parts are intimately associated for simple

protrusion. Hence the two kinds of mouth must have been distinguished very

early in the phylogeny, so that we must not expect to find a great

correspondence between the parts of biting and sucking mouths. He

apparently also considers that not only the appendages of a head-segment,

but also part of the body of the segment, may be used in the construction

of the mouth-organs. Meinert's views allow a much greater latitude of

interpretation of the parts of the Dipterous mouth; had he contented

himself with enunciating them in the manner we have followed him in

summarily describing, they would have been recognised as a formidable

obstacle to the facile adoption of the ordinary views. He has, however,

accompanied his general statement with a particular interpretation and a

distinct nomenclature, neither of which is it possible to adopt at present,

as they have no more justification than the ordinary view. So that instead

of one set of doubtful interpretations we have two.[352] In so difficult a

question as homologising the trophi of different Orders of Insects we ought

to use {445}exhaustively every method of inquiry: and from this point of

view the development is of great importance. This has, however, as yet

thrown but little light on the subject, this study being a very difficult

one owing to the profound changes that take place during metamorphosis, the

diversity of the parts in the early stages of Diptera, and the possibility

that the larval conditions may themselves have been greatly changed in the

course of the phylogeny. Miall informs us, however, that in _Chironomus_ as

well as in _Corethra_ the new parts of the mouth of the imago are developed

within those of the larva.[353] This may permit of an identification of the

main divisions of the mouth, at any rate in these cases. Lowne has to some

extent traced the development in the blowfly, and he does not agree with

the usual interpretation of the parts in the adult.

The mouth is of considerable importance in the classification of Diptera.

The Nemocera are remarkable from the linear development and flexibility of

the palpi, which are nearly always at least three- or four-jointed; this

condition occurring in no other Diptera. The palpi attain an extraordinary

development in some Culicidae; in the genus _Megarrhina_ they are nearly as

long as the body, and project in front of the head after the fashion of the

palpi of Lepidoptera. In the Brachycera the sclerites or hard parts of the

mouth reach a maximum of development, and in Tabanidae (Fig. 214),

Nemestrinidae and Bombyliidae are often quite disproportionate to the size

of the Insect. In many of the Eumyiid flies the soft parts are greatly

developed, and capable of a variety of movement, the proboscis as a whole

being protrusible, and having an elbow-joint in the middle.

The thorax is remarkable from the absence of distinct separation into the

three divisions that may usually be so easily distinguished in Insects. The

perfect combination of the three segments adds much to the difficulty of

arriving at general conclusions as to the identification of the parts;

hence considerable difference of opinion still prevails. It was formerly

supposed that a segment from the abdomen was added to the thorax of Diptera

as it is in Hymenoptera, but this has been shown by Brauer to be erroneous.

Indeed, according to Lowne, the abdominal cavity is increased by the

addition of the small posterior area of the thorax; it being the

mesophragma that separates the {446}second and third great divisions of the

body-cavity. The prothorax is always small, except in a few of the abnormal

wingless forms (_Melophagus_); in _Nycteribia_ (Fig. 248) the mesothorax

forms the anterior part of the body; the head and such parts of the

prothorax as may be subsequently discovered to exist being placed entirely

on the dorsum of the body. The mesothorax in all the winged Diptera forms

by far the larger portion of the thoracic mass, the prominent part of it,

that projects backwards to a greater or less extent over the base of the

abdomen, being the scutellum. The first or prothoracic stigma is remarkably

large and distinct, and is by some called mesothoracic. Another large

stigma is placed very near to the halter (or balancer); the metathorax

being very small. An imperfect stigma is said by Lowne to exist in the

blowfly near the base of the wing. The number of abdominal segments

externally visible is very diverse; there may be as many as nine (in the

male _Tipula_), or as few as five, or even four, when the basal segment is

much concealed; the diminution is due to certain segments at the extremity

being indrawn and serving as a sort of tubular ovipositor in the female, or

curled under the body and altered in form in the other sex, so as to

constitute what is called a "hypopygium." In the female of Tipulidae the

body is terminated by some horny pieces forming an external ovipositor. In

nearly all Diptera the feet are five-jointed; the claws are well developed,

there being placed under each of them a free pad or membrane, the

"pulvillus"; there may be also a median structure between each pair of

claws, of diverse form, the "empodium."

On the surface of the body of many flies there will be seen an armature of

pointed bristles; these flies are called "chaetophorous"; where no

regularly arranged system of such bristles exists the fly is

"eremochaetous." In some families the arrangement of these bristles is of

importance in classification, and a system of description has been drawn up

by Baron Osten Sacken: this branch of descriptive entomology is known as

chaetotaxy.[354]

The wings are of great importance in classifying Diptera; but

unfortunately, like the other parts, they have not received an exhaustive

anatomical study, and Dipterologists are not agreed as to the names that

should be applied to their parts.

{447}[Illustration: Fig. 215—Nervuration of Dipterous wing. A, Wing of a

Tipulid, according to Loew, who uses the following nomenclature: _a_,

costal nervure; _b_, mediastinal; _c_, subcostal; _d_, radial; _e_,

cubital; _f_, discoidal; _g_, postical; _h_, anal; _i_, axillar; _x_,

transverse, _y_, posterior transverse, nervure; 1, 2, mediastinal areas; 3,

subcostal; 4, cubital; 5, anterior basal; 6, posterior basal; 7, anal; 8,

posterior marginal; 9, discoidal. B, Wing of an Acalypterate Muscid

(_Ortalis_), according to Schiner, who uses the following nomenclature:

(nervures, small letters; cells, capital letters): _a_, transverse

shoulder; _b_, auxiliary; _c_ to _h_, first to sixth longitudinal; _i_,

middle transverse; _k_, posterior transverse; _l_, _m_, _n_, _o_, costa;

_p_, anterior basal transverse; _q_, posterior basal transverse; _r_,

rudiment of a fourth nervure; _s_, axillary incision: A, B, C, first,

second, and third costal cells; D, marginal; E, sub-marginal; F, G, H,

first, second, and third posterior; I, discal; K, L, M, first, second, and

third basal cells; N, anal angle; O, alula.]

We give below figures of two systems that have been used by eminent

Dipterologists for the description of the nervures and cells. The

comprehension of these features of the Dipterous wing will be facilitated

by noticing that the wing—being extended at right angles to the body—is

divided by the longitudinal nervures into two great fields, anterior and

posterior, with an interval between them: this interval is traversed only

by a short cross-vein (marked x in Fig. 215 A, and i in B). This cross-vein

may be placed near the base or nearer to the tip of the wing; it is of

importance because no nervure in front of the median area traversed by it

can correspond with a nervure placed behind it in another wing. The very

different nature of the nervuration in the two wings we have figured will

readily be appreciated by an inspection of the parts posterior to the

little cross-vein. On the hind margin of the wing, near the base, there is

often a more or less free lobe (Fig. 215, B, O) called the "alula": still

nearer to the base, or placed on the side of the body, may be seen one or

two other lobes, of which the one nearer the alula is called the "tegula,"

or (when a lobe behind it is also present) the "upper tegula," (the

"antitegula" of Osten Sacken); the other being the "lower tegula." These

two terms are erroneous, the word tegula being definitely applied to

another part of the Insect-body. In speaking of this structure in the

following pages, we have preferred to call it the {448}"squama."[355] Those

Muscidae in which the squama covers the halter like a hood are called

"calypterate." In Fig. 216, we represent these structures, and in the

explanation have mentioned the synonyms. The terms we think most applicable

to the three lobes are alula, antisquama, squama. The squama may be called

"calypter" when it covers the halter.

[Illustration: Fig. 216—Parts at the base of the wing in _Calliphora_. _a_,

Anal angle or lobe of the wing; _b_, alula; _c_, antisquama, squama alaris,

or antitegula; _d_, squama, squama thoracicalis, tegula, calypter, or

calyptron; _e_, posterior extremity (scutellum) of the mesothorax; _f_,

scutum of mesothorax.]

The halteres—commonly called balancers or poisers—are perhaps the most

characteristic of all the Dipterous structures, though they are absent in

most of the few wingless forms of the Order. Outside the Diptera similar

organs appear to exist only in male Coccidae. The pair of halteres is

placed on the metathorax, one on each of the pleural regions. They are

believed to be the homologues of the hind wings; Weinland states[356] that

certain canals existing in the interior of the halter correspond to

wing-nervures. The halter may be described as a small rod-like body with a

head like a pin, this terminal part being, however, rather variable in

form. We have already stated that in many Diptera the squama forms a hood,

the position of which leads to the belief that it is an important adjunct

to the halter. Although the exact functions of the halteres are far from

clear, it is certain that they are highly complex bodies, of extremely

delicate structure: they are doubtless sense-organs, possessing as they do,

groups of papillae on the exterior and a chordotonal organ (a structure for

assisting the perception of sound) in the basal part; each halter is

provided with four muscles at the base, and can, like the wings, execute

most rapid vibrations. Seeing that they are the homologues of wings, it is

a remarkable fact that in no Diptera are they replaced by wings, or by

structures intermediate between these two kinds of organs.

INTERNAL STRUCTURE.—Information about the internal anatomy {449}is by no

means extensive. The tracheal system is highly developed, and has air-sacs

connected with it; a large pair at the base of the abdomen being called

aërostats by Dufour. Inside the thoracic spiracles there are peculiar

structures supposed by some to be voice-organs, while the abdominal

spiracles are said to be remarkably simple in structure. Lowne says that

there are ten or eleven pairs of spiracles in the Blow-fly; one of these,

near the base of the wing, is peculiar in structure, and may not be a true

stigma; he calls it a tympanic spiracle; it seems doubtful whether there

are more than seven abdominal pairs. The alimentary canal is very elongate,

and is provided with a diverticulum, the crop; this is usually called the

sucking stomach, though its function is extremely doubtful. The Malpighian

tubes are four in number, and are very elongate; in several groups of

Nemocera there are, however, five Malpighian tubes, a number known to occur

in only very few other Insects. The nervous system is remarkable on account

of the concentration of ganglia in the thorax, so as to form a thoracic, in

addition to the usual cephalic, brain. For particulars as to the positions

of the ganglia and the great changes that occur in the lifetime, the

student should refer to Brandt, to Künckel, and to Brauer.[357] Much

information as to the internal anatomy of the Blowfly is given by Lowne,

but it is doubtful to what extent it is applicable to Diptera in

general.[358]

[Illustration: Fig. 217—Acephalous larva or maggot of the blow-fly, with

the head, _a_, extended. (After Lowne.)]

The LARVAE of Diptera are—so far as the unaided eye is concerned—without

exception destitute of any kind of adornment, the vast majority of them

being of the kind known as maggots. None of them have true thoracic legs;

though in the earlier groups, pseudopods or protuberances of the body that

serve as aids in locomotion are common. Unlike what occurs in other Orders

the arrangement of these pseudopods on the body differs greatly in various

forms; in a few cases they are surmounted by {450}curved hairs. The most

important distinction in external form in Dipterous larvae is that while

those that are thorough maggots possess no visible head, others have a

well-marked one (Fig. 225); these are therefore called "eucephalous": they

have a mouth of the mandibulate type. In some other Dipterous larvae the

head is more or less reduced in size, and in the acephalous forms there is

only a framework of a few chitinous rods to represent it. The nervous

system in the most completely headless larvae is very remarkable, all the

ganglia being concentrated in a single mass placed in the thorax. The

tracheal system exhibits a great variety; some larvae have stigmata

arranged along the sides of the body after the fashion normal in

Insect-larvae; these are called "peripneustic"; as many as ten pairs of

stigmata may be present in these cases, but nine pairs is much more common.

Other larvae have a pair of stigmata placed at the termination of the body,

and another pair near the anterior extremity, the two pairs communicating

by large tracheal trunks extending the length of the body; these larvae are

said to be "amphipneustic": this is the condition usual in the more

completely acephalous larvae. Others have only the terminal pair of

spiracles, and are styled "metapneustic." Some begin life in the

metapneustic state and afterwards become amphipneustic. In the aquatic

larva of _Corethra_ there are no spiracles, though there is an imperfect

tracheal system. Many Dipterous larvae that live in water or in conditions

that prevent access of air to the body have remarkable arrangements for

keeping the tip of the body in communication with the atmosphere. The

stigmata in metapneustic and amphipneustic larvae are very remarkable

compound structures, exhibiting however great diversity; their

peculiarities and uses are not well understood; it appears very doubtful

whether some of them have any external opening. Reference may be made, as

to the variety of structure, to Meijere's paper[359] from which we take the

accompanying figure of a posterior stigmatic apparatus in _Lipara lucens_.

It appears that there is a compound chamber—"Filzkammer"—terminating

externally in lobes or fingers—"Knospen" and appearing as marks on the

outer surface: this chamber is seated on a tracheal tube, and is, Meijere

thinks, probably a secondary growth of the trachea coming to the outer

surface. It is traversed by what may be {451}considered the original

tracheal tube, opening externally as an external stigmatic

scar—"Stigmennarbe"—and with a second or inner scar placed internally. We

may conclude from what is already known that these structures will be found

to differ in the same larva according to the stage of its development.

[Illustration: Fig. 218—The posterior stigma of the larva of _Lipara

lucens_. _a_, One of the three "Knospen" or lobes; _b_, external stigmatic

scar; _c_, internal scar; _d_, stigmatic chamber (Filzkammer); _e_,

trachea. (After Meijere.)]

An extremely valuable summary of the characters and variety of Dipterous

larvae has been given by Brauer,[360] from which it appears that the larvae

of the first half of the family exhibit great variety and have been much

studied, while the more purely maggot-like forms of the Muscidae have, with

one or two exceptions, been little investigated.