This great series of beetles includes something like 35,000 species. It

approaches, like all the other series, the Polymorpha, especially the

family Erotylidae placed therein, but in the great majority of cases there

is no difficulty in recognising its members. The tarsi have never the

Heteromerous formula, the head is not constructed like that of

Rhynchophora, nor the mouth and feet like those of Adephaga; the antennae

are different from those of the Lamellicorns. The tarsi are really

five-jointed, for careful inspection shows that the long claw-joint has at

its extreme base a small nodule, which is undoubtedly the fourth joint

(Fig. 142, B). In speaking of the joints it is, however, customary not to

refer to this small and functionally useless joint at all, and to call the

claw-joint the fourth; when the little joint is referred to it may be

called the true fourth joint.

Nearly the whole of the enormous number of species of this series are

directly dependent on the vegetable kingdom for their nutriment; they are

therefore well styled Phytophaga. This term is, however, restricted by some

systematists to the family we have called Chrysomelidae. Although there is

enormous variety in this series, three families only can be at all

naturally distinguished, and this with difficulty. Of these the Bruchidae

are seed-feeders, the Chrysomelidae, as a rule, leaf-feeders, the

Cerambycidae wood and stem-feeders. The number of exceptions to this rule

is but small, though certain Cerambycidae and certain Chrysomelidae live on

roots.

FAM. 77. BRUCHIDAE.—_Prosternum extremely short; in front perpendicular;

behind the coxae, forming merely a transverse lamina with pointed

extremity. Hind femora more or less {277}thickened._ This comparatively

small family includes about 700 species of small, unattractive beetles. The

larvae live in seeds; hence some of the species are liable to be

transported by means of commerce; some of them do considerable injury; peas

and beans being specially subject to their attacks. They are able to

complete their growth with a very small amount of nutriment, some of them

consuming only a portion a little larger than themselves of a bean or pea.

The larvae are fat maggots without legs, but Riley has discovered that the

young larvae of _Bruchus pisi_ and _B. fabae_ have, when first hatched,

three pairs of legs which are subsequently lost. They also have peculiar

spinous processes on the pronotum. Both of these characteristics may be

correlative with the transient differences in the activities of the larva,

for the little creature is not at first located in the pea, but mines a

gallery in the pod, in which it moves about, subsequently entering the pea

and losing its legs. There is a good deal of difference in these respects

between the two species—_B. pisi_ and _B. fabae_—examined by Riley, and as

but little is known of the life-histories of other Bruchidae it is probable

that still greater variety prevails. Heeger has found that _Bruchus lentis_

sometimes requires two seeds to enable it to complete its growth; it is,

notwithstanding its legless state when half-grown, able to migrate by

dropping to the earth, and dragging itself along by its mandibles till it

comes to another pod into which it bites its way.

[Illustration: Fig. 141—_Bruchus pisi_ or pea-weevil. A, Young larva; B,

prothoracic spinous process; C, post-embryonic leg, greatly magnified; D,

pea-pod, with tracks of entry; E, portion of pod, with egg, and the

subsequently formed track, magnified; F, imago. (After Riley.)]

The family has, until recently, been placed in the {278}Rhynchophorous

series, with which it has, however, no direct connection. On the other

hand, it is so closely connected with Chrysomelidae that it is not possible

to indicate good characters to distinguish the two at present. The

Australian genus _Carpophagus_, and the large South American species of

_Caryoborus_ appear to be quite indistinguishable as families, though

Lacordaire and Chapuis placed one in Bruchidae, the other in Chrysomelidae.

The definition we have given applies, therefore, to the majority of the

family, but not to the aberrant forms just mentioned. The European genus

_Urodon_ appears to belong to Anthribidae, not to Bruchidae. The family

Bruchidae is called Mylabridae by some.

FAM. 78. CHRYSOMELIDAE.—_Antennae moderately long; eyes moderately large,

usually not at all surrounding the insertion of the antennae; upper surface

usually bare, frequently brightly coloured and shining._ This enormous

family comprises about 18,000 species of beetles, in which the form and

details of structure are very varied. No satisfactory character for

distinguishing Chrysomelidae from Cerambycidae has yet been discovered,

although the two families are certainly distinct and natural. Most of the

Chrysomelidae live on foliage; few of them are more than half an inch long,

whereas the Cerambycidae are wood-feeders and usually of more elongate form

and larger size. The potato beetle, or Colorado beetle, that occasioned so

much destruction in North America some thirty years ago, and the

introduction of which into Europe was anticipated with much dread, is a

good example of the Chrysomelidae. The turnip flea, a tiny hopping beetle,

is among the smallest forms of the family, and is a member of another very

extensive subdivision of Chrysomelidae, viz. Halticides. The term

Phytophaga is by many naturalists limited to Chrysomelidae, the

Cerambycidae being excluded. The classification of the family is but little

advanced, but the enormous number of species of Chrysomelidae are placed in

four divisions, viz.:—

[Illustration: Fig. 142—_Doryphora decemlineata_, the potato beetle. North

America. A, Imago; B, hind-tarsus. 3, third joint; 4, true fourth joint; 5,

so-called fourth joint.]

{279}Prothorax much narrower at the base than the elytra, and usually

without side-margins (raised edges). Sub-fam. 1. Eupoda; with three

divisions, Sagrides, Donaciides, Criocerides.

The basal ventral plates of the abdominal segments are somewhat shorter

in the middle than at the sides, the fourth one being often invisible in

the middle, while the fifth is very large. Sub-fam. 2. Camptosomes; with

six divisions, Megascelides, Megalopides, Clythrides, Cryptocephalides,

Chlamydes, Sphaerocarides.

In the other two groups there is no great disparity between the fourth

and fifth ventral plates.

Prothorax not greatly narrower at the base than the elytra, and usually

with distinct edges at the outsides. Sub-fam. 3. Cyclica; with four

divisions, Lamprosomides, Eumolpides, Chrysomelides, Galerucides.

Front of the head bent downwards or inflexed, so that the mouth is on the

lower aspect. Antennae inserted close together on the most anterior part

of the head, so that they are more forward than the mouth. Sub-fam. 4.

Cryptostomes; with two divisions Hispides, Cassidides.

In the other three divisions the mouth is placed as usual, but the

insertion of the antennae varies a good deal.

The larvae of about 100 species of the family are known; they are arranged

in accordance with their habits, by Chapuis,[145] in six groups, viz.:

1. Elongate larvae, living under water, and there undergoing their

metamorphosis. (Donaciides.)

2. Larvae mining in leaves, and undergoing their metamorphosis in the

leaf. (Hispides and some Halticides.)

3. Short convex larvae, frequently with leathery and pigmented

integuments, living exposed on plants. (Most of the Cyclica.)

4. Larvae of short form; covering the body with excrementitious matter.

(Some Criocerides.)

5. Peculiar larvae of short form, spiny, and protecting their bodies by

excrementitious matter attached by a special apparatus, the excrement

itself being modified so as to be suitable for retention. (Cassidides.)

6. Elongate, pallid, larvae with curved abdomen; living in shell-like

cases, and undergoing metamorphosis therein. (Most of the Camptosomes,

the habits of which are known.)

Though our knowledge of these larvae extends to only about 100 out of

18,000 species, the above category by no means includes all the kinds of

larvae; Captain Xambeu having recently discovered that the larva of

_Chrysochus pretiosus_ lives in the earth feeding on roots after the manner

of a _Rhizotrogus_ larva, which it resembles. The larva of _Sagra

splendida_ lives {280}inside the stems of _Dioscorea batatas_, in

swellings; the group Sagrides, to which it belongs, is a very anomalous

one.

i. Eupoda. The beetles of the genus _Donacia_ are of special interest. They

form, with the genus _Haemonia_, a peculiar group, well represented in

Europe, and also in our own country. They are all connected with aquatic

plants, the species of _Haemonia_ living entirely under water, while the

_Donacia_ live in the imago-state an aërial life, though many of them enter

the water with great readiness, and, it is said, are able to take wing from

the surface. The larvae live on the roots of aquatic plants, and derive not

only nutriment but air therefrom; they pass several months as pupae (or as

resting larvae waiting for pupation), under water in cocoons which they

construct, and which, incredible as it may seem, are filled with air, not

water. Exact details as to the construction of these cocoons are wanting.

It was formerly absurdly supposed that the larva swelled itself out to the

size of the cocoon it was about to make, and so served as a mould,

subsequently contracting. The observations of Schmidt-Schwedt[146] make it,

however, more probable that the plant itself furnishes the air which, under

pressure of the water (so he supposes), fills the cocoon; the larva wounds

the root, piercing to an air-vessel and then constructs the cocoon on this

spot, leaving to the last moment an orifice, according to Schmidt, as an

exit for the water. The larva uses a similar artifice for obtaining air; it

has no gills, but is provided near the extremity of the body with two sharp

chitinous processes which it drives into the root of the plant till it

penetrates an air-vessel. Schmidt thinks the processes serve as conduits to

conduct the air to the tracheae, but Dewitz thinks the air enters the larva

in a more normal manner, by means of a stigma placed at the base of the

piercing process. A similar larva exists in _Haemonia_; which genus is

additionally interesting from the fact that the imago lives entirely

submerged. It is not known how it breathes. This genus is the only member

of the Chrysomelidae that does not possess the structure of the feet that

is characteristic of the Phytophaga. The late Professor Babington about

sixty years ago found _H. curtisi_ at Cley on the Norfolk coast on

submerged _Potamogeton pectinatus_, but it has not been met with there for

a great many years.

The larvae of Criocerides are of two kinds, in one of which the {281}body

is peculiarly shaped in conformity with the curious habit of using the

excrement as a covering. The larva is less elongate than usual, and has the

anus placed on the upper surface, and formed so that the excrement when

voided is pushed forward on to the Insect; here it is retained by means of

a slimy matter, and a thick coat entirely covering the creature, is

ultimately formed. The larva of _Lema melanopa_ is not uncommon about

Cambridge, where it feeds on the leaves of growing corn. It is a remarkable

fact that even in one genus the species have some of them this habit, but

others not. The species of _Crioceris_ living on lilies—_C. merdigera_,

_e.g._—are noted for possessing it; while _C. asparagi_ does not protect

itself in this way, but emits fluid from its mouth when disturbed. This

larva is a serious nuisance in some localities to the cultivators of

asparagus. The eggs are deposited on the stems of the plant—as shown in our

figure—sometimes in great numbers.

The perfect Insects of many of the Criocerides possess a stridulating

organ. Two contiguous areas at the base of the last dorsal segment, where

they can be rubbed by the tips of the elytra, are slightly elevated and

bear very close and fine straight lines.

[Illustration: Fig. 143—_Crioceris asparagi._ A, Eggs in position on stem

of asparagus; B, one egg much enlarged; C, young larva. Cambridge.]

ii. The Camptosomes, as we have already noticed, are distinguished by a

peculiar structure of the abdomen. This character appears to be connected

with a very remarkable habit, viz. the formation of a case to envelop the

egg. The tip of the abdomen is somewhat curved downwards, and, in the

female, bears a hollow near the extremity; when an egg is extruded the

female holds it in this hollow by means of the hind legs, and envelops it

with a covering said to be excrementitious. When the larva hatches, it

remains within this case, and {282}subsequently enlarges it by additions

from its own body. The beautiful Insects of the genus _Cryptocephalus_,

which is fairly well represented in Britain, belong to this division. The

exotic group Megalopodes is incorrectly placed in Camptosomes; the side

pieces of the prothorax meet in it behind the middle coxae, as they do in

Rhynchophora. The species of Megalopodes stridulate by means of an area on

the base of the meso-scutellum rubbed by a ridge inside the pronotum, as in

the Cerambycidæ.

iii. The division Cyclica includes the great majority of Chryomelidae; we

have not less than 170 species in Britain. The larvae live, like those of

Lepidoptera, at the expense of foliage, and the species frequently multiply

to such an extent as to be injurious. Some of them are destroyed in great

numbers by Hymenopterous parasites, the Braconid genus _Perilitus_ being

one of the best known of these; in some cases the parasite deposits its

eggs in either the larva or perfect Insect of the beetle, and the

metamorphoses of the parasites in the latter case are sometimes, if not

usually, completed, the larvae emerging from the living beetles for

pupation.

iv. The Cryptostomes, though comparatively few in number of species,

include some very remarkable beetles. There are two groups, Hispides and

Cassidides. The former are almost peculiar to the tropics and are not

represented by any species in the British fauna. The head in this group is

not concealed; but in the Cassidides the margins of the upper surface are

more or less expanded, so that the head is usually completely hidden by the

expansion of the pronotum. Both the groups are characterised by the

antennae being inserted very near together, and by the short claw-joint of

the feet. _Hispa_ is one of the most extensive of the numerous genera of

Hispides, and is remarkable from the imago being covered on the surface

with long, sharp spines. But little is known as to the metamorphosis,

beyond the fact already alluded to, that the larvae of several species mine

the interior of leaves. The larva of _Hispa testacea_, according to

Perris,[147] makes use of the leaves of _Cistus salvifolius_ in Southern

Europe; it is broad and flat, and possessed of six short legs. The eggs are

not deposited by the parents inside the leaves, but are probably attached

to various parts of the plant. After hatching, the young larva enters a

leaf, and feeds on the parenchyma without rupturing {283}the epidermis; but

when it has consumed about three-fourths of the soft interior of the leaf

it ruptures the epidermis of the upper surface, and seeks another leaf;

this found, it places itself on the midrib, tears the upper epidermis, and

lodges itself in the leaf. In the case of this second leaf it attacks the

parenchyma in the neighbourhood of the petiole, and so forms an irregular

tube which has an open mouth, the point of entry. In this tube it undergoes

its metamorphosis. Each larva, it is said, always makes use of two leaves,

and of two opposed leaves. A knowledge of the habits of some of the larger

of the exotic Hispides would be of much interest.

[Illustration: Fig. 144—Pupa of Cassidid beetle (? _Aspidomorpha_ sp.). A,

With appendage extended; B, with the appendage reposing on the back. New

Britain.]

The Cassidides, in addition to the curious marginal expansion of their

upper surface, have the power of withdrawing the head into the thorax, and

hence they are often called shield or tortoise-beetles. They exhibit

considerable variety in form and colour, and some of them display a

peculiar metallic reflection of great delicacy and beauty; this disappears

entirely after death, but it may be restored by thoroughly moistening the

dead Insect. The colour, therefore, probably depends on the presence of

water in the integument. The larvae of Cassidides are notorious on account

of their habit of covering their bodies with dried excrement, for which

purpose they are provided with a forked {284}process at the posterior

extremity; this serves to place the protecting matter in a proper position

and to retain it there. The excrement assumes in various species forms so

peculiar that they cannot be considered merely incidental. In several

species this covering-matter is like lichen. This is the case with

_Dolichotoma palmarum_, the larva of which has, in place of the usual fork,

a more complex appendage on the back for the purpose of preparing and

retaining its peculiar costume. The pupae, too, sometimes retain the larval

skin. An extremely remarkable pupa of a Cassidid—possibly of the genus

_Aspidomorpha_—was recently found by Dr. Arthur Willey in New Britain (Fig.

144). The back of the pupa is covered with a complex appendage, so that the

creature has no resemblance to an Insect; this appendage is perhaps capable

of being moved, or even extended (Fig. 144, A), during life. Whether it may

be formed by the retention of portions of the moulted skins of the larva we

cannot say with certainty.

[Illustration: Fig. 145—Nest of intestinally-made filaments under which the

larva of _Porphyraspis tristis_ lives.]

The most remarkable of the Cassidid coverings yet discovered are those

formed by certain small beetles of the tropical American genus

_Porphyraspis_. _P. tristis_ is apparently a common Insect at Bahia, where

it lives on a cocoa-palm. The larva is short and broad, and completely

covers itself with a very dense coat of fibres, each many times the length

of the body, and elaborately curved so as to form a round nest under which

the larva lives. On examination it is found that these long threads are all

attached to the anal extremity of the Insect, and there seems no

alternative to believing that each thread is formed by small pieces of

fibre that have passed through the alimentary canal, and are subsequently

stuck together, end to end. The process of forming these long fibres, each

one from scores of pieces of excrement, and giving them the appropriate

curve, is truly remarkable. The fibres nearest to the body of the larva are

abruptly curled so as to fit exactly, and make an even surface; but the

outside fibres stand out in a somewhat bushy fashion. The construction is

much like that of a tiny bird's nest. Señor Lacerda informed the writer

that the larva makes a nest as soon as it is hatched. Another

_Porphyraspis_—_P. palmarum_—has been recorded as {285}forming similar

nests on a species of _Thrinax_ in St. Domingo. Candèze says[148] that when

it has completed its growth the larva ejects on to the leaf a quantity of

semi-liquid matter, and this, on drying, sticks the nest to the leaf, so

that the metamorphosis is effected under shelter.

FAM. 79. CERAMBYCIDAE (_Longicorns_).—_Form usually oblong, not much curved

in outline at the sides; surface very frequently rendered dull by a very

minute hairiness, which often forms a pattern; antennae usually long, and

their insertion much embraced by the eyes._ This great family of beetles

includes some 12,000 or 13,000 known species. The elegance and variety of

their forms and the charm of their colours have caused them to attract much

attention, so that it is probable that a larger proportion of the existing

species have been obtained than is the case in any other of the great

families of Coleoptera. Still it is not likely that one-half of the living

forms are known. It is not possible at present to point out any one

character of importance to distinguish Cerambycidae from Chrysomelidae,

though the members of the two families have, as a rule, but little

resemblance in external appearance. Most of them live on, or in, wood,

though many are nourished in the stems of herbaceous plants. The larvae

live a life of concealment, and are soft, whitish grubs with powerful

mandibles, and usually with a comparatively small head, which is not much

exserted from the thorax. Most of them are without legs, but a good many

have three pairs of small legs, and there are numerous cases in which the

surface of the body is furnished above or below with swellings believed to

act as pseudopods (Fig. 84), and help the larvae to move about in their

galleries; but this is probably not the sole function of these organs, as

their surface is varied in character, and often not of a kind that appears

specially adapted to assist in locomotion. There is a slight general

resemblance between the larvae of Cerambycidae and those of Buprestidae,

and when the thorax of a Longicorn larva is unusually broad, _e.g._

_Astynomus_, this similarity is very pronounced.

[Illustration: Fig. 146—_Saperda populnea._ Britain.]

{286}The modes of life of Cerambycid larvae exhibit considerable variety,

and much perfection of instinct is displayed by the larvae, as well as by

the mother beetles. The larvae of _Saperda populnea_, are common in certain

woods in the South of England in the stems of aspen; they consume only a

small quantity of the interior of the stem, and are probably nourished by

an afflux of sap to the spot where they are situated. _Elaphidion villosum_

is called the oak-pruner in North America. The parent beetle lays an egg

near the axilla of a leaf-stalk or small stem, and the young larva enters

this and feeds on the tender material; as it grows it enters a larger limb,

and makes an incision within this in such a manner that the wood falls to

the ground with the larva within it, the dead wood serving subsequently as

pabulum and as a shelter, within which the metamorphosis is completed. The

species of the American genus _Oncideres_ are called girdlers, because the

parent beetle, after laying an egg in a small branch, girdles this round

with a deep incision, so that the portion containing the larva sooner or

later falls to the ground. The growth of a Longicorn larva frequently takes

more than a year, and under certain circumstances it may be enormously

prolonged. _Monohammus confusus_ has been known to issue from wooden

furniture in a dwelling-house when the furniture was fifteen years old.

Individuals of another Longicorn have issued from the wood of a table,

twenty and even twenty-eight years after the felling of the tree from which

the furniture was made. Sereno Watson has related a case from which it

appears probable that the life of a Longicorn beetle extended over at least

forty-five years.[149] It is generally assumed that the prolongation of

life in these cases is due to the beetle resting quiescent for long after

it has completed the metamorphosis. Recent knowledge, however, renders it

more probable that it is the larval life that is prolonged; the larva

continuing to feed, but gaining little or no nutriment from the dry wood in

these unnatural conditions. Mr. C. O. Waterhouse had for some years a

Longicorn larva under observation, feeding in this way in the wood of a

boot-tree;[150] the burrows in the wood contained a great deal of minute

dust indicating that the larva passed much matter through the alimentary

canal, probably with little result in the way of nutriment.

{287}There are numerous Longicorns that bear a great resemblance in form

and colour to Insects to which they are not related. Haensch[151] has

noticed that species of the genus _Odontocera_ resemble various

Hymenoptera, one species being called _O. braconoides_; he also observed

that these Hymenoptera-like Longicorns, instead of withdrawing their

underwings under the elytra as beetles generally do, vibrate them rapidly

like Hymenoptera. A large number of Longicorns stridulate loudly by rubbing

a ridge inside the pronotum on a highly specialised, striate surface at the

base of the scutellum, and therefore covered up when the Insect is

contracted in repose. A few produce noise by rubbing the hind femora

against the edges of the elytra, somewhat after the fashion of

grasshoppers. In this case there appears to be comparatively little

speciality of structure, the femora bearing, however, more or less distinct

small granules. The species of the Hawaiian genus _Plagithmysus_ produce

sound in both these manners, the thoracic stridulating organ being

beautifully developed, while in some species the margin of the elytra and

base of the femora are also well adapted for the purpose of

sound-production, and in a few species of the genus there are also

highly-developed stridulating surfaces on the hind and middle coxae. This

is the only case in which a beetle is known to possess more than one set of

sound-organs in the imago state.

Three divisions of this family are distinguished, viz.—

1. Front coxae large and transverse; prothorax with distinct side

margins. Sub-fam. 1. Prionides.

2. Front coxae not greatly extended transversely, thorax not margined;

last joint of maxillary palpus not pointed, usually broader (more or

less) than the preceding joint. Sub-fam. 2. Cerambycides.

3. Front coxae usually round and deeply embedded; last joint of maxillary

palpus pointed; front tibiae with a more or less distinct, slanting

groove on the inner side. Sub-fam. 3. Lamiides.

The Prionides are on the average considerably larger in size than the

members of the other divisions, and they include some of the largest of

Insects. The Amazonian _Titanus giganteus_ and the Fijian _Macrotoma heros_

are amongst the most gigantic. Some of the Prionides have a great

development of the mandibles in the male sex analogous to that we have

already noticed in Lucanidae. The larvae of the large Prionides appear in

various parts of the world to have been a favourite food with native

{288}tribes, and Lumholz states that they are really good eating. In

consequence of the destruction of forests that has progressed so largely of

late years these gigantic Prionides have become much rarer.

Several aberrant forms are included in Prionides. The genus _Parandra_ has

five-jointed tarsi; the third joint being much smaller than usual, so that

the fourth joint is not concealed by it. The Brazilian _Hypocephalus

armatus_ was for long a subject of dispute as to its natural position, and

was placed by different authorities in widely-separated families of

Coleoptera. The structure of this aberrant Longicorn seems to be only

explicable on the hypothesis of warfare amongst the males.[152] Nothing is,

however, known as to the habits and history of the Insect, and only one or

two specimens of the female have yet been obtained.

The family Spondylidae has been proposed for some of these aberrant

Longicorns, but as it includes but very few, and highly discrepant,

species, it is neither natural nor of much use for systematic purposes.

The Lamiides are the most highly specialised division of the Longicorns,

and includes the larger number of the species. The front of the head is

usually placed at right angles to the vertex, and in some cases (groups

Hippopsini, Spalacopsini) it is strongly inflexed, so that the mouth is

placed on the under side of the head. The extension of the eyes round the

antennae is accompanied by very curious shapes of those organs, and not

infrequently each eye is divided into two more or less widely-separated

parts, so that the Insect has, on the external surface, four eyes.

SERIES VI. RHYNCHOPHORA.

_Head more or less prolonged in front to form a snout or beak, called

rostrum. Tarsi four-jointed, usually at least the third joint broad and

densely pubescent beneath._

This enormous series includes about 25,000 species, and as may well be

imagined shows a great variety of structure amongst its forms. The vast

majority may, however, be readily recognised by the two characters

mentioned above. There are some cases in which the beak is indistinct, and

others in which the tarsi are {289}five-jointed (_Dryophthorus_), and even

slender (Platypides). In these cases a close examination shows that the

gular region on the middle of the back of the under surface of the head

cannot be detected, and that the back of the prosternum is very strongly

consolidated by the side-pieces of the thorax meeting together and being

very firmly joined behind the coxae. The beak is in the great majority

perfectly distinct, though it varies so extremely in form that it can only

be briefly described by saying that it is a prolongation of the head in

front of the eyes, or that the antennae are inserted on its sides near to,

or far from, the tip. It has been ascertained in many cases that the

rostrum is used by the female to assist in placing the eggs in suitable

places, a hole being bored with it; in some cases it is also used to push

the egg far into the hole in which it has previously been placed by the

ovipositor; but there are many forms in which it is fairly certain that it

is not so used. What purpose it serves in the male is totally unknown. In

many members of the series, the rostrum differs in form in the two sexes,

and in most, if not in all, these cases it is clear that the distinctions

tend in the direction of making the beak of the female more efficient for

the mechanical purpose we have mentioned.

[Illustration: Fig. 147.—_Eugnoristus monachus_ ♀. Madagascar. A, The

imago; B, front of pronotum, head, and rostrum.]

It was proposed by Leconte and Horn to separate this series from all the

other Coleoptera as a primary division, and they looked on it as of lower

or more imperfect structure. Packard has very properly protested against

this interpretation; and there seems to be no reason whatever for

considering the Rhynchophora as "lower" than other beetles; indeed we

should be inclined to place such forms as Calandrides {290}amongst the most

perfect of Insects; their external structure (as shown by _Eugnoristus

monachus_, Fig. 147) being truly admirable.

Only four families of Rhynchophora can be at present accepted as

satisfactory; one of these—Curculionidae—includes an enormous majority of

the whole series. Though it is probable that it will ultimately be divided

into several families, the attempts to that end that have already been made

are not satisfactory.

FAM. 80. ANTHRIBIDAE.—_Palpi usually not covered, but distinct and

flexible. Antennae often long, not elbowed, the first joint not very long.

Third joint of tarsus small, usually much concealed by being embraced by

the second joint. Pygidium exposed; propygidium deeply grooved in the

middle._ This family includes 800 or more species, which are mostly

tropical; it is very sparsely represented in the faunas of Europe and North

America. It is quite distinct from Curculionidae with which it was formerly

associated. It contains many graceful Insects having a certain resemblance

with Longicorns on account of the large development of the antennae. The

habits and metamorphoses are but little known. It seems probable that many

species find their nutriment in old wood or boleti The larvae of some

genera (_Cratoparis_ and _Araeocerus_) have legs, but in others the legs

are wanting, and the larvae are said to completely resemble those of

Curculionidae. In the larva of our tiny British species, _Choragus

sheppardi_, the legs are replaced by three pairs of thoracic, sac-like

pseudopods. This Insect makes burrows in dead branches of hawthorn. The

larvae of the genus _Brachytarsus_ have been ascertained to prey on

Coccidae.

[Illustration: Fig. 148—_Platyrhinus latirostris_, Anthribidae. Britain. A,

the perfect Insect; B, tarsus and tip of tibia.]

FAM. 81. CURCULIONIDAE (Weevils).—_The beak of very variable length and

thickness; the palpi small, nearly always concealed within the mouth,

short, and rigid. Labrum absent. Antennae of the majority elbowed,_ i.e.

_with the basal joint longer, and so formed that when it is laterally

extended the other joints can be placed in a forward direction._ This

enormous family includes {291}about 20,000 known species, and yet a large

portion of the species yearly brought from the tropics still prove to be

new. The rostrum or beak exhibits excessive variety in form, and is in many

cases different in the sexes; in this case it is usually longer and thinner

in the female. As the rostrum is one of the chief characters by which a

member of the family may be recognised, it is necessary to inform the

student that in certain forms (the Australian Amycterides, _e.g._) the

organ in question may be so short and thick that it is almost absent. In

these cases the Insect may be identified as a Curculionid by the gular area

being absent on the under side of the head, and by the concealment of the

palpi. The tarsi are usually of the same nature as those of Phytophaga,

already described, but the true fourth joint is less visible. In the

Brachycerides this joint is not present, and the third joint is not lobed.

The palpi are flexible and more or less exserted in a very few species

(Rhynchitides); in Rhinomacerides there is also present a minute labrum.

The front coxae are deeply embedded, and in many forms the prosternum is

peculiar in structure; the side-pieces (epimera) meeting at the back of the

prosternum in the middle line. This, however, is not universal in the

family, and it occurs in some other beetles (_e.g._, Megalopodides of the

Phytophaga). The larvae are without legs. They are vegetarian, the eggs

being deposited by the mother-beetle in the midst of the food. These larvae

may be distinguished from those of Longicorns by the general form, which is

sub-cylindric or rather convex, not flattened, and more particularly by the

free, exserted head, the mouth being directed downwards; the attitude is

generally a curve, and the anterior part of the body is a little the

thicker. No part of plants is exempt from the attacks of the larvae of

Curculionidae; buds, twigs, leaves, flowers, fruits, bark, pith, roots and

galls may each be the special food of some Curculionid. Certain species of

the sub-families Rhynchitides and Attelabides prepare leaves in an

elaborate manner to serve as food and dwelling for their young. If young

birches, or birch bushes from 5 to 10 feet in height, be looked at in the

summer, one may often notice that some of the leaves are rolled so as to

form, each one, a little funnel. This is the work of _Rhynchites_ (or

_Deporaus_) _betulae_, a little Curculionid beetle (Fig. 149). An

inspection of one of these funnels will show that it is very skilfully

constructed.

{292}[Illustration: Fig. 149.—The leaf-rolling of _Rhynchites betulae_.

Britain. A, Female beetle, magnified; B, the beetle forming the first

incision on a leaf; C, the completed roll. (B and C after Debey.)]

The whole of a leaf is not used in the formation of a funnel, cuts being

made across the leaf in suitable directions. The beetle standing on a leaf,

as shown in the figure, proceeds to cut with its mandibles an incision

shaped like an erect S, commencing at a certain part of the circumference,

and ending at the midrib of the leaf; the beetle then goes to the other

side of the midrib, and continues its incision so as to form another S-like

curve considerably different from the first; being prostrate and less

abrupt. Thus the blade of the leaf is divided into two halves by certain

curved incisions, the midrib remaining intact. The little funnel-twister

now commences to roll up the leaf to form the funnel; and this part of the

work is greatly facilitated by the shape of the incisions. Going back to

the spot where it commenced work, by the aid of its legs it rolls one side

of the leaf round an ideal axis, somewhat on the same plan as that adopted

by a grocer in forming a paper-funnel for sugar. The incisions are found to

be just of the right shape to make the overlaps in the rolling, and to

retain them rolled-up with the least tendency to spring back. After some

other operations destined to facilitate subsequent parts of its task, the

beetle enters the rolled-up part of the leaf and brings it more perfectly

together; it again comes out and, pursuing a different system, holds on

with the legs of one side of the body {293}to the roll, and with the other

legs drags to it the portion of the leaf on the other side of the midrib so

as to wrap this part (_i.e._ the result of its second incision) round the

part of the funnel already constructed. This being done the Insect again

enters the funnel, bites three or four small cavities on the inside of the

leafy wall and deposits an egg in each. Afterwards it emerges and fits the

overlaps together in a more perfect manner so as to somewhat contract the

funnel and make it firmer; then proceeding to the tip, this is operated on

by another series of engineering processes and made to close the orifice;

this part of the operation being analogous to the closing by the grocer of

his paper-funnel after the sugar has been put in. The operation of the

beetle is, however, much more complex, for it actually makes a sort of

second small funnel of the tip of the leaf, bends this in, and retains it

by tucking in some little projections. The work, which has probably lasted

about an hour, being now completed, the creature takes a longer or shorter

rest before commencing another funnel. We have given only a sketch of the

chief points of the work, omitting reference to smaller artifices of the

craft master; but we may remark that the curved incisions made by the

beetle have been examined by mathematicians and duly extolled as being

conducted on highly satisfactory mathematical principles. It is impossible

at present for us to form any conception as to the beetle's conceptions in

carrying out this complex set of operations. Our perplexity is increased if

we recollect its life-history, for we then see that neither precept or

example can have initiated its proceedings, and that imitation is out of

the question. The eggs hatch in their dark place, giving rise to an eyeless

maggot, which ultimately leaves the funnel for the earth. The parts of this

maggot subsequently undergo complete change to produce the motionless pupa

of entirely different form, from which emerges the perfect Insect. Hence

the beetle cannot be considered to have ever seen a funnel, and certainly

has never witnessed the construction of one, though, when disclosed, it

almost immediately sets to work to make funnels on the complex and perfect

system we have so imperfectly described. More general considerations only

add to the perplexity we must feel when reflecting on this subject. Why

does the Insect construct the funnel at all? As a matter of protection it

appears to be of little use, for the larvae are known to suffer from the

attacks {294}of parasites as other Insects do. We have not the least reason

for supposing that this mode of life for a larva is, so far as utility is

concerned, better than a more simple and usual one. Indeed, extraordinary

as this may appear, it is well known that other species of the same genus

adopt a simple mode of life, laying their eggs in young fruits or buds. We

think it possible, however, that a knowledge of the mode of feeding of this

larva may show that a more perfect nutrition is obtained from a

well-constructed cylinder, and if so this would to a slight extent satisfy

our longing for explanation, though throwing no light whatever on the

physiology or psychology of the artificer, and leaving us hopelessly

perplexed as to why a beetle in ages long gone by should or could adopt a

mode of life that by long processes of evolution should, after enormous

difficulties have been overcome, attain the perfection we admire.[153]

FAM. 82. SCOLYTIDAE.—_Rostrum extremely short, broad; tibiae frequently

denticulate externally; antennae short, with a broad club._ This family is

not at all sharply distinguished from certain groups of Curculionidae (from

Cossonides _e.g._), but as the species have somewhat different habits, and

in the majority of cases can be readily distinguished, it is an advantage

to separate the two families. About 1400 species are at present known. Most

of them are wood- and bark-feeders; some bore into hard wood; a few mine in

twigs or small branches of trees, but the majority live in the inner layers

of the bark; and this also serves as the nidus of the larvae. A small

number of species have been found to inhabit the stems of herbaceous

plants, or to live in dry fruits. Owing to their retiring habits they are

rarely seen except by those who seek them in their abodes, when they may

often be found in great profusion. The mother-beetle bores into the

suitable layer of the bark, forming a sort of tunnel and depositing eggs

therein. The young larvae start each one a tunnel of its own, diverging

from the parent tunnel; hence each batch of larvae produces a system of

tunnels, starting from the parents' burrow, and in many species these

burrows are {295}characteristic in form and direction, so that the work of

particular Scolytids can be recognised by the initiated.

The Platypides bore into the wood of trees and stumps; they are chiefly

exotic, and little is known about them. They are the most aberrant of all

Rhynchophora, the head being remarkably short, flat in front, with the

mouth placed on the under surface of the head, there being no trace of a

rostrum: the tarsi are elongate and slender, the third joint not being at

all lobed, while the true fourth joint is visible. Hence they have not the

appearance of Rhynchophora. Some authorities treat the Platypides as a

distinct family.

Some of the members of the group Tomicides also bore into the wood. Recent

observations have shown that there is an important feature in the economy

of certain of these wood-borers, inasmuch as they live gregariously in the

burrow, and feed on peculiar fungi that develop there, and are called

ambrosia. According to Hubbard[154], some species cultivate these fungi,

making elaborate preparations to start their growth. The fungi, however,

sometimes increase to such an extent as to seal up the burrows, and kill

the Insects by suffocation.

Scolytidae sometimes multiply to an enormous extent, attacking and

destroying the trees in wooded regions. Much discussion has taken place as

to whether or not they are really injurious. It is contended by one set of

partisans that they attack only timber that is in an unhealthy, dying, or

dead condition. It may be admitted that this is usually the case; yet when

they occur in enormous numbers they may attack timber that is in a sort of

neutral state of health, and so diminish its vigour, and finally cause its

destruction. Hence it is of great importance that they should be watched by

competent foresters.

The larvae of Scolytidae are said to completely resemble those of

Curculionidae: except in the group Platypides, where the body is straight

and almost cylindrical, and terminates in an oblique truncation bearing a

short hard spine.[155]

FAM. 83. BRENTHIDAE.—_Form elongate; rostrum straight, directly continuing

the long axis of the body, often so thick as to form an elongate head;

antennae not elbowed._ The Brenthidae form a family of about 800 species,

remarkable for the excessive {296}length and slenderness of some of its

forms, and for the extreme difference in the sexes that frequently exists.

It is well represented in the tropics only, and very little is known as to

the natural history and development. These beetles are stated to be

wood-feeders, and no doubt this is correct in the case of the majority of

the species; but Mr. Lewis observed in Japan that _Zemioses celtis_ and

_Cyphagogus segnipes_ are predaceous, and enter the burrows of wood-boring

Insects to search for larvae as prey: they are very much modified in

structure to permit this; and as the other members of the group

Taphroderides are similar in structure, it is probable that they are all

predaceous. Nothing whatever is known as to the larval history of these

carnivorous forms. Indeed an uncertainty, almost complete, prevails as to

the early stages of this family. Riley has given a sketch of a larva which

he had no doubt was that of _Eupsalis minuta_, the North American

representative of the family; if he is correct the larva differs from those

of Curculionidae by its elongate form, and by the possession of thoracic

legs: these, though small, are three-jointed. Descriptions, supposed to be

those of Brenthid larvae, were formerly published by Harris and

Motschoulsky; but it is now clear that both were mistaken.

[Illustration: Fig. 150—_Eupsalis minuta_. North America. A, Larva; B,

pupa; C, female imago; D, head of male. (After Riley.)]

In the higher forms of Brenthidae the rostrum of the female is perfectly

cylindrical and polished, and the mandibles are minute, hard, pointed

processes placed at its tip. This organ is admirably adapted to its

purpose; it being used for boring a hole in wood or bark, in which an egg

is subsequently deposited. The males in these cases are extremely

different, so that considerable curiosity is felt as to why this should be

so. In some cases their head is thick, and there may be no rostrum, while

large powerful mandibles are present.

In other cases the rostrum is slender, but of enormous length, so that it

may surpass in this respect the rest of {297}the body, although this itself

is so drawn out as to be quite exceptional in the Insect world:[156] the

antennae are inserted near the tip of the rostrum instead of near its base,

as they are in the female. The size of the males is in these cases usually

much larger than that of the female.[157] The males of some species fight;

they do not, however, wound their opponent, but merely frighten him away.

In _Eupsalis_ it appears that the rostrum of the female is apt to become

fixed in the wood during her boring operations; and the male then

extricates her by pressing his heavy prosternum against the tip of her

abdomen; the stout forelegs of the female serve as a fulcrum and her long

body as a lever, so that the effort of the male, exerted at one extremity

of the body of the female, produces the required result at the other end of

her body. The New Zealand Brenthid, _Lasiorhynchus barbicornis_, exhibits

sexual disparity in an extreme degree: the length of the male is usually

nearly twice that of the female, and his rostrum is enormous. It is at

present impossible to assign any reason for this; observations made at the

request of the writer by Mr. Helms some years ago, elicited the information

that the female is indefatigable in her boring efforts, and that the huge

male stands near by as a witness, apparently of the most apathetic kind.

COLEOPTERA OF UNCERTAIN POSITION.

There are three small groups that it is impossible at present to place in

any of the great series of beetles.

FAM. 84. AGLYCYDERIDAE.—_Tarsi three-jointed, the second joint lobed; head

not prolonged to form a beak._ The two most important features of

Rhynchophora are absent in these Insects, while the other structural

characters are very imperfectly known, many parts of the external skeleton

being so completely fused that the details of structure are difficult of

appreciation. Westwood considered the tarsi to be really four-jointed, but

it is not {298}at all clear that the minute knot he considered the third

joint is more than the articulation of the elongate terminal joint. The

family consists only of two or three species of _Aglycyderes_, one of which

occurs in the Canary Islands, and one or two in New Zealand and New

Caledonia. The former is believed to live in the stems of _Euphorbia

canariensis_; a New Zealand species has been found in connection with the

tree-ferna. _Cyathea dealbata_

[Illustration: Fig. 151—_Aglycyderes setifer_. Canary Islands. A, Imago; B,

tarsus according to Westwood; C, according to nature; D, maxilla; E,

labium.]

FAM. 85. PROTERHINIDAE.—_Tarsi three-jointed, the second joint lobed; head

of the male scarcely prolonged, but that of the female forming a definite

rostrum; maxillae and ligula entirely covered by the mentum._ As in the

preceding family the sutures on the under side of the head and prosternum

cannot be detected. The minute palpi are entirely enclosed in the buccal

cavity. There is a very minute true third joint of the tarsus, at the base

of the terminal joint, concealed between the lobes of the second joint. The

family consists of the genus _Proterhinus_; it is confined to the Hawaiian

Islands, where these Insects live on dead wood in the native forests. The

genus is numerous in species and individuals.

[Illustration: Fig. 152—_Proterhinus lecontei_. Hawaiian Islands. A, Male;

B, female; C, front foot, more magnified.]

STREPSIPTERA (or RHIPIPTERA, Stylopidae).—_Male small or minute; prothorax

extremely small; mesothorax moderate, the elytra reduced to small, free

slips; metathorax and wings very large; nervuration of the latter

radiating, without cross nervules. Female a mere sac, with one extremity

smaller and forming a sort of neck or head._

{299}[Illustration: Fig. 153.—Sexes of Strepsiptera. A, Male of _Stylops

dalii_ (after Curtis); B, female of _Xenos rossii_ (after von Siebold).]

These curious Insects are parasitic in the interior of other Insects, of

the Orders Hymenoptera and Hemiptera. Their structure and their

life-histories entitle them to be ranked as the most abnormal of all

Insects, and entomologists are not agreed as to whether they are aberrant

Coleoptera or a distinct Order. The newly-hatched larva is a minute

triungulin (Fig. 154), somewhat like that of _Meloe_; it fixes itself to

the skin of the larva of a Hymenopterous Insect, penetrates into the

interior, and there undergoes its metamorphoses, the male emerging to enjoy

a brief period of an abnormally active, indeed agitated, existence, while

the female never moves. It is important to note that these Strepsiptera do

not, like most other internal parasites, produce the death of their hosts;

these complete their metamorphosis, and the development of the parasite

goes on simultaneously with that of the host, so that the imago of the

Strepsipteron is found only in the imago of the host.[158] After the young

_Stylops_ has entered its host it feeds for a week or so on the fat-body

(apparently by a process of suction), then moults and assumes the condition

of a footless maggot, in which state it remains till growth is completed.

At the latter part of this period the history diverges according to sex;

the female undergoes only a slight metamorphic development of certain

parts, accompanied apparently by actual degradation of other parts; while

the male goes on to pupation, as is normal in Insects. (We may remark that

the great features of the development of the sexes are parallel with those

of Coccidae in Hemiptera.) When the Hymenopterous larva changes to a pupa,

the larva of the Strepsipteron pushes one extremity of its body between two

of the abdominal rings of its host, so that this extremity becomes

external, and in this position it completes its metamorphosis, the

{300}male emerging very soon after the host has become an active winged

Insect, while the female undergoes no further change of position, but

becomes a sac, in the interior of which young develop in enormous numbers,

finally emerging from the mother-sac in the form of the little triungulins

we have already mentioned. This is all that can be given at present as a

general account; many points of the natural history are still obscure,

others have been merely guessed; while some appear to differ greatly in the

different forms. A few brief remarks as to these points must suffice.

Bees carrying, or that have carried, Strepsiptera, are said to be

stylopised (it being a species of the genus _Stylops_ that chiefly infests

bees); the term is also used with a wider application, all Insects that

carry a Strepsipterous parasite being termed stylopised, though it may be a

Strepsipteron of a genus very different from _Stylops_ that attacks them.

The development of one or more Strepsiptera in an Insect usually causes

some deformity in the abdomen of its host, and effects considerable changes

in the condition of its internal organs, and also in some of the external

characters. Great difference of opinion prevails as to what these changes

are; it is clear, however, that they vary much according to the species,

and also according to the extent of the stylopisation. Usually only one

_Stylops_ is developed in a bee; but two, three, and even four have been

observed:[159] and in the case of the wasp, _Polistes_, Hubbard has

observed that a single individual may bear eight or ten individuals of its

Strepsipteron (_Xenos_, n. sp.?).

[Illustration: Fig. 154—Young larva of _Stylops_ on a bee's-hair. Greatly

magnified. (After Newport.)]

There is no exact information as to how the young triungulins find their

way to the bee-larvae they live in. Here again the discrepancy of opinion

that prevails is probably due to great {301}difference really existing as

to the method. When a _Stylops_ carried by an Insect (a Hymenopteron, be it

noted, for we have no information whatever as to Hemiptera) produces young,

they cover the body of the host as if it were powdered, being excessively

minute and their numbers very great; many hundreds, if not thousands, of

young being produced by a single _Stylops_. The species of the wasp genus

_Polistes_ are specially subject to the attacks of _Stylops_; they are

social Insects, and a stylopised specimen being sickly does not as a rule

leave the nest; in this case the _Stylops_ larva may therefore have but

little difficulty in finding its way to a Hymenopterous larva, for even

though it may have to live for months before it has the chance of attaching

itself to a nest-building female, yet it is clearly in the right

neighbourhood. The bee genus _Andrena_ has, however, quite different

habits; normally a single female makes her nest underground; but in the

case of a stylopised female it is certain that no nest is built, and no

larvae produced by a stylopised example, so that the young triungulins must

leave the body of the bee in order to come near their prey. They can be

active, and have great powers of leaping, so that it is perhaps in this way

possible for them to attach themselves to a healthy female bee.

[Illustration: Fig. 155.—Portion of early stages of _Xenos rossii_. (After

von Siebold.) A, Small male larva; B, small female larva; C, full-grown

male larva; D, full-grown female larva; E, the so-called "cephalothorax"

and adjacent segment of adult female. (The newly-hatched larva is very much

like that of _Stylops_ shown in Fig. 154.)]

We have still only very imperfect knowledge as to the structure and

development of Strepsiptera. Indeed but little information has been

obtained since 1843.[160] Before that time the mature female was supposed

to be a larva, and the triungulins found in it to be parasites. Although

the erroneous character of these views has been made clear, the problems

that have been suggested present great difficulties. Apparently the change

from the triungulin condition (Fig. 154) to the parasitic larvae (Fig. 155,

A, B) is extremely great and abrupt, and it appears also that during

{302}the larval growth considerable sexual differentiation occurs (Fig.

155, C, D); details are, however, wanting, and there exists but little

information as to the later stages. Hence it is scarcely a matter for

surprise that authorities differ as to which is the head and which the anal

extremity of the adult female. Von Siebold apparently entertained no doubt

as to the part of the female that is extruded being the anterior extremity;

indeed he called it a cephalothorax. Supposing this view to be correct, we

are met by the extraordinary facts that the female extrudes the head for

copulatory purposes, that the genital orifice is placed thereon, and that

the young escape by it. Meinert[161] contends that the so-called

cephalothorax of the adult is the anal extremity, and that fertilisation

and the escape of the young are effected by the natural passages, the

anterior parts of the body being affected by a complete degeneration.

Nassonoff, in controversion of Meinert, has recently pointed out that the

"cephalothorax" of the young is shown by the nervous system to be the

anterior extremity. It still remains, however, to be shewn that the

"cephalothorax" of the adult female corresponds with that of the young, and

we shall not be surprised if Meinert prove to be correct. The internal

anatomy and the processes of oogenesis appear to be of a very unusual

character, but their details are far from clear. Brandt has given some

particulars as to the nervous system; though he does not say whether taken

from the male or female, we may presume it to be from the former; there is

a supra-oesophageal ganglion, and near it a large mass which consists of

two parts, the anterior representing the sub-oesophageal and the first

thoracic ganglia, while the posterior represents two of the thoracic and

most of the abdominal ganglia of other Insects; at the posterior extremity,

connected with the other ganglia by a very long and slender commissure,

there is another abdominal ganglion.[162]

It is a matter of great difficulty to procure material for the prosecution

of this study; the fact that the instars to be observed exist only in the

interior of a few Hymenopterous larvae, which in the case of the bee,

_Andrena_, are concealed under ground; and in the case of the wasps,

_Polistes_, placed in cells in a nest of wasps, adds greatly to the

difficulty. It is therefore of interest to know that Strepsiptera occur in

Insects with incomplete {303}metamorphosis. They have been observed in

several species of Homoptera; and the writer has a large Pentatomid bug of

the genus _Callidea_, which bears a female Strepsipteron apparently of

large size. This bug[163] is abundant and widely distributed in Eastern

Asia, and it may prove comparatively easy to keep stylopised examples under

observation. Both v. Siebold and Nassonoff think parthenogenesis occurs in

Strepsiptera, but there appear to be no facts to warrant this supposition.

Von Siebold speaks of the phenomena of Strepsipterous reproduction as

paedogenesis, or pseudo-paedogenesis, but we must agree with Meinert that

they cannot be so classed.

The males of Strepsiptera live for only a very short time, and are very

difficult of observation. According to Hubbard the males of _Xenos_ dash

about so rapidly that the eye cannot see them, and they create great

agitation amongst the wasps in the colonies of which they are bred.

Apparently they are produced in great numbers, and their life consists of

only fifteen or twenty minutes of fiery energy. The males of _Stylops_ are

not exposed to such dangers as those of _Xenos_, and apparently live

somewhat longer—a day or two, and even three days are on record. The

individuals of _Andrena_ parasitised by _Stylops_ are apparently greatly

affected in their economy and appear earlier in the season than other

individuals; this perhaps may be a reason, coupled with their short lives,

for their being comparatively rarely met with by entomologists.

[Illustration: Fig. 156.—Abdomen of a wasp (_Polistes hebraeus_) with a

Strepsipteron (_Xenos_ ♀) in position, one of the dorsal plates of the

wasp's abdomen being removed. _a_, Projection of part of the parasite; _b_,

line indicating the position of the removed dorsal plate.]

It is not possible at present to form a valid opinion as to whether

Stylopidae are a division of Coleoptera or a separate Order. Von Siebold

considered them a distinct Order, and Nassonoff, who has recently discussed

the question, is also of that opinion.

{304}CHAPTER VI

LEPIDOPTERA—OR BUTTERFLIES AND MOTHS

ORDER VI. LEPIDOPTERA.

_Wings four; body and wings covered with scales usually variegate in

colour, and on the body frequently more or less like hair: nervures

moderate in number, at the periphery of one wing not exceeding fifteen,

but little irregular; cross-nervules not more than four, there being

usually only one or two closed cells on each wing, occasionally none.

Imago with mouth incapable of biting, usually forming a long coiled

proboscis capable of protrusion. Metamorphosis great and abrupt; the

wings developed inside the body; the larva with large or moderate head

and strong mandibles. Pupa with the appendages usually adpressed and

cemented to the body so that it presents a more or less even, horny

exterior, occasionally varied by projections that are not the appendages

and that may make the form very irregular: in many of the smaller forms

the appendages are only imperfectly cemented to the body._

Lepidoptera, or butterflies and moths, are so far as ornament is concerned

the highest of the Insect world. In respect of intelligence the Order is

inferior to the Hymenoptera, in the mechanical adaptation of the parts of

the body it is inferior to Coleoptera, and in perfection of metamorphosis

it is second to Diptera. The mouth of Lepidoptera is quite peculiar; the

proboscis—the part of the apparatus for the prehension of food—is

anatomically very different from the proboscis of the other Insects that

suck, and finds its nearest analogue in the extreme elongation of the

maxillae of certain Coleoptera, e.g. _Nemognatha_. {305}The female has no

gonapophyses, though in certain exceptional forms of Tineidae, there are

modifications of structure connected with the terminal segments, that have

as yet been only imperfectly investigated. As a rule, the egg is simply

deposited on some living vegetable and fastened thereto. Lepidoptera are

the most exclusively vegetarian of all the Orders of Insects; a certain

number of their larvae prey on Insects that are themselves filled with

vegetable juices (Coccidae, Aphidae) and a very small number (_Tinea_,

etc.) eat animal matter. In general the nutriment appears to be drawn

exclusively from the fluids of the vegetables, the solid matter passing

from the alimentary canal in large quantity in the form of little pellets

usually dry, and called frass. Hence the quantity of food ingested is

large, and when the individuals unduly increase in number, forest trees

over large areas are sometimes completely defoliated by the caterpillars.

[Illustration: Fig. 157.—Metamorphosis of a Lepidopteron (_Rhegmatophila

alpina_, Notodontidae). (After Poujade, _Ann. Soc. ent. France_, 1891.)

Europe. A, Egg; B, young larva, about to moult; C, adult larva; D, head and

first body-segment of adult larva, magnified; E, pupa, × 2/1; F, male moth

in repose; G, female moth in repose.]

Lepidoptera pass a larger portion of their lives in the pupal stage than

most other Insects do; frequently during nine months of the year the

Lepidopteron may be a pupa. In other Orders of {306}Insects it would appear

that the tendency of the higher forms is to shorten the pupal period, and

when much time has to be passed between the end of the feeding up of the

larva and the appearance of the imago, to pass this time as much as

possible in the form of a resting-larva, and as little as may be in the

form of a pupa; in Lepidoptera the reverse is the case; the resting-larva

period being usually reduced to a day or two. Hence we can understand the

importance of a hard skin to the pupa. There are, however, numerous

Lepidopterous pupae where the skin does not attain the condition of

hardness that is secured for the higher forms by the chitinous exudation we

have mentioned; and there are also cases where there is a prolonged

resting-larva period: for instance _Galleria mellonella_ spins a cocoon in

the autumn and remains in it as a resting larva all the winter, becoming a

pupa only in the spring. In many of these cases the resting-larva is

protected by a cocoon. It is probable that the chief advantage of the

perfect chitinous exudation of the Lepidopterous pupa is to prevent the

tiny, complex organisation from the effects of undue transpiration.

Bataillon has suggested that the relation of the fluid contents of the pupa

to air and moisture are of great importance in the physiology of

metamorphosis.

The duration of life is very different in various forms of Lepidoptera. It

is known that certain species (_Ephestia kuehniella_, _e.g._) may go

through at least five generations a year. On the other hand, certain

species that feed on wood or roots may take three years to complete their

life-history; and it is probable that some of the forms of Hepialidae are

even longer lived than this.

Lepidoptera have always been a favourite Order with entomologists, but no

good list of the species has ever been made, and it would be a difficult

matter to say how many species are at present known, but it can scarcely be

less than 50,000. In Britain we have about 2000 species.

The close affinity of the Order with Trichoptera has long been recognised:

Réaumur considered the latter to be practically Lepidoptera with aquatic

habits, and Speyer pointed out the existence of very numerous points of

similarity between the two. Brauer emphasised the existence of mandibles in

the nymph of Trichoptera as an important distinction: the pupa {307}of

_Micropteryx_ (Fig. 211) has however been recently shown to be similar to

that of Trichoptera, so that unless it should be decided to transfer

_Micropteryx_ to Trichoptera, and then define Lepidoptera and Trichoptera

as distinguished by the condition of the pupa, it would appear to be very

difficult to retain the two groups as distinct.

STRUCTURE OF IMAGO.—The head of a Lepidopteron is in large part made up of

the compound eyes; in addition to these it frequently bears at the top a

pair of small, simple eyes so much concealed by the scales as to cause us

to wonder if seeing be carried on by them. The larger part of the front of

the head is formed by the clypeus, which is separated by a well-marked line

from the epicranium, the antennae being inserted on the latter near its

point of junction with the former. There is sometimes (_Saturnia_,

_Castnia_) on each side of the clypeus a deep pocket projecting into the

head-cavity. The other parts of the head are but small. The occipital

foramen is very large.[164]

[Illustration: Fig. 158—External structure of a female butterfly, _Anosia

plexippus_. (After Scudder.) _a_, Base of antenna; _b_, pronotum; _b^2_,

scutum of mesothorax; _c_, clypeus; _cx_, coxa; _d_, scutellum; _d^1_,

scutellum of metathorax; _e_, post-scutellum (= base of phragma); _em_,

epimeron; _ep_, episternum; _f_, scutum of metathorax; _m_, basal part of

proboscis (= maxilla); _o_, eye; _p_, labial palp; _r_, mesosternum; _s_,

prothoracic spiracle; _t_, tegula; _tr_, trochanter; 1-9, dorsal plates of

abdomen.]

The antennae are always conspicuous, and are very various in form; they are

composed of numerous segments, and in the males of many species attain a

very complex structure, especially in Bombyces and Psychidae; they

doubtless function in such cases as sense-organs for the discovery of the

female.

The largest and most important of the mouth-parts are the maxillae and the

labial palpi, the other parts being so small as to render their detection

difficult. The labrum is a very short, {308}comparatively broad piece,

visible on the front edge of the clypeus; its lateral part usually forms a

prominence which has often been mistaken for a mandible; Kellogg has

applied the term "pilifer" to this part. In the middle of the labrum a

small angular or tongue-like projection is seen just over the middle of the

base of the proboscis; this little piece is considered by several

authorities to be an epipharynx.

[Illustration: Fig. 159—Mouth of Lepidoptera. Tiger-moth, _Arctia caja_. A,

Seen from front; B, from front and below, _a_, Clypeus; _b_, labrum; _c_,

epipharynx; _d_, mandibular area; _d′_, prominence beneath mandibular area;

_e_, one side of haustellum or proboscis; _f_, maxillary palp; _g_, labial

palp.]

MANDIBLES.—Savigny, Westwood, and others considered the parts of the labrum

recently designated pilifers by Kellogg to be the rudimentary mandibles,

but Walter has shown that this is not the case.[165] The mandibles are

usually indistinguishable, though they, or some prominence possibly

connected with them,[166] may frequently be detected in the neighbourhood

of the pilifers; they are, according to Walter, largest and most perfectly

developed in _Eriocephala_, a genus that was not distinguished by him from

_Micropteryx_ and was therefore termed "niedere Micropteryginen," _i.e._

lower Micropteryges. The opinion entertained by Walter that _Micropteryx_

proper (his "höhere Micropteryginen") also possesses rudimentary mandibles

is considered by Dr. Chapman, no doubt with reason, to be erroneous.[167]

The mandibles, however, in the vast majority of Lepidoptera can scarcely be

said to exist at all in the imago; there being only an obtuse

projection—without trace of {309}articulation—on each side of the labrum;

and even this projection is usually absent. Meinert recognised these

projections as mandibles in _Smerinthus populi_, and Kellogg in _Protoparce

carolina_, another large Sphinx moth. They appear to be unusually well

developed in that group. In _Castnia_ they are even more definite than they

are in Sphingidae.

The MAXILLAE are chiefly devoted to the formation of the proboscis. Their

basal portions are anatomically very indefinite, though they exist very

intimately connected with the labium. Each usually bears a small tubercle

or a segmented process, the representative of the maxillary palpus. The

proboscis itself consists of the terminal, or outer, parts of the two

maxillae, which parts are closely and beautifully coadapted to form the

spirally coiled organ, that is sometimes, though incorrectly, called the

tongue. The exact morphology of the Lepidopterous proboscis has not been

established. The condition existing in the curious family Prodoxidae (see

p. 432), where a proboscis coexists with another structure called a

maxillary tentacle, suggests a correspondence between the latter and the

galea of a typical maxilla; and between the proboscis and the lacinia or

inner lobe of a maxilla: but J. B. Smith is of opinion that the tentacle in

question is a prolongation of the stipes. The condition of the parts in

this anomalous family (Prodoxidae) has not, however, been thoroughly

investigated, and Packard takes a different view of the proboscis; he

considers that "it is the two galeae which become elongated, united and

highly specialised to form the so-called tongue or glossa of all

Lepidoptera above the Eriocephalidae."[168] The proboscis in some cases

becomes very remarkable, and in certain Sphingidae is said to attain, when

unrolled, a length of ten inches. In some cases the maxillary lobes do not

form a proboscis, but exist as delicate structures, pendulous from the

mouth, without coadaptation (_Zeuzera aesculi_, the Wood-leopard moth). In

other forms they are absent altogether (_Cossus_, _e.g._), and in

_Hepialus_ we have failed to detect any evidence of the existence of the

maxillae. On the other hand, in _Micropteryx_ the maxillae are much more

like those of a mandibulate Insect; and various other Microlepidoptera

approach more or less a similar condition. In the genus last mentioned

{310}the maxillary palpi are largely developed, flexible and slender.

According to Walter various forms of palpus intermediate between that of

_Micropteryx_ and the condition of rudimentary tubercle may be found

amongst the Microlepidoptera.[169]

LABIUM.—The labial palpi are usually largely developed, though but little

flexible; they form conspicuous processes densely covered with scales or

hairs, and curve forwards or upwards, rarely downwards, from the under side

of the head, somewhat in the fashion of tusks. The other parts of the

labium are frequently represented merely by a membranous structure, united

with the maxillae and obstructing the cavity of the pharynx. Where the

proboscis is absent it is difficult to find any orifice leading to the

alimentary canal, such opening as may exist being concealed by the

overhanging clypeus and labium. In some forms, _Saturnia_, _e.g._, there

appears to be no buccal orifice whatever. In _Hepialus_ the labium is in a

very unusual condition; it projects externally in the position usually

occupied by the labial palpi, these organs being themselves extremely

short. It is very difficult to form an opinion as to the structure of the

labium and other mouth-parts when the maxillae are not developed, as in

these cases the parts are of a delicate membranous nature, and shrivel

after death. This is the explanation of the fact that in descriptive works

we find vague terms in use such as "mouth aborted" or "tongue absent."

The mouth of the Lepidopterous imago is a paradoxical structure; it differs

very greatly from that of the larva, the changes during metamorphosis being

extreme. We should thus be led to infer that it is of great importance to

the creatures; but, on the other hand, the various structures that make up

the mouth, as we have remarked, are frequently absent or reduced to

insignificant proportions; and even in forms where the apparatus is highly

developed the individuals seem to be able to accomplish oviposition without

taking food, or after taking only very minute quantities. It is therefore

difficult to understand why so great a change should occur during the

metamorphosis of the Insects of this Order. It has been ascertained that in

some forms where the mouth is atrophied the stomach is in a correlative

condition; but we are not aware that any investigations have been made as

to whether this correspondence is general or exceptional.

{311}The exact mode in which the proboscis acts is in several respects

still obscure, the views of Burmeister and Newport being in some points

erroneous. Towards the tip of the proboscis there are some minute but

complex structures considered by Fritz Müller to be sense-organs, and by

Breitenbach to be mechanical instruments for irritating or lacerating the

delicate tissues of blossoms. It is probable that Müller's view will prove

to be correct. Nevertheless the proboscis has considerable power of

penetration; there being a moth, "_Ophideres fullonica_" that causes

considerable damage to crops of oranges by inserting its trunk through the

peel so as to suck the juices.[170] The canal formed by each maxilla opens

into a cavity inside the front part of the head. This cavity, according to

Burgess,[171] is a sort of sac connected with five muscles, and by the aid

of this apparatus the act of suction is performed: the diverticulum of the

alimentary canal, usually called a sucking-stomach, not really possessing

the function formerly attributed to it.

The PROTHORAX is very small, being reduced to a collar, between the head

and the alitrunk, of just sufficient size to bear the front pair of legs.

Its most remarkable feature is a pair of processes, frequently existing on

the upper surface, called "patagia." These in many cases (especially in

Noctuidae) are lobes capable of considerable movement, being attached only

by a narrow base. In _Hepialus_, on the contrary, they are not free, but

are merely indicated by curved marks on the dorsum. The patagia are styled

by many writers "tegulae." They are of some interest in connection with the

question of wing-like appendages on the prothorax of Palaeozoic insects,

and they have been considered by some writers[172] to be the equivalents of

true wings. The Mesothorax is very large, especially its upper face, the

notum, which is more or less convex, and in the higher forms attains a

great extension from before backwards. The notum consists in greater part

of a large anterior piece, the meso-scutum, and a {312}smaller part, the

meso-scutellum behind. In front of the scutum there is a piece termed

prae-scutum by Burgess. It is usually small and concealed by the front part

of the scutum; but in _Hepialus_ it is large and horizontal in position. It

is of importance as being the chief point of articulation with the

prothorax. The scutellum is more or less irregularly rhomboidal in form;

its hinder margin usually looks as if it were a lobe or fold placed in

front of the base of the abdomen or metathorax, according to whether the

latter is concealed or visible. In some of the higher forms this

meso-scutellar lobe is prominent, and there may be seen under its

projection a piece that has been called the post-scutellum, and is really

the base of the great mesophragma, a chitinous piece that descends far down

into the interior of the body. In addition to the front pair of wings the

mesothorax bears on its upper surface another pair of appendages, the

tegulae: in the higher forms they are of large size; they are fastened on

the front of the mesothorax, and extend backwards over the joint of the

wing with the body, being densely covered with scales so that they are but

little conspicuous. These appendages are frequently erroneously called

patagia, but have also been called scapulae, pterygodes, paraptera, and

shoulder-tufts, or shoulder-lappets. The lower surface of the mesothorax is

much concealed by the large and prominent coxae, but the sternum and the

two pleural pieces on each side, episternum and epimeron, are easily

detected. The area for attachment of the anterior wing on each side is

considerable, and appears to be of rather complex structure; its anatomy

has been, however, but little studied.

The METATHORAX is small in comparison with the preceding segment, to which

it is intimately co-adapted, though the two are really connected only by

delicate membrane, and can consequently be separated with ease by

dissection. The metanotum consists of (1) the scutum, which usually appears

externally as an anterior piece on each side; (2) the scutellum, forming a

median piece placed behind the scutum, which it tends to separate into two

parts by its own extension forwards. In order to understand the structure

of the metathorax it is desirable to dissect it off from the larger

anterior segment, and it will then be found that its appearance when

undissected is deceptive, owing to its being greatly arched, or folded in

the {313}antero-posterior direction. A broad, but short phragma descends

from the hind margin of the metascutellum into the interior of the body. It

should be noted that though the metanotum is forced, as it were, backwards

by the great extension of the mesonotum in the middle line of the body, yet

at the sides the metanotum creeps forward so as to keep the points of

attachment of the hind wings near to those of the front wings. In many

forms of Hesperiidae, Sphingidae, Noctuidae, etc. the true structure of the

metanotum is further concealed by the back of the mesoscutellum reposing

on, and covering it.

Difference of opinion exists as to the thoracic Spiracles; there is one

conspicuous enough in the membrane behind the pronotum, and it is thought

by some writers that no other exists. Westwood and Scudder, however, speak

of a mesothoracic spiracle, and Dr. Chapman considers that one exists.

Minot describes[173] a structure behind the anterior wing, and thinks it

may be an imperfect spiracle, and we have found a similar stigma in

_Saturnia pavonia_. At the back of the thorax there is on each side in some

Lepidoptera (Noctuidae, _Arctia_, etc.), a curious large cavity formed by a

projection backwards from the sides of the metasternum, and a corresponding

development of the pleura of the first abdominal segment. Minot and others

have suggested that this may be an organ of hearing.

The ABDOMEN differs according to the sex. In the female seven segments are

conspicuous dorsally, but only six ventrally, because the first segment is

entirely membranous beneath, and is concealed between the second abdominal

ventral plate and the posterior coxae. Besides these segments there are at

the hind end two others smaller, more or less completely withdrawn into the

body, and in certain cases forming an ovipositor. These nine segments are

usually considered to constitute the abdomen; but according to

Peytoureau,[174] a tenth dorsal plate is represented on either side of the

anal orifice, though there is no trace of a corresponding ventral plate. In

the male the segments, externally conspicuous, are one more than in the

female. According to the authority quoted,[175] this sex has also truly ten

abdominal segments, the ninth segment being withdrawn to a greater or

{314}less extent to the inside of the body, and modified to form part of a

copulatory apparatus; its dorsal portion bears a process called the

"uncus"; the anal orifice opens on the inner face of this process, and

below it there is another process—developed to a greater or less

extent—called the "scaphium." The ventral portion of the ninth segment

bears a lobe, the "saccus" (Peytoureau, _l.c._). On each side of the ninth

abdominal segment there is a process called the "valve," the internal wall

of which bears some hook-like or other processes called "harpes"; it is

continued as a membrane surrounding the "oedeagus," or penis, and—bearing

more or less distinct prominences—connects with the scaphium. In many forms

the parts alluded to, other than the valves, are concealed by the latter,

which come together when closed, and may be covered externally with scales

like the rest of the abdomen. Peytoureau considers that the uncus is really

the dorsal plate of a tenth segment, and that the scaphium is the tenth

ventral plate. Thus, according to this view, the ninth segment is extensive

and complex, being very highly modified in all its parts: while the tenth

segment is greatly reduced. The structure of the male organs is simpler in

Lepidoptera, and less varied than it is in the other great Orders of

Insects. There are seven pairs of abdominal spiracles on the upper parts of

the membranous pleurae.

[Illustration: Fig. 160—_Acherontia atropos._ The termination of ♂ body,

one side removed. _IX_, Ninth dorsal plate; _IX’_, ninth ventral; _s_,

lobe, saccus, of ninth ventral plate; _X_, tenth dorsal plate, or uncus;

_sc_, scaphium, or tenth ventral plate; _a_, position of anus; _b_,

chitinised band of scaphium; _V_, valve or clasper; _c_, hooks, or harpes,

of clasper; _p_, penis (or oedeagus). (After Peytoureau.)]

LEGS.—The legs are long, slender, covered with scales, and chiefly

remarkable from the fact that the tibiae sometimes bear articulated spurs

on their middle as well as at the tip. The front tibia usually possesses on

its inner aspect a peculiar mobile pad; this seems to be in some cases a

combing organ; it also often acts as a cover to peculiar scales. The tarsi

are five-jointed, with two small claws and a small apparatus, {315}the

functional importance of which is unknown, between the claws.

WINGS.—The wings are the most remarkable feature of this Order; it is to

them that butterflies owe their beauty, the surfaces of the wings being

frequently adorned with colours and patterns of the most charming and

effective nature. These effects are due to minute scales that are implanted

in the wing-membrane in an overlapping manner, somewhat similar to the

arrangement of slates on the roof of a house. The scales are very readily

displaced, and have the appearance of a silky dust. We shall describe their

structure and allude to their development subsequently. The wings are

usually of large size in comparison with the Insect's body: in the genus

_Morpho_, the most gorgeous of the butterflies, they are enormous, though

the body is small; so that when deprived of these floats the Insect is

insignificant. The great expanse of wing is not correlative with great

powers of flight, though it is perhaps indicative of flying with little

exertion; for the small-winged Lepidoptera, Sphingidae, etc., have much

greater powers of aërial evolution than the large-winged forms. The area of

the wing is increased somewhat by the fact that the scales on the outer

margin, and on a part or on the whole of the inner margin, project beyond

the edges of the membrane that bears them: these projecting marginal scales

are called fringes. In many of the very small moths the actual size of the

wing-membranes is much reduced, but in such cases the fringes may be very

long, so as to form the larger part of the surface, especially of that of

the hind wings. Frequently the hind wings are of remarkable shape, being

prolonged into processes or tails, some of which are almost as remarkable

as those of _Nemoptera_ in the Order Neuroptera.

The wings are very rarely absent in Lepidoptera; this occurs only in the

female sex, no male Lepidopterous imago destitute of wings having been

discovered. Although but little is known of the physiology of flight of

Lepidoptera, yet it is clearly important that the two wings of the same

side should be perfectly coadapted or correlated. This is effected largely

by the front wing overlapping the hind one to a considerable extent, and by

the two contiguous surfaces being pressed, as it were, together. This is

the system found in butterflies and in some of the large moths, such as

Lasiocampidae and Saturniidae; in these cases the hind {316}wing always has

a large shoulder, or area, anterior to its point of insertion. In most

moths this shoulder is absent, but in its place there are one or more stiff

bristles projecting forwards and outwards, and passing under a little

membranous flap, or a tuft of thick scales on the under face of the front

wing; the bristle is called the "frenulum," the structure that retains it a

"retinaculum." In _Castnia_ (Fig. 162) and in some Sphingidae there is the

unusual condition of a highly-developed shoulder (_s_) coexisting with a

perfect frenulum (_f_) and retinaculum (_r_). The frenulum and retinaculum

usually differ in structure, and the retinaculum in position, in the two

sexes of the same moth; the male, which in moths has superior powers of

flight, having the better retaining organs. Hampson says "the form of the

frenulum is of great use in determining sex, as in the males of all the

forms that possess it, it consists of hairs firmly soldered together so as

to form a single bristle, whilst in nearly all females it consists of three

or more bristles which are shorter than that of the male; in one female

Cossid I have found as many as nine. Also in the large majority of moths

the retinaculum descends from the costal nervure in the male, while in the

female it ascends from the median nervure."[176] This sexual difference in

a structure for the discharge of a function common to the two sexes is a

very remarkable fact. There are a few—very few—moths in which the bases of

the hind wings are not well coadapted with the front wings, and do not

possess a frenulum, and these species possess a small more or less free

lobe at the base of the front wing that droops towards the hind wing, and

may thus help to keep up an imperfect connexion between the pair; this lobe

has been named a jugum by Professor Comstock. Occasionally there is a jugum

on the hind as well as on the front wing. There is usually a very great

difference between the front and the hind wings; for whereas in the front

wing the anterior portion is doubtless of great importance in the act of

flight and is provided with numerous veins, in the hind wing, on the other

hand, the corresponding part has not a similar function, being covered by

the front wing; hence the hind wing is provided with fewer nervures in the

anterior region, the divisions of the subcostal being less numerous than

they are in the front wing. In the moths possessing a jugum the two wings

differ but little from one {317}another, and it is probable that they

function almost as four separate wings instead of as two pairs.

WING-NERVURES.—The nervures or ribs of the wings are of great importance in

Lepidoptera, as at present they furnish the chief characters for

classification and for the discussions of phylogeny that are so numerous in

entomological literature. On looking at wings that have been deprived of

their scales it will be noticed (Fig. 161) that the ribs are much more

numerous at the outer margins than they are near the points of attachment

of the wings, and that there is usually but one cell (or area completely

enclosed by ribs). This latter point is one of the chief peculiarities of

the Lepidopterous wing; in Insect-wings generally the number of cells in

proportion to the area of the wings and to the number of nervures is

greater than it is in Lepidoptera, for in the latter there are few or no

cross-nervures. Hence there is sometimes no closed cell at all on the wing

(Fig. 161, II. B). The maximum number of closed cells is six; this is found

in some species of _Micropteryx_, while in _Hepialus_ there may be three or

four; but the rule is that there is only one cell in the Lepidopterous

wing. When the number of cells is increased this is not necessarily due to

an increase in the cross-nervures; and in fact it is generally due to

irregular forking or to the sinuous form of the longitudinal nervures

themselves (see wing of _Castnia_, Fig. 162, A.). Some authorities consider

that all transverse or cross-veins in Lepidoptera are merely portions of

longitudinal veins having diverted courses. When a portion of a nervure

beyond the basal or primary portion serves as a common piece to two forked

parts external to it, it is called a stalk (Fig. 162, A, _e_). There are

cases in which the furcation takes place in the opposite direction, so that

a nervure is double at the base of the wing (Fig. 161, I, A, 1_a_, and B,

1_b_). This important condition has not yet been adequately discussed.

{318}[Illustration: Fig. 161.—Wing-nervuration of Lepidoptera. I, Diagram

of moths' wings (after Hampson); II, of a butterfly's wings (_Morpho

menelaus_ ♂, after Staudinger and Schatz). A, front, B, hind wing. I.—_c_,

costal; _sc_, subcostal; _m_, median; 1_a_, 1_b_, 1_c_, internal nervures;

_f_, frenulum; 2, 3, 4, branches of median nervure; 5, lower radial; 6,

upper radial; 7-11, divisions of the subcostal; 12, termination of costal;

_c_, cell; _d_, discocellular nervure. II.—C, costal; SC, subcostal; M,

median; SM and SN, submedian nervures; 1A, inner-margin nervure; UR, lower

radial; OR, upper radial; SC^1 to SC^5, divisions of subcostal; M^1 to M^3,

divisions of median nervure; C, cell; DC, discocellulars.]

Turning to the mode of designation of the nervures,[177] we may commence by

remarking that no system satisfactory from a practical as well as from a

theoretical point of view has yet been devised. The diagrams given in

figure 161 will enable us to explain the methods actually in vogue; I.

representing the system, dating from the time of Herrich-Schaeffer, chiefly

used by British naturalists, and II. that adopted by Staudinger and Schatz

in their recent great work on the Butterflies of the world. The three

anterior nervures in both front and hind wings correspond fairly well, and

are called, looking at them where they commence at the base of the wing,

"costal," "subcostal," and "median" nervures. The nervures near the inner

margin of the wing (that is the lower part in our figures) differ much in

the front and hind wings, consisting either of two or of three separate

portions not joined even at the base. British entomologists call these

"branches or divisions of the internal nervure": the Germans call the more

anterior of them the "submedian," and the more internal the "inner-margin

nervure"; they are also frequently called anal nervures. The cross-nervure

that closes the cell is called discocellular; when apparently composed of

two or three {319}parts joined so as to form angles, the parts are called,

according to position, upper, lower, and middle discocellulars. One or more

short spurs may exist on the front part of the basal portion of the hind

wing; these are called praecostal. The branches or terminal divisions of

the nervures should be called nervules; they are usually mentioned by the

numbers shewn in the diagram (Fig. 161, I.). In addition to this, it is

only necessary to remember that number 2 is always assigned to the

posterior division of the median nervure, the nervules below this being all

called 1, and distinguished by the addition of _a_, _b_, _c_ when

requisite. This course is necessary, because if it were not adopted the

corresponding nervules on the front and hind wings would bear different

numbers.

The use of this system of numbers for the nervules is becoming general, and

it answers fairly well for practical purposes. On the other hand, extreme

discrepancy exists as to the nomenclature of the nervures and nervules, and

there are almost as many systems as there are authorities.

The normal number of nervules is, on the front wing, 11 + 1 or 2 inner

marginal, and on the hind wing 7 + 2 or 3 inner marginal. In the aberrant

moths of the genus _Castnia_ the nervuration is unusually complex and

irregular (Fig. 162), and an analogous condition occurs in our common

Goat-moth (_Cossus ligniperda_). In _Hepialus_ and _Micropteryx_ (the

jugate moths of Comstock) the hind wings are less dissimilar in nervuration

from the front wings than they are in other Lepidoptera.[178]

[Illustration: Fig. 162—Wing-nervuration of _Castnia_. Undersides of, A,

front, B, hind wings. 1_a_, 1_b_, 1_c_, 1_d_, Inner marginal nervures; 2,

lower branch of median; 8, subcostal of hind wing; 12, subcostal of front

wing; _e_, "stalk" of 8 and 9; _f_, frenulum; _r_, retinaculum; _s_,

shoulder; _g_, articulation of wing.]

INTERNAL ANATOMY.[179]—The alimentary canal extends as a long, {320}slender

oesophagus through the length of the thorax, dilating when it reaches the

abdomen to form a tubular stomach; before this it is somewhat enlarged to

form an indistinct crop, and gives off a large diverticulum usually called

a sucking stomach. According to Burgess, this structure does not possess

the function ascribed to it by this name, and he terms it a food-reservoir.

The Malpighian tubes are six in number, three on each side, and each set of

three unite to form a common tube opening into the posterior extremity of

the stomach; behind them the alimentary canal continues in the form of a

slender, tortuous intestine, expanding at the extremity of the body to form

a rectum. The dorsal or circulatory vessel commences near the posterior

extremity of the body, but in the front part of the abdomen is deflexed to

pass under the great phragma into the thorax, where it rises abruptly to

the dorsal wall, but is again abruptly deflexed, forming a loop, and is

then prolonged above the oesophagus into the head: at the summit of the

thoracic loop there may be a dilatation called the aortal chamber. The

supra- and infra-oesophageal ganglia are consolidated into a mass pierced

by the oesophagus: there is a minute frontal ganglion; the ventral chain

consists of three much approximated thoracic ganglia and four abdominal

ganglia separated from the thoracic by a long interval.

[Illustration: Fig. 163—Internal anatomy of Lepidoptera. Section of the

body of a female butterfly, _Anosia plexippus_. (After Scudder.) The

portion to the left of the vertical line more magnified. I. II. III.

thoracic segments; 1-9, abdominal segments; _a_, antenna; _a_, anus; _ac_,

aortal chamber; _ag^1_, etc., abdominal ganglia; _agl^1_, _agl^2_,

accessory glands; _ao_, aorta; _br_, brain; _c_, colon; _cp_, copulatory

pouch; _cx^1_, _cx^2_, _cx^3_, coxae; _fr_, food-reservoir; _g^1_,

suboesophageal ganglion; _h_, dorsal vessel; _i_, intestine; _lm_, area

filled by wing muscles; _l.or_, ovary, or egg-tubes of left side; _mv_,

Malpighian tube (the two others of the right side cut away, except small

portions); _mx_, maxilla; _o_, oviduct; _oo_, its orifice; _oe_,

oesophagus; _ov.c_, end of left ovary; _p_, labial palp; _ph_, pharynx;

_r.ov_, terminal parts of right ovarian tubes, turned to one side, after

the tubes have been cut away; _sd_, salivary duct; _sgl_, salivary gland;

_sp_, spermatheca; _st_, stomach; _tg_, thoracic ganglia; _v_, copulatory

orifice.]

{321}The male sexual organs consist of the two testes placed in a common

capsule, from which proceed a pair of contiguous vasa deferentia (dilated

soon after their origin to form the vesiculae seminales); into each vas

there opens a long, tubular gland; the two vasa subsequently unite to form

a long, coiled, ejaculatory duct. It is in the structure of the female

sexual organs that the most remarkable of the anatomical characters of

Lepidoptera is found, there being two external sexual orifices. The imago

has, in the great majority of cases, four egg-tubes in each ovary; the pair

of oviducts proceeding from them unite to form a single unpaired (azygos)

oviduct which terminates by an orifice quite at the posterior extremity of

the body. There is a sac, the bursa copulatrix or copulatory pouch, which

is prolonged in a tubular manner, to open externally on the eighth ventral

plate: a tube, the seminal duct, connects the bursa with the oviduct, and

on this tube there may be a dilatation—the spermatheca. Besides these

structures two sets of accessory glands open into the oviduct, an unpaired

gland, and a pair of glands. The development of these structures has been

described by Hatchett Jackson,[180] and exhibits some very interesting

features. The exact functions of the bursa copulatrix and of the other

structures are by no means clear. According to Riley,[181] the spermatheca

in _Pronuba_ contains some curious radiate bodies, and Godman and Salvin

describe something of the same sort as existing in butterflies. Several

variations in the details of the structure of these remarkably complex

passages have been described, and the various ducts are sometimes rendered

more complex by diverticula attached to them. Some noteworthy diversities

in the main anatomical features exist. According to Cholodkovsky, there is

but one sexual aperture—the posterior one—in _Nematois metallicus_; while,

according to Brandt, the number of egg-tubes in a few cases exceeds the

normal—four—being in _Sesia scoliaeformis_ fourteen. In _Nematois

metallicus_ there is individual variation, the number of tubes varying from

twelve to twenty.

The EGG has been more extensively studied in Lepidoptera than in any other

Order of Insects. It displays great variety: we meet with elongate forms

(Fig. 164) and flat forms like buttons, while in _Limacodes_ (Fig. 83, Vol.

V.) the egg is a {322}transparent scale of somewhat inconstant outline.

Some are coloured and mottled somewhat after the fashion of birds'-eggs;

this is the case with some eggs of Lasiocampidae and Liparidae; in some the

sculpture of the egg-shell is of the most elaborate character (Figs. 77,

78, Vol. V.). The egg-shell or chorion is, according to Korschelt[182] and

others, a cuticular product of the epithelium of the egg-chambers of the

ovaries. The number of eggs deposited by an individual differs greatly in

different species, and has been ascertained to be variable within certain

limits in the same species. Speyer thought about 250 to be the average

number of eggs deposited by an individual. The number in the case of

_Aporia crataegi_ is believed to be from 60 to 100, and in some _Hepialus_

to be several thousands. The mode of deposition also differs greatly; where

the eggs are very numerous they seem to be discharged almost at random in

suitable spots; but moths such as _Clisiocampa neustria_ fasten their eggs

round the stems of the food-plant in a very perfect and artistic manner.

Butterflies seem as a rule to prefer to oviposit by placing an egg here and

there rather than risk many in one situation; but to this there are many

conspicuous exceptions especially in the cases where the larvae live

gregariously, as in the Vanessae. Some moths cover the eggs with fur from

their own body, which, in the case of certain of the Eggers

(Lasiocampidae), seems to have a special supply for the purpose. The period

that intervenes between deposition and hatching of the eggs varies from a

few days to many months. There seems to be, as a rule, comparatively little

power of extending the period of latency beyond a single season; though

certain facts have been recorded that would lead us to believe that in

Australia eggs may last over the proper time during a drought, and be

hatched as soon as rain falls.

[Illustration: Fig. 164—Egg of Orange-tip butterfly, _Euchloe cardamines_,

magnified. _a_, The egg of natural size on a stalk.]

LARVA.—The young condition or larva of the Lepidopterous Insect is commonly

called a caterpillar. It is a somewhat worm-like creature—in old English

it was sometimes called {323}palmer-worm—and is composed of a head and

thirteen divisions or segments of the body; the first three of the latter

are called thoracic, the other ten, abdominal segments; in most

caterpillars the terminal two or three abdominal segments are more or less

run together, and the ninth may be very small, so that the true number is

indistinct. The first three segments bear each, on either side, a short

limb, ending in a curved spine; the next two (or three or more) segments

are destitute of legs, but on some of the following divisions another kind

of leg of a more fleshy character appears, while the body is terminated by

a pair of these thick legs of somewhat different form. The front legs are

usually called the true legs, the others prolegs, but this latter

designation is a most unfortunate one, the term "pro" being in entomology

used to signify anterior; it is therefore better to call the three anterior

pairs thoracic legs, and the others abdominal feet, distinguishing the hind

pair of these latter as claspers. There is, too, an unfortunate discrepancy

amongst entomologists in their manner of counting the body-segments, some

count the head as the first segment, while others apply this term to the

first thoracic segment. The latter is the more correct course, for, as the

head is not a single segment it should not be called such in a terminology

that affects to be morphologically exact, not simply descriptive. The

thoracic legs are transversely jointed (Fig. 165, B), but this is not the

case with the abdominal feet, which are usually armed beneath with a

circle, or with rows, of little hooks. The thoracic legs are, independent

of their form, of a different nature from the abdominal, for these latter

disappear subsequently, while the former give rise to the legs of the

imago. The number of thoracic legs is always six, except in a few cases

where there are none at all; the abdominal feet are much more variable, and

exhibit so many distinctions that we cannot here attempt to deal with them.

M. Goossens has given a concise and interesting account of this

subject,[183] and Speyer[184] a summary of the variety in number and

position.

The anatomy of the larva is simple in comparison with that of the perfect

Insect; its main features will be appreciated from Fig. 165, from which it

will be seen that the stomach is enormous, and the silk-vessels are also

very extensive.

{324}[Illustration: Fig. 165.—A, Section of male caterpillar of _Anosia

plexippus_—muscular and tracheal systems and fat-body not shown: I, pro-,

II, meso-, III, meta-thorax; 1-10, abdominal segments; _b_,

supra-oesophageal ganglion; _c_, rectum; _d.v_, dorsal vessel; _g^3-g^9_,

ganglia of ventral chain; _h_, head; _i_, intestine; _m.v_, Malpighian

tube; _n.c_, nerve-cord of ventral chain; _oe_, oesophagus; _s_, spinneret;

_s.o.g_, infra-oesophageal ganglion; _st_, stomach; _s.v_, silk-vessel;

_t_, testis. B, One of the jointed prothoracic legs. C, An abdominal foot

with its hooks. (After Scudder and Burgess, magnification about 2/1.)]

There are three sets of glands opening by canals on the head, viz. the

salivary glands proper, which open into the cavity of the mouth, one close

to the base of each mandible; the silk-glands, which terminate by a common

canal, continued externally as the spinneret; and the glands of Filippi

situate in the head itself, and opening into the ducts of the silk-glands,

near their union into a common duct. It should be recollected that Fig. 165

does not indicate all the details of the anatomy; the muscular system, for

instance, being entirely omitted, though there are an enormous number of

muscles; these however are not very complex, they being mostly repetitions

in the successive segments.[185] The mouth-parts are very different from

those of the perfect Insect, inasmuch as the maxillae and labial palpi,

which are the most remarkable structures of the imago, are small, and are

differently constructed in the caterpillar, while the mandibles, which are

the largest organs of the caterpillar, disappear in the adult. The little

organ by which the caterpillar exudes its silk is called a spinneret;

according to Packard it is a "homologue of the hypopharynx." It is a more

or less prominent point on the middle of the labium (Fig. 166, _g_) and

sometimes forms a conspicuous spine projecting downwards. The eyes are

extremely imperfect organs, consisting merely of six, in some cases

{325}fewer, transparent, somewhat prominent, little spaces placed on each

side of the lower part of the head; they are called "ocelli," by Landois

"ocelli compositi." Under each of these external facets there are placed

percipient structures, apparently very imperfect functionally, the

caterpillar's sight being of the poorest character.[186] The spiracles of

the caterpillar are nine on each side, placed one on the first thoracic

segment and one on each of the first eight abdominal segments; there are no

true stigmata on the second and third thoracic segments, though traces of

their rudiments or vestiges are sometimes visible.

[Illustration: Fig. 166—Front view of head of a caterpillar, with the jaws

partially opened, _a_, Labrum; _b_, mandible; _c_, antenna; _d_, ocelli;

_e_, maxilla; _f_, lingua; _g_, spinneret; _h_, labial palp.]

In the caterpillar there are no traces of the external sexual organs, so

that the two sexes cannot be distinguished on superficial inspection; it

was however long ago demonstrated by Herold[187] that the ovaries and

testes exist in the youngest caterpillars, and undergo a certain amount of

growth and development in the larval instars; the most important feature of

which is that the testes are originally separate but subsequently coalesce

in the middle line of the body, and become enclosed in a common capsule. In

a few forms—especially of Liparidae—(Lymantriidae of modern authors)—the

caterpillars are said to be of different colours in the two sexes. Most of

what is known on this point has been referred to by Hatchett Jackson.[188]

The Silk-glands of Lepidoptera are of great interest from the physiological

point of view, as well as from the fact that they have furnished for many

ages one of the most beautiful of the adornments made use of by our own

species. The sericteria, or vessels that secrete silk, are of simple

structure, and differ greatly in their size in the various forms of the

Order; they sometimes become of great length; in the Silk-worm each of the

two vessels is nearly five times as long as the body, while in _Bombyx

yamamai_ and others, even this is exceeded. They {326}grow with remarkable

rapidity, being in the young silk-worm only 3 mm. long, in the adult 22 mm.

The increase in weight is still more remarkable; when the silk-worm is

thirty-one days old, the sericteria weigh only 3 mgr., but when the age is

fifty days their weight has increased to 541 mgr., being then ⅖ of the

whole weight of the body. In the pupa they undergo a gradual atrophy, and

in the moth they are, according to Helm, no longer to be found, though

earlier authors were of a contrary opinion.[189] According to Joseph,[190]

the silk-vessels begin to develop at an extremely early age of the embryo,

and are very different in their nature from the salivary glands, the former

being derivatives of the external integument (ectoderm), while the salivary

glands belong to the alimentary system. This view is to some extent

confirmed by the observations of Gilson as to the different manner in which

these two sets of glands discharge their functions.

The chief feature in the anatomy of the larva is the great size of the

stomach. There is a very short oesophagus and crop; the latter becomes

enlarged, spreading out so as to form the stomach, a great sac occupying

the larger part of the body-cavity (Fig. 165). On the hinder end of this

sac the Malpighian tubes open; they are similar in their disposition to

those of the imago; behind the stomach the canal expands into two

successive, short dilatations, the first called an intestine, the second a

rectum; they are connected by very short isthmuses. The dorsal vessel is a

simple, slender tube, extending from the eighth abdominal segment to the

head. The main nervous system consists of supra- and infra-oesophageal

ganglia, a small frontal ganglion, and a ventral chain of eleven ganglia,

three thoracic and eight abdominal, the last of these latter being double.

The sexual organs are quite rudimentary, and the passages connected with

them very incompletely developed.

PUPA.—The pupa, which is one of the most remarkable of the instars of an

Insect's life, attains its highest development in Lepidoptera. The

Lepidopterous pupa is frequently called a "chrysalis," a term originally

applied to certain metallic butterfly pupae. The Lepidopterous pupa differs

from that of other Insects in the fact that its outer skin forms a hard

shell, all the appendages of {327}the body being glued together by an

exudation so as to form a single continuous outer skin. This form of

perfect pupa is called "pupa obtecta." The obtected pupa is exhibited in

various stages of perfection in the Lepidoptera; the maximum of perfection

is attained by the pupae of such butterflies as are exposed without

protection or concealment; on the other hand, we find in various small

moths conditions of the pupa that do not differ in any marked manner from

the pupae of Insects of other Orders. Moreover, certain Coleoptera and

Diptera exhibit obtected pupae of a more or less perfect kind. Hence the

pupa obtecta is to be considered as a perfected condition that exists more

frequently in the Lepidoptera than in other Orders.

[Illustration: Fig. 167.—Section of female pupa of _Anosia plexippus_, 3-4

days old. I, pro-, II, meso-, III, meta-thorax; 1-9, abdominal segments;

_a_, antenna(?); _ac_, aortal chamber; _ag^1-ag^5_, abdominal ganglia;

_agl_, accessory glands; _ao_, aorta; _br_, brain; _c_, colon; _cp_, bursa

copulatrix; _cr_, cremaster; _f^1_, first femur; _fr_, food-reservoir; _h_,

dorsal vessel; _i_, part of intestine; _mv_, Malpighian tube; _mx_, base of

maxilla; _oe_, oesophagus; _ov_, ovary; _ph_, pharynx; _sd_, salivary duct;

_sgl_, salivary gland; _st_, stomach; _t^1_ first tarsus; _tg_, compound

thoracic ganglion; _ts^2_, _ts^3_, second and third tarsus. (After

Scudder.)]

The pupa has no orifices to the alimentary canal or sexual organs, but the

respiratory openings are pervious. It has no means of locomotion, but it

can move a certain number of the posterior segments (the number variable

according to kind). In some cases it is provided with spines, "adminicula,"

by means of which, aided by the wriggling movements of the abdominal

segments, considerable changes of position can be effected. The pupae of

the genus _Micropteryx_ apparently use the legs for locomotion, as do the

pupae of Trichoptera.

The study of the pupa of Lepidoptera is less advanced than that of the

imago and larva, between which it is, in many points of structure,

intermediate.[191] The interior of the pupa contains a {328}quantity of

cream-like matter, including the results of histolysis—but this, as well as

the condition of the internal organs, differs much according to whether the

change from the caterpillar to the moth is much or little advanced.

Many pupae are protected by cocoons. These are masses of silk—very various

in form—disposed by the caterpillar around itself during the last stage of

its existence. Some of these cocoons are so perfect that the moth has

considerable difficulty in escaping when the metamorphosis is complete.

Various devices are used for the purpose of emergence; the Puss-moth

excretes a corrosive fluid, containing potassium hydroxide, and then

protects itself from this by retaining on the head while passing through it

a shield formed of a portion of the pupa-skin.[192] Lepidopterous pupae

usually have the body terminated by a projection of very various and

peculiar form called "cremaster." In certain cases these projections are

used for the suspension of the pupa, and are then frequently provided with

hooks (Fig. 177, C, D). In other cases the cremaster is frequently called

the anal armature (Fig. 205, B).

[Illustration: Fig. 168—Wing-rudiments of _Pieris brassicae_. A, Rudiments

of a wing before the first moult of the caterpillar: _ce_, embryonic cells;

_ch_, external cuticle; _h_, hypodermis; _o_, opening of the invagination;

_tr_, trachea. B, posterior wing-rudiment of full-grown caterpillar; _b_,

semicircular pad; _c_, a bundle of the rolled tracheae; _e_, envelope; _i_,

pedicel; _tr_, trachea. (After Gonin.)]

The DEVELOPMENT of the WINGS of Lepidoptera has recently been much studied.

It has been known since the time of Lyonnet, that the rudiments of the

wings exist inside the body of the caterpillar when it is nearly adult.

Verson considers that he has detected the rudiments in the silk-worm larva

even before hatching, and he attributes their origin to a modification of

form of those hypodermal cells that occupy the spots where the spiracles of

the second and third thoracic segments might be looked for. (It will be

recollected that there are no spiracles on these two thoracic segments in

Lepidopterous larvae). Gonin has examined the wing-rudiments in the

caterpillar, a few days old, of {329}_Pieris brassicae_,[193] and finds

that the future wing is then indicated by a thickening and bagging inwards

of the hypodermis, and by some embryonic cells and a trachea in close

relation with this mass (Fig. 168, A). The structure grows so as to form a

sac projecting to the interior of the body, connected with the body-wall by

a pedicel, and penetrated by a trachea forming branches consisting of

rolled and contorted small tracheae (Fig. 168, B). If the body-wall be

dissected off the caterpillar immediately before pupation the wings appear

in crumpled form, as shown in Fig. 169. This fact was known to the older

entomologists, and gave rise to the idea that the butterfly could be

detected in a caterpillar by merely stripping off the integument.

The exact mode by which the wings become external at the time of appearance

of the chrysalis is not ascertained; but it would appear from Gonin's

observations that it is not by a process of evagination, but by destruction

of the hypodermis lying outside the wing. However this may be, it is well

known that, when the caterpillar's skin is finally shed and the chrysalis

appears, the wings are free, external appendages, and soon become fastened

down to the body by an exudation that hardens so as to form the shell of

the chrysalis.

[Illustration: Fig. 169—Anterior parts of a caterpillar of _P. brassicae_,

the body-wall having been dissected off, immediately before pupation. _a_,

_a′_, Anterior and posterior wings; _st I_, first spiracle; _p_, _p′_,

second and third legs. (After Gonin.)]

SCALES AND NERVURES.—Before tracing the further development it will be well

to discuss the structure of the scales and nervures that form such

important features in the Lepidopterous wing.

If a section be made of the perfect wing of a Lepidopteron, it is found

that the two layers or walls of the wing are firmly held together by

material irregularly arranged, in a somewhat columnar manner. The thickness

of the wing is much greater where the section cuts through a nervure (Fig.

170, A). The nervures apparently differ as to the structures found in them.

Spuler observed in a nervure of _Triphaena pronuba_, a body having in

section a considerable diameter, that he considered to be a {330}trachea,

and also a "wing-rib" and blood-cells. He remarks that even in nervures,

perfectly formed as to their chitinous parts, either wing-rib or trachea or

both may be absent.[194] Schäffer[195] was unable to find any tracheae in

the completed wings he examined, and he states that the matrix of the

tracheae and even their inner linings disappear. The wing-ribs were,

however, found by him to be present (Fig. 170, A and B).

[Illustration: Fig. 170.—Structure of wing of imago. A, Transverse section

of basal portion of wing [of _Vanessa_?] containing a nervure; _c_,

cuticle; _fr_, wing-rib; _g_, wall of nervure ("Grundmembran"); _h_,

hypodermis; _p_, connecting columns: _r_, lumen of nervure; B, section of a

rib; _b_, one of the chitinous projections; _str_, central rod. (After

Schäffer.)]

[Illustration: Fig. 171—Scales of male _Lepidoptera_. A, Scale from upper

surface of _Everes comyntas_; B, from upper surface of _Pieris rapae_; C,

from inner side of fold of inner margin of hind wing of _Laertias

philenor_; D, one of the cover-scales from the costal androconium of

_Eudamus proteus_; E, F, G, scales from androconium of _Thorybes pylades_.

(After Scudder).]

The scales that form so conspicuous a feature in Lepidoptera exist in

surprising profusion, and are of the most varied forms. They may be briefly

described as delicate, chitinous bags; in the completed state these bags

are flattened, so as to bring the sides quite, or very nearly, together.

Their colour is due to contained pigments, or to striation of the exposed

surface of the scale; the latter condition {331}giving rise to metallic

"interference-colours." The walls of the scales are themselves, in some

cases, tinted with pigment. It is said that some of the scales contain

air, and that the glistening whiteness of certain scales is due to this.

The exposed surface of the scale usually differs from the surface that is

pressed down on the wing in being delicately and regularly striated; the

colours of the upper and under surfaces of a scale may also be quite

different. Scales are essentially of the nature of hairs, and all the

transitions between hairs and true scales may be found on the wings of

certain Lepidoptera that bear both hairs and scales, e.g. _Ithomia_. It has

been calculated that there are a million and a half of scales on the wings

of an individual of the genus _Morpho_. The scales are arranged on the wing

in an overlapping manner, somewhat like slates on the roof of a house.

Each scale has a short stalk, and is maintained in position by the stalk

fitting into a cavity in a projection of the wing-membrane (Fig. 172).

[Illustration: Fig. 172—Insertion of scales. A, Socket holding the stalk in

_Galleria mellonella_; B, insertion of the scale of _Polyommatus phloeas_.

_b_, Base of scale; _r_, holding-ring; _w_, surface of wing. (After

Spuler.)]

ANDROCONIA.—The males of numerous butterflies possess scales peculiar in

kind and various in arrangement. They may be either irregularly scattered

over the wing, or they may form very complex definite structures (Fig.

173). They were formerly called "plumules," but Scudder has replaced this

name by the better one, "androconia." The function of the androconia is

still obscure. An odour is believed to be connected with them. Thomas

supposes[196] that these scales are hollow tubes in connection with glands

at their bases, and that matter secreted by the glands passes through the

scales and becomes diffused. In nearly all Lepidoptera it is the male that

seeks the female; if therefore odorous scales were present in one sex only

we should have supposed that this would have been the female rather than

the male. As, however, the reverse is the case, the function of the

androconia is supposed to be that of charming the female. Scudder considers

that the covering part of the androconial {332}structures is sometimes

ornamental. As a rule, however, the "brands" of male Lepidoptera detract

from their beauty to our eyes.

[Illustration: Fig. 173—A, section of part of wing showing the complex

androconia of _Thanaos tages_, a Skipper butterfly. The turning over of the

costal margin of the wing is in this case part of the arrangement. _a_,

Upper covering-scales attached to the costal portion of the under surface

of the wing; _b_, edge of costal margin of the wing; _c_, costal nervure

with its scales; _d_, field of the wing next the costal nervure, bearing

stunted scales; _e_, the androconia proper, or male scales; _f_, posterior

covering scales; _g_, lumen of the costal nervure: B, a portion of the

costal area flattened out and seen from above; lettering as before: C,

section of androconium on the second nervure of _Argynnis paphia_. (After

Aurivillius.)]

Resuming our consideration of the DEVELOPMENT of the WINGS, we may remark

that the history of the changes during the pupal state is still imperfect.

By the changes of relative size of the thoracic segments the hind wing is

brought to lie under the anterior one (_i.e._ between it and the body), so

that in the newly formed pupa the arrangement is that shown in Fig. 174.

The wings are two sacs filled with material surrounding peritracheal spaces

in which run tracheae. The subsequent history of the tracheae is very

obscure, and contrary opinions have been expressed as to their growth and

disappearance. We have alluded to the fact that in some nervures tracheae

are present, while in others they are absent; so that it is quite possible

that {333}the histories of the formation of the nervures and of their

relation to tracheae are different in various Lepidoptera. This conclusion

is rendered more probable by the statement of Comstock and Needham,[197]

that in some Insects the "peritracheal spaces" that mark out the position

of the future nervures are destitute of tracheae. Gonin thinks the nervures

are derived from the sheaths of the peritracheal spaces, and a review of

all the facts suggests that the tracheae have only a secondary relation to

the nervures, and that the view that a study of the pupal tracheae may be

looked on as a study of the preliminary state of the nervures is not

sufficiently exact. It is, however, probable that in Lepidoptera the pupal

tracheae play an important though not a primary part in the formation of

the nervures; possibly this may be by setting up changes in the cells near

them by means of the air they supply. Semper long ago discovered hypodermal

cylinders traversed by a string (Fig. 170, B), placed near the tracheae in

the pupa.[198] It appears probable that the "wing-ribs" found in the

nervures (Fig. 170, A _fr_ and B) are the final state of these cylinders,

but the origin and import of the cylinders are still unknown.

[Illustration: Fig. 174—Transverse section of part of the newly disclosed

chrysalis of _Pieris brassicae_, showing the position and structure of the

wings, hanging from one side of the body. _aa_, Anterior wing; _ap_,

posterior wing; _e_, _e_, peritracheal spaces; _t_, _t_, tracheae. (After

Gonin.)]

The formation of the scales of the wing commences very early—apparently

soon after the casting of the larval skin—though the completion of the

scales and their pigmentation is delayed to a late period of the pupal

life. The scales are formed by special cells of the hypodermis that are

placed deeper in the interior of the wing than the other hypodermal cells.

Each scale is formed by one cell, and protrudes through the overlying

hypodermis; the membrane into which the scales are inserted is a

subsequently developed structure, and the beautiful {334}articulation of

the scale with the wing takes place by a division of the stalk of the scale

where it is encompassed by the membrane. Semper was not able to show that

the scale-forming cells are certainly hypodermal cells, but this has since

been demonstrated by Schäffer, who also shows that each of the cells

contains an excretory vesicle.

[Illustration: Fig. 175.—Early condition of scales and nervures. (After

Semper.) A, Section of portion of wing of pupa of _Sphinx pinastri_; _a_,

basal membrane with trachea beneath it; _c_, scale-forming cell; _d_, early

state of a scale; _e_, _e_, more advanced stages; _f_, hypodermal cells. B,

part of a cellular cylinder that excretes the nervure [or more probably the

rib or "Rippe" of Schäffer; cf. Fig. 170, B]; _b_, epithelial [hypodermal]

cells; _a_, central string [supposed by Semper to be a nerve].]

Very little is positively known as to the development of the colour in the

wing-scales. It has been pointed out by Hopkins[199] that in some cases the

colours are of the nature of urates; that is, of excretory matter of the

kind that usually passes from the body by direct channels, and in the case

of Lepidoptera, by the Malpighian tubes. Miss Newbigin suggests that the

organic pigments used in scale-coloration will be found to be of two kinds,

urates and melanins, the urates being derivatives from nitrogenous, the

melanins from carbonaceous, matters.[200] Marchal, who has devoted a great

deal of attention to the study of the Malpighian tubes, informs us that the

subdermal pigments of caterpillars are frequently in large part deposits of

urates, and he is of opinion that, the function of the Malpighian tubes

being arrested at certain periods of the metamorphosis, elimination of the

matter they separate when functionally active then takes place in a variety

of other ways.[201] A similar condition as to the melanin-pigments and the

respiratory functions appears also {335}probable. The scales when first

formed are pallid, and the physiology of their pigmentation is not fully

ascertained; it is, however, known that when the scales are pallid the

hypodermis is either pigmented or in close contact with pigmentary matter,

and that as the scales become coloured this pigmentation of the hypodermis

diminishes; so that it is clear that the colour of the scales is obtained

from matter in the interior of the developing wing, and probably by the

agency of the hypodermis.