_Nervous System_. A small bilobed brain crowning a double, k_An Introduction to Entomology: Vol. 3 or Elements of the Natural History of the Insects

medullary chord; nerves proceeding from the brain and other

ganglions to all parts of the body.

CIRCULATION.

_Heart_ unilocular, inaurite, with a system of circulation by

arteries and veins; blood a cold white sanies.

RESPIRATION.

_Lungs_ replaced by internal gills receiving the air by spiracles.

DIGESTION.

_Liver_, consisting of conglomerate glands, and enveloping the

intestines[49]; hepatic ducts.

GENERATION.

_Genital organs_ double, ventral; more than one sexual union in the

course of life.

The external characters in this class are the same almost in

every respect as those which distinguish the _Phalangidæ_, the

whole difference consisting almost in the systems of circulation,

respiration, and digestion. Perhaps some future anatomist may

discover in the tribe just mentioned, that there is a nearer

agreement between them and the _Arachnida_ in these systems than is

at present suspected, which would prove them true _Arachnida_. I am

inclined to think that _Phrynus_ and _Gonyleptes_, &c. breathe by

branchial spiracles; but having no opportunity of examining living

specimens, I dare not speak with any confidence on the subject.

* * * * *

Having thus given you a view of the most important diagnostics by

which what we have all along called _Insects_ may scientifically be

distinguished from other invertebrate animals, it may not be without

use, if, under this head, I take a more _popular_ and familiar view

of the subject, and say something upon those distinctions which may

attract the attention of the more common observer.

The notion of diminutive size, particularly as compared with

vertebrate animals, seems more frequently attached to the idea of

an insect than any other; and this notion is generally correct,

for one insect that is bigger than the least of the above animals,

thousands and thousands are vastly smaller: but there exist some

that are considerably larger, whether we take length or bulk into

consideration, and this in almost every order. To prove this

most effectually, and that you may have a synoptical view of the

comparative size of the larger insects of the different orders and

tribes, I now lay before you a table of the dimensions of such of

the largest as I have had an opportunity of measuring, including

particularly those giants that are natives of the British isles.

Explanation of Table:

Column A - Length Inches

B - Breadth Inches

C - Expansion of Wings Longitudinal Inches} See note in table

D - Expansion of Wings Transverse Inches }

_Order and | _Species._ | A | B | C | D |

| | | | | |

| | | | | |

CICINDELIDÆ |_Manticora grandis_ |1-5/8 | 7/10| | |

| | | | | |

ANTHIADÆ |_Anthia sexguttata_ |1-7/8 | 7/10| | |

| | | | | |

CARABIDÆ |_Carabus scabrosus_ |1-3/4 | 8/10| | |

| | | | | |

DYTISCIDÆ |_Dytiscus latissimus_|1-1/2 |1 | | |

| | | | | |

STAPHYLINIDÆ |_Staphylinus olens_ |1-1/2 | 5/10| | |

| Br. | | | | |

| | | | | |

HYDROPHILIDÆ |_Hydrophilus piceus_ |1-3/4 | 7/8 | | |

| Br. | | | | |

| | | | | |

BUPRESTIDÆ |_Buprestis grandis_ |2-1/2 |1 | | |

| | | | | |

|--------- _bicolor_ |2-5/12| 3/4 | | |

| | | | | |

DYNASTIDÆ |_Dynastes Hercules_ |4-1/2 |2-1/2 | | |

| | | | | |

|_Megasoma Actæon_ K. |4-1/4 |2-1/4 | | |

| | | | | |

CETONIADÆ |_Goliathus giganteus_|3-7/10|1-9/10| | |

| | | | | |

LUCANIDÆ |_Lucanus Cervus_ Br. |2 | 7/10| | |

| | | | | |

TENEBRIONIDÆ |_Tenebrio grandis_? |1-7/10| 7/10| | |

| | | | | |

BRENTIDÆ |_Brentus_ N. S. Mus. |2-1/10| 2/12| | |

| | | | | |

CALANDRIDÆ |_Calandra_ N. S. Mus.|3-5/8 |1 | | |

| | | | | |

BRACHYCERIDÆ |_Brachycerus apterus_|1-5/8 | 7/8 | | |

| | | | | |

|_Brachycerus_ |2 | 9/10| | |

| | | | | |

PRIONIDÆ |_Prionus grandis_ |6-1/2 |2-3/8 | | |

| | | | | |

|---- _cervicornis_ |5-1/2 |1-5/8 | | |

| | | | | |

|Do. |4-1/4 | | | |

| | | | | |

|---- _coriarius_ Br. |1-6/10| 7/10| | |

| | | | | |

LAMIADÆ |_Lamia grandis_ |2-3/4 |1 | | |

| | | | | |

CHRYSOMELIDÆ |_Chrysomela_ N. S. |1-1/4 | 3/4 | | |

| | | | | |

HISPIDÆ |_Alurnus grossus_ |1-3/10| 6/10| | |

| | | | | |

EROTYLIDÆ |_Erotylus grandis_ |1-6/10| 6/10| | |

| | | | | |

| | | | | |

|_Labidura gigantea_ |1-1/4 | | | |

| Br.? |nearly| | | |

| | | | | |

|_Forficula_ N. S. N. |1-4/5 | 2/5 | | |

| Holl. | | Do. | | |

| | | | | |

| | | | | |

BLATTIDÆ |_Blatta gigantea_ |2-5/8 |1-1/2 | | |

| | | | | |

|---- N. S. MacLeay |3-3/10|1-1/2 | | |

| | | | | |

PHASMIDÆ |_Phasma grandis_ |7 | 7/8 | | |

| | | | | |

|---- _australensis_ |8-1/2 | 3/4 |7-1/2 |2-3/4 |

| K. | | | | |

| | | | | |

| | | | | |

LOCUSTIDÆ |_Locusta Dux_ |4-3/8 | |8-1/4 |2 |

| | | | | |

| Br. | | | | |

| | | | | |

* | | | | | |

| | | | | |

FULGORIDÆ |_Fulgora laternaria_ |3 | |5-6/10|2 |

| | | | | |

CICADIADÆ |_Cicada_ N. S. N. |2-1/10| |5-1/2 | |

| | | | | |

** |Do. |2-8/10| | | |

| | | | | |

NEPIDÆ |_Belostoma grandis_ |3 | |5-6/10|1-3/10|

| | | | | |

LYGEIDÆ |_Lygæus Pharaonis_ |2 |1 | | |

| | | | | |

* | | | | | |

| | | | | |

PAPILIONIDÆ |_Papilio Remus_ | | |8-3/4 |3-5/8 |

| | | | | |

|---- _Priamus_ |2-1/2 | |7-6/10|3 |

| | | | | |

|---- _Machaon_ Br. |1 | |3-1/2 |1-1/2 |

| | | | | |

NYMPHALIDÆ |_Morpho Teucer_ |1-7/10| |7-1/2 |4-1/2 |

| | | | | |

SPHINGIDÆ |_Sphinx_ N. S. Brazil|2-1/2 | 7/10|6-1/2 | |

** | | | | | |

| | | | | |

SPHINGIDÆ |_Sphinx Atropos_ Br. |2 | 5/8 |4-3/4 |1-1/2 |

*** | | | | | |

| | | | | |

BOMBYCIDÆ |_Attacus Atlas_ |1-3/4 | |8-3/4 |5-1/2 |

| | | | | |

|_Gastropacha |1-1/4 | |3-1/2 |1-1/4 |

| | | | | |

NOCTUIDÆ |_Erebus Strix_ |2 1/4 | |10-3/4|3-1/4 |

| | | | | |

| | | | | |

AGRIONIDÆ |_Agrion lineare_ |5-1/2 | |5 | |

| | | | | |

| | | | | |

MYRMELEONIDÆ |_Myrmeleon |2 | |5 | |

| | | | | |

SEMBLIDÆ |_Corydalis cornuta_ |2-3/4 | |5-1/4 | |

| | | | | |

|Do. |2 | | | |

| | | | | |

| | | | | |

| | | | | |

POMPILIDÆ |_Pompilus ocellatus_ |2-1/8 | |3-1/2 | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

TIPULIDÆ |_Tipula sinuata_ Br. |1-3/8 | |2-1/2 | |

| | | | | |

| | | | | |

| Br. | | | | |

| | | | | |

| | | | | |

|---- _bovinus_ Br. |1 | | | |

| | | | | |

* | | | | Legs_ |

| | | | |

SCOLOPENDRIDÆ|_Scolopendra_ N. S. |13 |7/8 | |

** | | | | |

| | | | |

IULIDÆ |_Iulus_ N. S. Do. |5-1/2 |8/10 | |

| | | | |

PHALANGIDÆ |_Gonyleptes_ N. S. | 3/8 | | 6 |

| | | | |

| | | | |

| | | | |

| | | | |

ARANEIDÆ |_Mygale_ N. S. Do. |3 |1-1/2 | 11 |

From this table you see that several insects included in it exceed

some of the smallest _Vertebrata_ in bulk. In the _Mammalia_, the

_Sorex Araneus_, called by the common people here the Ranny, is

not more than two inches long excluding the tail; and the _Mus

messorius_, or harvest-mouse, peculiar to the southern counties of

England, is still more diminutive: so that to these little animals,

the larger _Dynastidæ_, _Goliathi_, and _Prioni_, &c., appear giants,

and may compete with the mole in size. Even some of the beetles

of our own country, as the great _Hydrophilus_, the stag-beetle,

&c., are more bulky than the two first-named quadrupeds. Amongst

the birds, many _Picæ_, _Passeres_, &c., yield to several insects

in dimensions, and their wings when expanded do not extend so far

as those of not a few _Lepidoptera_. The great owl-moth of Brazil

(_Erebus Strix_) in this respect is a larger fowl than the quail.

Those beautiful little creatures, the humming-birds (_Trochilus_ L.),

the peculiar ornament and life of tropical gardens, which emulate the

most splendid butterflies in the brilliancy of their plumage, are

smaller than a considerable number of insects in almost every order,

and even than some of those that are natives of Britain. Various

reptiles also are much inferior in size to many of the insects of the

above table. The smallest lizard of this country would be outweighed

by the great British beetles lately mentioned, and the mole-cricket

(_Gryllotalpa vulgaris_); and some of the serpent tribe are smaller

than the larger _Scolopendræ_ and _Iuli_. Amongst the _fishes_ also,

though some are so enormous in bulk, others in this respect yield

the palm to several insects. The _minnow_ and the _stickleback_ that

frequent our own pools and streams are considerably inferior in size

to some of our water beetles.

In looking over the table, and comparing the different species that

compose it with each other, you will perceive that the largest

insects of the two sections of _Hemiptera_, of the _Lepidoptera_

as to their _body_ merely, of the _Hymenoptera_ and _Diptera_, in

general size fall considerably short of those of the other orders;

and that certain individuals of the _Orthoptera_ and _Aptera_ bear

away the palm in this respect from all the rest. In the _Coleoptera_

the giants, with the exception of the _Goliathi_, are chiefly to

be found amongst the timber devourers in the _Lamellicorn_ and

_Capricorn_ tribes. Of orthopterous insects the _Phasmidæ_ present

the most striking examples of _magnitude_; and in the _Neuroptera_,

the _Agrionidæ_ of great _length_.

It is worthy of remark here, that although the tropical species

of a genus usually exceed those of colder climates in size, the

_Gryllotalpa_ of Brazil is very considerably smaller than that of

Europe: whether this is the case with the rest of the cricket tribe I

have not had an opportunity of ascertaining. The _Lepidoptera_, though

often remarkable for the vast expansion of their "sail-broad vans," if

you consider only their bodies, never attain to gigantic bulk. Even

the hawk-moths (_Sphinx_ L.), though usually very robust, make no

approach to the size of the great beetles, or the length of some of

the spectres (_Phasma_) and dragon-flies (_Agrionidæ_). With regard

to the superficial contents of their wings, a considerable difference

obtains in different species where they expand to the same length--for

the _secondary_ wings are sometimes smaller than the _primary_, and

sometimes they equal them in size. In some instances, also, the latter

although long are narrow, and in others they are nearly as wide as

long: regard, therefore, should be had to their expansion both ways.

In the _Hymenoptera_ and _Diptera_, the principal giants are to be

found in the predaceous or blood-sucking tribes, as _Scolia_, the

_Sphecidæ_, _Pompilidæ_, _Vespidæ_, &c., belonging to the former order;

and the _Asilidæ_ and _Tabanidæ_ to the latter. The true and false

humble bees (_Bombus_ and _Xylocopa_) and the fly tribe (_Muscidæ_),

though they sometimes attain to considerable size, scarcely afford

an exception to this observation. Amongst the _Aptera_ none of the

_Hexapods_ strike us by their magnitude, and few of the _Octopods_,

though the legs of some of the _Phalangidæ_ inclose a vast area. That

in the table would with them describe a circle of six inches diameter,

though its body is little more than a quarter of an inch in length.

The _Myriapods_ exceed most insects in the vast elongation of their

body, which with their motion gives them no slight resemblance to the

serpents. In the class _Arachnida_, the bird-spiders (_Mygale_) are

amongst the principal giants, nor do the _Scorpions_ fall far short of

them--both of them when alive often alarming the beholder as much by

their size as by their aspect.

But as I have before observed, generally speaking, one of the most

remarkable characters of the insect world, is the little space

they occupy; for though they touch the vertebrate animals and even

quadrupeds by their giants, yet more commonly in this feature they go

the contrary way, and by their smallest species reach the confines

of those microscopic tribes that are at the bottom of the scale of

animal life. I possess an undescribed beetle, allied to _Silpha

minutissima_ E. B.[50], which, though furnished with elytra, wings,

antennæ, legs, and every other organ usually found in the order it

belongs to, is absolutely not bigger than the full stop that closes

this period. In several other coleopterous genera there are also very

minute species, as in _Cryptophagus_, _Anisotoma_, _Agathidium_,

&c. I know no _orthopterous_ insect that can be called extremely

minute, except that remarkable one found on the Continent in the

nests of ants, the _Blatta Acervorum_ of Panzer[51], but now called,

I believe, _Myrmecophilus_: nor indeed any in the _Hemiptera_,

_Neuroptera_, and _Diptera_, that approach the extreme limits of

visibility: but in the _Lepidoptera_, the pygmy _Tinea occultella_

is almost invisible except in flight, being scarcely thicker than

a horse's hair, and proportionably short; indeed, many others of

those lovely Lilliputians, the subcutaneous _Tineæ_, decorated with

bands of gold and silver, and studded with gems and pearls, that in

larger species would dazzle the beholder's eye, are in size not much

more conspicuous. In the _Hymenoptera_ order, _Ichneumon Punctum_ of

Dr. Shaw, which forms so striking a contrast to his giant _Phasma

dilatatum_, being placed together in the same plate; and another

that I possess, under the trivial name of _Atomos_, would elude the

searching eye of the entomologist unless when moving upon glass.

Linné named the tribe of parasites to which these belong, _Minuti_,

on account of their generally diminutive size. But these little

minims, under the superintendence of Providence, are amongst the

greatest benefactors of the human race, since they keep within due

bounds the various destroyers of our produce.

The number of minute species of insects seems greatly to exceed

that of large ones, at least in Europe, of which it may be asserted

probably with truth, that two-thirds are under a quarter of an inch

in length, and one-third not exceeding much a duodecimal of it. It

might hold good perhaps in _Coleoptera_, _Hymenoptera_, _Diptera_,

and _Aptera_: but in _Orthoptera_, _Hemiptera_, _Neuroptera_, and

especially _Lepidoptera_, a large proportion would be found to exceed

three lines in length. Neither can it be affirmed of extra-European

species, of those at least preserved in cabinets, amongst which it

is rare to find an insect less than the fourth of an inch long.

This, however, must probably be attributed to the inattention of

collectors, who neglect the more minute species.

* * * * *

Though size forms a pretty accurate distinction between insects and

the great bulk of _vertebrate_ animals, it affords less assistance in

separating them from the _invertebrate_ classes, which are of every

size, from the monstrous bulk of some _Cephalopoda_ (cuttle-fish) and

_Mollusca_ (shell-fish, &c.) to the invisible infusory animalcule:

but external characters, abundantly sufficient for this purpose,

may be drawn from the general covering, substance, form, parts, and

organs of the body. As I shall enter into pretty full details upon

this subject when I come to treat of the external anatomy of insects,

I shall here, therefore, only give such a slight and general sketch

of the distinctions just mentioned, as will answer the end I have in

view. I must here repeat what I have before observed, and what it is

necessary that you should always bear in mind, namely, that at the

limits of classes and of every other natural group, the characters

begin to change, those peculiar to the one group beginning gradually

to disappear, and those of the other to show themselves; so that it

is impossible almost to draw up a set of characters so precise as

exactly in every respect to suit all the members of any natural group.

Whichever way we turn our eyes on the objects of creation,

above--below--athwart, _analogies_ meet us in every direction, and it

appears clear, that the Book of Nature is a Book of Symbols, in which

one thing represents another in endless alternation. And not only

does one animal, &c. symbolize another, but even between the parts

and organs of one set of animals there is often an _analogy_ as to

their _situation_ and _use_, when there is little or no _affinity_ as

to their _structure_--or again, the analogy is in their _situation_,

without affinity in either structure or use. Thus certain parts in

one tribe represent other certain parts of another tribe, though

as to their structure there is often a striking disagreement. This

is particularly observable between the vertebrate and invertebrate

animals. I shall therefore, in my remarks on the general and

particular structure of insects, contrast it in its most important

points with that of the first-mentioned tribe.

The first thing that strikes us when we look at an insect is its

outside _covering_, or the case that incloses its muscles and internal

organs. If we examine it attentively, we find that it is not like the

skin of quadrupeds and other _Vertebrata_, covering the whole external

surface of the body; but that in the large majority it consists of

several pieces or joints, in this respect resembling the skeleton

of the animals just named; and that even in those in which the body

appears to have no such segments, as in many of the Mites (_Acarus_

L.), they are to be found in the _limbs_. This last circumstance,

to have externally jointed legs, is the peculiar and most general

distinction by which the _Insecta_ of Linné, including the _Crustacea_,

may always be known from the other invertebrate animals[52].

If we proceed further to examine the _substance_ of this crust or

covering, though varying in hardness, we shall find it in most

cases, if we exclude from our consideration the shells of the

_Mollusca_, &c., better calculated to resist pressure than that of

the majority of animals that have no spine. In all the invertebrate

tribes, indeed, the muscles, there being no internal skeleton, are

attached to this skin or its processes, which of course is firmer

than the internal substance; but in insects it is very often rigid

and horny, and partially difficult to perforate, seldom exhibiting

that softness and flexibility which is found in the cuticle of birds

and most quadrupeds. From this conformation it has been sometimes

said, that insects carry their _bones_ on the _outside_ of their

body, or have an _external_ skeleton. This idea, though not correct

in all respects, is strictly so in this--that it affords a general

point of support to the muscles, and the whole structure is erected

upon it, or rather I should say within it. The difference here

between _Insects_ and the _Vertebrata_ seems very wide; but some of

the latter make an approach towards it. I allude to the Chelonian

Reptiles (_Testudo_ L.), in which the vertebral column becomes

external or merges in the upper shell. The _cyclostomous_ fishes also

are not very wide of insects as to their integument. But on this

subject I shall be more full hereafter.

The _forms_ of insects are so infinitely diversified that they almost

distance our powers of conception: in this respect they seem to

exceed the fishes and other inhabitants of the ocean, so that endless

diversity may be regarded as one of their distinctions. But on all

their variations of form the Creator has set his seal of symmetry; so

that, if we meet with an animal in the lower orders in which the parts

are not symmetrical, we may conclude in general that it is no insect.

But it is by their _parts_ and _organs_ that insects may be most

readily distinguished. In the _vertebrate_ animals, the body is

usually considered as divided into _head_, _trunk_, and _limbs_,

the _abdomen_ forming no part of the skeleton; but in the _insect_

tribes, besides the organs of sense and motion, the body consists of

_three_ principal parts--_Head_, _Trunk_, and _Abdomen_--the _first_,

as was before observed, bearing the principal organs of _sense_ and

_manducation_; the _second_ most commonly those of _motion_; and the

third those of _generation_--the organs of respiration being usually

common to both trunk and abdomen. These three primary parts,--though

in some insects the head is not separated from the trunk by any

suture, as for instance in the _Arachnida_; and in others, head,

trunk, and abdomen form only _one_ piece, as in some mites,--still

exist in all, and in the great majority they are separated by

incisures more or less deeply marked: this is particularly visible in

the _Hymenoptera_ and _Diptera_, which, in this respect, are formed

upon a common model; and in the rest, with the above exceptions, it

may be distinctly traced.

An Introduction to Entomology: Vol. 3 or Elements of the Natural History of the Insects · 第 2 / 53 段

_Nervous System_. A small bilobed brain crowning a double, knotty,