The tail of some species of the genusEphemerais furnished with three long, jointed, hairy bristles. We learn from Reaumur with respect to one, that though in the female these are all equal in length, yet in the male there is only a rudiment of the third. On the belly near the anus these males have four fleshy appendages, the posterior ones setaceous and long, and the anterior pair filiform and shorter. They are supposed to represent the anal forceps of other insects[888]. InEphemera vulgata, described by De Geer, both sexes have three bristles, but those of the male are the longest; and he describes the forceps as consisting of only a pair of jointed pieces, forming a bow not unlike the forceps of an earwig[889].
v. All the differences I have hitherto noticed between the sexes of insects occur in theirbodilystructure; but there are others of a somewhat higher description observable in theircharacter. You may smile at the idea of character in beings so minute; but if you recollect what I formerly related to you when treating upon the societies of insects, you will allow that something of this kind does take place amongst them. In general the males are more fitted for locomotion and more locomotive; and the females, on the contrary, are necessarily more stationary. And this for an obvious reason:—the law is, that the male shall seek the female, and therefore he is peculiarly gifted for this purpose, both in his organs of sensation and motion: while his partner in many cases has very simple antennæ, he has very complex ones; andwhile she has either no wings or only rudiments of them, he is amply provided with them. Again: amongst the insects that suck the blood of man or beast, such as the gnat (Culex) or horse-flies (Tabanidæ), it is the female alone that is bloodthirsty, the males contenting themselves with the nectar of flowers[890]. But the difference of character in the sexes is most conspicuous, at least it has been more noticed, in those that live in societies, and is quite the reverse of what takes place in the human species. While the females and workers (which are now generally considered as sterile females, in which the ovaries are not developed) are laborious and active, diligent and skilful, wise and prudent, courageous and warlike;—the males, on the contrary, take no part in promoting the common weal, except merely a sexual one. Though till a certain period they are supported at the expense of the community, they take no part in its labours, either in collecting and forming the public stores, or in feeding and attending the young. They are idle, cowardly, and inactive; have neither art nor skill of any kind, and are unprovided with the usual offensive weapons of their species. These observations in their full force apply particularly to the hive-bee, and partially to the other social insects; amongst which, if you consult my former communications, there are some exceptions to this slothful character in the males[891].
II.Age.There is less diversity in the duration of the lives of insects in their perfect than in their larva or pupastate. Some, like several species ofEphemeræ, live only a few hours; some never even see the sun[892]: others, as flies, moths, and butterflies, and indeed the majority of insects, a few days or weeks; and a comparatively small number, such as some of the largerColeoptera,Orthoptera, &c., six, nine, twelve, or fifteen months—a period beyond which the life of perfect insects rarely extends. Some, however, certainly enjoy a longer existence in the perfect state. Mr. Baker kept one of the darkling beetles (Blaps Mortisaga) alive under a glass upwards of three years. The rose-beetle (Cetonia aurata), Rösel informs us he fed with fruit and moist white bread for as long a period[893]. Esper kept our most common water-beetle (Dytiscus marginalis) in water in a large glass vessel, feeding it with meat, for three years and a half[894]. With regard to theArachnida, from the very slow growth ofScorpio europæus, Rösel suspects that it must live two or three years; and Audebert is stated to have kept a spider for several[895]. In this respect insects follow a law very different from that which obtains amongst vertebrate animals. In these the duration of their life is in proportion to the term of their growth: those which attain to maturity the latest, in almost every case living the longest. In insects, on the contrary, we often meet with the very reverse of this rule. Thus the larva of the greatgoat-moth (Cossus ligniperda) is three years, that of the cabbage-butterfly (Pieris Brassicæ) not three months, in attaining maturity; yet the perfect insects live equally long.Melolontha vulgaris, which in its first state lives four years, as a beetle lives only eight or ten days[896]. And someEphemeræ, whose larvæ have been two years in acquiring their full size, live only an hour; while the flesh-fly, whose larva has attained to maturity in three or four days, will exist several weeks.
There is yet another anomaly in the duration of the life of perfect insects. This is not, as in larger animals, a fixed period liable to be shortened only by accident or disease, and incapable of being prolonged; but an indeterminate one, whose duration is dependent on the earlier or later fulfilment of a particular animal function—that of propagation. The general law is, that a few days, or at most weeks, after the union of the sexes, both perish, the female having first deposited her eggs. If, therefore, this union takes place immediately after the disclosure of the insect from the pupa, their existence in the perfect state will not exceed a fewdaysorweeks, or in some caseshours, as in that of theEphemera, and likewise of thePhalænæ AttaciL. &c., which fall down dead immediately after oviposition[897]. But if by any means it be put off or prevented, their life may be protracted to three or four times that period. Gleditsch asserts, that by keeping apart the sexes of a grasshopper, their lives were prolonged to eight or nine weeks, instead of two or three, their ordinary length; and under similar circumstancesEphemeræ, which usually perish in a day, havebeen kept alive seven or eight. It is in consequence of this very curious fact, which has not received from physiologists the attention that it merits, that many butterflies and other insects, which, when excluded from the pupa in summer, perish in less than a month, live through the winter, if excluded late in the autumn, and the union of the sexes does not ensue. It is probable that the great age to which Baker'sBlaps, Rösel'sCetonia, and Esper'sDytiscusattained, was owing to their being virgins when taken, and subsequently kept from any sexual intercourse. A parallel case happens in the vegetable kingdom:—if annual plants are kept from seeding, they will become biennial; as, likewise, if they are sown too late in the year to produce seeds.
In the case, however, of the earlier or later exclusion of the imago, another agent has probably some influence. Buffon found that, other circumstances being alike, the silkworm-moths placed in anorthern, lived longer than those exposed to asouthernaspect: whence it appears that the stimulus of heat shortens the lives of insects, and consequently that cold tends to lengthen them.
It must be observed too, that as the death of the female insect does not take place until all the eggs are excluded, the term of her life, though usually short in the majority of species, which lay their whole number at once, is proportionably long in those which, like the queen-bee, have a longer period assigned them for this important office. Huber affirms, that he had certain proofs that she was engaged for two years in laying eggs, all impregnated by a single sexual union[898]; and in thefemales of most insects that live in society, several months are required to mature the last eggs that are in the ovary. There is one tribe of insects, however, the females of which are affirmed to survive this operation: I meanDorthesiaBosc; after which they even moult, though not so often as before[899].
I formerly related to you the singular fact, that the drones in a beehive at a certain period are without mercy slaughtered by the workers[900]. A fact the reverse of this is recorded by Morier with respect to the locusts: he affirms that the female, when she has done laying her eggs, is surrounded and killed by the males. He says that he never himself witnessed this extraordinary circumstance; but that he heard it from such authority that he gave full credit to it[901]. It is a fact, however, that seems to require further evidence to entitle it to such credit. These are instances in which, by a law of nature, the life of these insects is shortened by violence. It does not appear to have been ascertained how long those drones live that, under particular circumstances, as stated in a former letter[902], are exempted from the usual slaughter.
I am, &c.
Having shown you our little animals in every state, and traced their progress from the egg to the perfect insect, I must next give you some account of theirstructureandanatomy. And under this head I shall introduce you to a microcosm of wonders, in which the hand of anAlmightyworkman is singularly conspicuous. One would at first think that the giant bulk of the elephant, rhinoceros, or hippopotamus, must include a machine far more complicated, a skeleton more multifarious in its composition—covered by muscles infinitely more numerous—instinct with a nervous system infinitely more ramified—with a greater variety of organs and vascular systems in play, than an animal that would scarcely counterpoise a ten-millionth portion of it. Yet the reverse of this is the fact; for the Creator, the more to illustrate his wisdom, power, and skill, has decreed that the minute animals whose history we are recording, shall be much more complex in all the above respects than these mighty monarchs of the forest and the flood. Of this in the present and subsequent letters you will find repeatedand scarcely credible instances, which in every rightly constituted mind are calculated to excite, in an extraordinary degree, those sensations of reverence and love for theInvisible Authorof these wonders, and that faith and trust in his Power and Providence, which an attentive survey of the works of Creation has a natural tendency to produce. And you will not only be struck by this circumstance, but equally by the infinite variations in the structure that will present themselves to your notice; and that not sudden andper saltus, but by approaches made in the most gradual manner from one form to another. And all along, where the uses of any particular organ or part have been ascertained, if you consider its structure with due attention, you will find in it the nicest adaptation of means to an end: a circumstance this, which proves most triumphantly, that thePowerwho immediately gave being to all the animal forms, was neither a blind unconscious power, resulting from a certain order of things, as some philosophists love to speak[903]; nor a formative appetency in the animals themselves, produced by their wants, habits, and local circumstances, and giving birth, in the lapse of ages, to all the animal forms that now people our globe[904]; but a Power altogether distinct from and above nature, and itsAlmighty Author[905].
I trust that what I have here advanced will excite your attention to the subject I am now to enter upon; and I flatter myself, that although at first sight it may promise nothing more than a dry and tedious detail of parts and organs, you will find it not without its peculiar interest and attraction.
This department of the science—the Anatomy of Insects—may still be regarded as in its infancy; and consideringthe almost insuperable difficulties which, from the minuteness of the objects, oppose themselves to the skill and instruments of the entomological anatomist, we can scarcely hope that it will ever attain to that certainty and perfection to which, as far as the larger animals are concerned, anatomy has arrived. Yet infinitely more has been accomplished than might have been expected, and new accessions of light are daily thrown upon it. Whenwe consider what has been done by Malpighi, Leeuwenhoeck, and especially Swammerdam, we admire the patience, assiduity, and love of science, that enabled them, in spite of what seemed insurmountable obstacles, to ascertain, the first with respect to the silk-worm, and the latter in numerous instances, the internal organization of these minute creatures, as well as their external structure. Reaumur, and his disciple De Geer, extending their researches, have also contributed copiously to our knowledge in this branch of our science.
But in this field no one has laboured so indefatigably and with so much success as the celebrated Lyonnet; and though his attention was confined to one object—the caterpillar of the goat-moth (Cossus ligniperdaF.),—every one who studies his immortal work must admire the patient and skilful hand, the lyncean eye, and keen intellect, that discovered, denuded, and traced every organ, muscle, and fibre of that animal. Much is it to be regretted that his proposed works on the pupa and imago of the same insect, which, he informs us, were far advanced[906], were never finished and given to the world. Our regret, however, is in some degree diminished by the elaborate work of M. Herold on the butterfly of the cabbage (Pieris Brassicæ), before eulogized[907]; in which he has done much to supply this desideratum.
In more modern times, besides Herold, MM. Latreille, Illiger, Marcelle de Serres, Savigny, Ramdohr, TreviranusSprengel, Audoin, Chabrier, and, above all, M. Cuvier in his celebratedLectures on Comparative Anatomy, have considerably extended the boundaries of our knowledge in this department: and much of what I have to say to you in my letters on this subject, will be derived from these respectable sources. In the exterior anatomy of insects, I flatter myself that I shall be enabled to make some material additions to the discoveries of my predecessors; though few have occurred to me with respect to their internal organization.
In treating of the anatomy of thevertebrate animals, it is usual, I believe, to consider, first, the skeleton and its integuments, whether of skin or muscle, and their accessories; and afterwards the organs of the different vital functions and of the senses. But in considering the anatomy ofInsects, the difference before stated[908], observable between them and the sub-kingdom just mentioned, as to their structure, renders it advisable to divide this subject into two parts—the first treating of theirexternalanatomy, and the second of theirinternal.—I shall begin by drawing up for you a Table of the Nomenclature of the parts of theirexternalcrust; its appendages and processes[909], external or internal, accompanied by definitions of them; and followed by such observations respecting them as the subject may seem to require for its more full elucidation.
Anatomists have divided the human skeleton intothreegreater sections—theHead, theTrunk, and theLimbs. That of insects, likewise, is resolvable intothreeprimary sections, but without including the limbs (which, as beingappendages, and thereforesecondary, had best be considered under the section of which they form a part), for theabdomenin insects, as well as the rest of the body, being covered with acrust, and forming a distinct part, may be properly regarded as aprimarysection. And in fact these three parts may be received as primary under another view—thehead, as containing the principal organs ofsensation; thetrunk, as containing those ofmotion; and theabdomen, as containing those ofgeneration[910]. Under each of these primary sections, I shall consider its respective organs, members, and parts.
You are not to expect to find every part included in the following Table in every insect; since it has been my aim to introduce into it, the most remarkable of those that are peculiar to particular tribes, genera, &c. With respect to these, I shall generally refer you to the individuals in which they may be found.
DEFINITIONS.
Corpus(theBody). The whole crust of the insect; consisting of theExodermaor external covering, and theEsodermaor internal cuticle that lines it[911]. It is divided into three primary parts, or sections—Caput,Truncus,Abdomen.
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I. CAPUT (TheHead).
TheHeadis the anterior section of the body; consisting of a kind of box without suture or segment, which receives the organs of sensation and manducation. It includes theOs,Facies,Subfacies, andCollum.
i.Os(theMouth). That part of the head which receives and prepares the food for passing into the stomach. It includes theTrophi[912].1.Trophi(theTrophi). The different instruments or organs contained in the mouth, or closing it, and employed in manducation or deglutition. They include theLabrum,Labium,Mandibulæ,Maxillæ,Lingua, andPharynx.ALabrum(theUpper-lip). A usually moveable organ; which, terminating the face anteriorly, covers the mouth fromabove, and is situate between theMandibulæ[913]. It includes theAppendicula.aAppendicula(theAppendicle). A small piece sometimes appended to the upper-lip[914]. Ex.Halictus♀ Walck. (Melitta**. b. K.)BLabium(theUnder-lip). A moveable organ, often biarticulate, which terminating the surface anteriorly, covers the mouth frombeneath, and is situate between theMaxillæ[915]. It includes theMentum, andPalpi Labiales.aMentum(theChin). The lower joint of theLabium,where it is jointed; in other cases its base. It is usually seated between the base of theMaxillæ[916].bPalpi Labiales(theLabial Feelers). Two jointed sensiferous organs, the use of which is not clearly ascertained, which emerge, one on each side, from theLabium, mostly near its summit[917].CMandibulæ(theUpper-jaws). Two transverse lateral organs, in most insects used for manducation; generally corneous, moving horizontally, and closing the mouth above, under theLabium[918]. They include theProstheca,Dentes, andMola.aProstheca(theProstheca). A subcartilaginous process attached to the inner side, near the base, of theMandibulæof someStaphylinidæ[919]. Ex.Ocypus similisK.,Creophilus maxillosusK., &c.bDentes(theTeeth). The terminating points of theMandibulæ. They include theIncisores,Laniarii, andMolares[920].AIncisores(theCutting-teeth). Teeth somewhat wedge-shaped, externally convex and internallyconcave[921]. Ex.GryllotalpaLatr.,GryllusLatr. (AchetaF.), &c. &c.BLaniarii(theCanine-teeth). Very sharp and usually long conical teeth[922]. Ex.ForficulaL.,MantisL.,LibellulaL.CMolares(theGrinding-teeth). Teeth that terminate in a broad uneven surface, fit for grinding the food[923]. Ex. the herbivorousOrthoptera.cMola(theMola). A broad, flat, subrotund space, transversely grooved or furrowed, observable on the inner side of some mandibles that have no grinding-teeth at their apex[924]. Ex.EuchloraMacLeay,AnoplognathusLeach, Larva ofLucanus[925].DMaxillæ(theUnder-jaws). Two organs moving subhorizontally, fixed on each side at the base of theLabium, and often parallel with it—which in masticating insects seem primarily designed to hold the food[926]. They include theCardo,Stipes,Lobi, andPalpi maxillares.aCardo(theHinge). A small, transverse, usually triangular, corneous piece, upon which theMaxillacommonly sits[927].bStipes(theStalk). The corneous base of theMaxilla, below thePalpus[928].cLobi(theLobes). The parts of theMaxillaabove thePalpus[929]. They include theLobus superior, theLobus inferior, and theUngues.ALobus Superior(theUpper-lobe). The outer lobe of theMaxilla, incumbent on the inner one. In thePredaceous Beetlesthis lobe is biarticulate and palpiform[930]; and inStaphylinus olens, &c. it also consists of two joints[931]. It is called theGaleaby Fabricius, inOrthoptera, &c.[932]BLobus Inferior(theLower-lobe). The inner lobe of theMaxilla, covered by the outer one[933].CUngues(theClaws). One or more corneous sharp claws which arm the lobes of theMaxilla[934]. In thePredaceous Beetlesthere is only one terminating the lower lobe, with which, inCicindela, it articulates; in theOrthopteraandLibellulinathere are several.dPalpi Maxillares(theMaxillary Feelers). Two jointed sensiferous organs, the use of which is not clearly ascertained, emerging from an exterior lateral sinus of theMaxilla[935].ELingua(theTongue). The organ situated within theLabiumor emerging from it, by which insects in many cases collect their food and pass it down to thePharynx, situated at its roots above. It varies considerably in different orders and tribes. In theOrthoptera,Libellulina, &c. it islinguiform, and quite distinct from theLabium[936]; it appears also distinct in thelamellicornbeetles, &c.[937]In manyHymenopterait emerges from theLabium, and is fitted to collect liquids and pass them downwards[938]. InFormicait appears to be retractile[939]. In a considerable proportion of insects it seems connate with theLabium, and forming its inner surface? According to circumstances it might perhaps be denominatedLinguaorLigula. It includes theParaglossæ.aParaglossæ(theParaglossæ). Lateral and often membranous processes observable on each side of the tongue in someHymenoptera, &c.[940]FPharynx(thePharynx). The opening into the gullet[941]. It includes theEpipharynxandHypopharynx.aEpipharynx(theEpipharynx). A small valve under theLabrum, that in manyHymenopteracloses thePharynx, and is an appendage of its upper margin[942].bHypopharynx(theHypopharynx). An appendageof the lower margin of thePharynx, observable inEuceraF.[943]
i.Os(theMouth). That part of the head which receives and prepares the food for passing into the stomach. It includes theTrophi[912].
1.Trophi(theTrophi). The different instruments or organs contained in the mouth, or closing it, and employed in manducation or deglutition. They include theLabrum,Labium,Mandibulæ,Maxillæ,Lingua, andPharynx.
ALabrum(theUpper-lip). A usually moveable organ; which, terminating the face anteriorly, covers the mouth fromabove, and is situate between theMandibulæ[913]. It includes theAppendicula.
aAppendicula(theAppendicle). A small piece sometimes appended to the upper-lip[914]. Ex.Halictus♀ Walck. (Melitta**. b. K.)
BLabium(theUnder-lip). A moveable organ, often biarticulate, which terminating the surface anteriorly, covers the mouth frombeneath, and is situate between theMaxillæ[915]. It includes theMentum, andPalpi Labiales.
aMentum(theChin). The lower joint of theLabium,where it is jointed; in other cases its base. It is usually seated between the base of theMaxillæ[916].
bPalpi Labiales(theLabial Feelers). Two jointed sensiferous organs, the use of which is not clearly ascertained, which emerge, one on each side, from theLabium, mostly near its summit[917].
CMandibulæ(theUpper-jaws). Two transverse lateral organs, in most insects used for manducation; generally corneous, moving horizontally, and closing the mouth above, under theLabium[918]. They include theProstheca,Dentes, andMola.
aProstheca(theProstheca). A subcartilaginous process attached to the inner side, near the base, of theMandibulæof someStaphylinidæ[919]. Ex.Ocypus similisK.,Creophilus maxillosusK., &c.
bDentes(theTeeth). The terminating points of theMandibulæ. They include theIncisores,Laniarii, andMolares[920].
AIncisores(theCutting-teeth). Teeth somewhat wedge-shaped, externally convex and internallyconcave[921]. Ex.GryllotalpaLatr.,GryllusLatr. (AchetaF.), &c. &c.
BLaniarii(theCanine-teeth). Very sharp and usually long conical teeth[922]. Ex.ForficulaL.,MantisL.,LibellulaL.
CMolares(theGrinding-teeth). Teeth that terminate in a broad uneven surface, fit for grinding the food[923]. Ex. the herbivorousOrthoptera.
cMola(theMola). A broad, flat, subrotund space, transversely grooved or furrowed, observable on the inner side of some mandibles that have no grinding-teeth at their apex[924]. Ex.EuchloraMacLeay,AnoplognathusLeach, Larva ofLucanus[925].
DMaxillæ(theUnder-jaws). Two organs moving subhorizontally, fixed on each side at the base of theLabium, and often parallel with it—which in masticating insects seem primarily designed to hold the food[926]. They include theCardo,Stipes,Lobi, andPalpi maxillares.
aCardo(theHinge). A small, transverse, usually triangular, corneous piece, upon which theMaxillacommonly sits[927].
bStipes(theStalk). The corneous base of theMaxilla, below thePalpus[928].
cLobi(theLobes). The parts of theMaxillaabove thePalpus[929]. They include theLobus superior, theLobus inferior, and theUngues.
ALobus Superior(theUpper-lobe). The outer lobe of theMaxilla, incumbent on the inner one. In thePredaceous Beetlesthis lobe is biarticulate and palpiform[930]; and inStaphylinus olens, &c. it also consists of two joints[931]. It is called theGaleaby Fabricius, inOrthoptera, &c.[932]
BLobus Inferior(theLower-lobe). The inner lobe of theMaxilla, covered by the outer one[933].
CUngues(theClaws). One or more corneous sharp claws which arm the lobes of theMaxilla[934]. In thePredaceous Beetlesthere is only one terminating the lower lobe, with which, inCicindela, it articulates; in theOrthopteraandLibellulinathere are several.
dPalpi Maxillares(theMaxillary Feelers). Two jointed sensiferous organs, the use of which is not clearly ascertained, emerging from an exterior lateral sinus of theMaxilla[935].
ELingua(theTongue). The organ situated within theLabiumor emerging from it, by which insects in many cases collect their food and pass it down to thePharynx, situated at its roots above. It varies considerably in different orders and tribes. In theOrthoptera,Libellulina, &c. it islinguiform, and quite distinct from theLabium[936]; it appears also distinct in thelamellicornbeetles, &c.[937]In manyHymenopterait emerges from theLabium, and is fitted to collect liquids and pass them downwards[938]. InFormicait appears to be retractile[939]. In a considerable proportion of insects it seems connate with theLabium, and forming its inner surface? According to circumstances it might perhaps be denominatedLinguaorLigula. It includes theParaglossæ.
aParaglossæ(theParaglossæ). Lateral and often membranous processes observable on each side of the tongue in someHymenoptera, &c.[940]
FPharynx(thePharynx). The opening into the gullet[941]. It includes theEpipharynxandHypopharynx.
aEpipharynx(theEpipharynx). A small valve under theLabrum, that in manyHymenopteracloses thePharynx, and is an appendage of its upper margin[942].
bHypopharynx(theHypopharynx). An appendageof the lower margin of thePharynx, observable inEuceraF.[943]
Thesevenorgans of the mouth above defined, viz.theLabrum, Labium,the twoMandibulæ,the twoMaxillæ,and theLingua,constitute what may be denominated aperfectmouth, peculiar to those insects thatmasticatetheir food[944].In those that take it bysuction,theTrophi,to adapt them for that purpose, assume a variety of forms, and should be distinguished by as many appellations. In almost every case, however, therudimentsorrepresentativesof the above organs have been detected by the elaborate researches of that learned and able zoologist, M. Savigny[945].I shall next subjoin definitions of the principal kinds of suctorious mouths.
2.Promuscis(thePromuscis). The oral instrument ofHemiptera, in which the ordinaryTrophiare replaced[946]by a jointed sheath, covered above at the base by theLabrum, withoutLabella(Liplets) at the end, and containing four long capillary lancets, and a short tongue[947]. It includes theVagina, andScalpella.AVagina(theVagina). The jointed sheath of thePromuscis, representing theLabiumin aperfectmouth[948].BScalpella(theLancets). Four pieces adapted for perforating the food of the insect, which when united form a tube for suction. The upper pair represent theManidibulæ[949], and the lower theMaxillæ[950].3.Proboscis(theProboscis). The oral instrument ofDiptera, in which the ordinaryTrophiare replaced by an exarticulate sheath, terminated byLabella, and containing one or more lancets covered by a valve[951]. It includes theTheca, andHaustellum.ATheca(theTheca). The sheath or case of theProboscis, representing theLabiumin aperfectmouth[952]. It includes theBasis, andLabella.aBasis(theBase). The whole lower part of theTheca, from the mouth of the insect as far as theLabella, probably to be regarded as representing theMentum?bLabella(theLiplets). A pair of tumid lobes, often corrugated and capable of tension and relaxation, which terminate theTheca, and perhaps represent the termination of theLabium[954]?BHaustellum(theHaustellum). The instrument of suction contained in theTheca[955]. It includes theValvula,Cultelli, andScalpella.aValvula(theValvule). A corneous piece which covers the instruments of suction above, representing theLabrumin a perfect mouth[956].bCultelli(theKnives). The upper pair of the instruments of suction, which probably make the first incision in the food of the insect; they represent theMandibulæof the perfect mouth[957].cScalpella(theLancets). A pair of instruments, usually more slender than theCultelli, which probably enter the veins or sap-vessels, and together with them form a tube for suction[958].4.Antlia(theAntlia). The oral instrument ofLepidoptera, in which the ordinaryTrophiare replaced by a spiral, bipartite, tubular machine for suction, with its appendages[959]. It includes theSolenaria, andFistula.ASolenaria(theSolenaria). The two lateral subcylindrical air-tubes of theAntlia[960].BFistula(theFistula). The intermediate subquadrangular pipe, formed by the union of the two branches of theAntlia, which conveys the nectar to thePharynx[961]. These two branches represent theMaxillæof the perfect mouth.—N. B. M. Savignydiscovered the rudiments of the remainingTrophiin this kind of mouth[962].5.Rostrulum(theRostrulum). The oral instrumentofAphaniptera(PulexL.), in which the ordinaryTrophiare replaced by a bivalve beak, between the valves of which there appear to be three lancets[963]. It includes theLaminæ,Scalpella, andLigula.ALaminæ(theLaminæ). Two corneous plates which are laterally affixed to the mouth of a flea, probably representing theMandibulæof the perfect mouth, which somewhat resemble the beak of a bird[964].BScalpella(theLancets). The two upper or outer instruments, probably for making an incision in the skin; these are flat and acute, and seem to represent theMaxillæof the perfect mouth[965].CLigula(theLigula). A capillary instrument between the lancets; probably representing thetongueof the perfect mouth[966].6.Rostellum(theRostellum). The oral instruments ofPediculusand some otherAptera, in which the ordinaryTrophiare replaced by an exarticulate retractile tube, which exerts a retractile siphuncle. It includes theTubulusandSiphunculus.ATubulus(theTubulet). The tube or retractile base of theRostellum.BSiphunculus(theSiphuncle). The real instrument of suction, which when unemployed is retracted within the tubulet.
2.Promuscis(thePromuscis). The oral instrument ofHemiptera, in which the ordinaryTrophiare replaced[946]by a jointed sheath, covered above at the base by theLabrum, withoutLabella(Liplets) at the end, and containing four long capillary lancets, and a short tongue[947]. It includes theVagina, andScalpella.
AVagina(theVagina). The jointed sheath of thePromuscis, representing theLabiumin aperfectmouth[948].
BScalpella(theLancets). Four pieces adapted for perforating the food of the insect, which when united form a tube for suction. The upper pair represent theManidibulæ[949], and the lower theMaxillæ[950].
3.Proboscis(theProboscis). The oral instrument ofDiptera, in which the ordinaryTrophiare replaced by an exarticulate sheath, terminated byLabella, and containing one or more lancets covered by a valve[951]. It includes theTheca, andHaustellum.
ATheca(theTheca). The sheath or case of theProboscis, representing theLabiumin aperfectmouth[952]. It includes theBasis, andLabella.
aBasis(theBase). The whole lower part of theTheca, from the mouth of the insect as far as theLabella, probably to be regarded as representing theMentum?
bLabella(theLiplets). A pair of tumid lobes, often corrugated and capable of tension and relaxation, which terminate theTheca, and perhaps represent the termination of theLabium[954]?
BHaustellum(theHaustellum). The instrument of suction contained in theTheca[955]. It includes theValvula,Cultelli, andScalpella.
aValvula(theValvule). A corneous piece which covers the instruments of suction above, representing theLabrumin a perfect mouth[956].
bCultelli(theKnives). The upper pair of the instruments of suction, which probably make the first incision in the food of the insect; they represent theMandibulæof the perfect mouth[957].
cScalpella(theLancets). A pair of instruments, usually more slender than theCultelli, which probably enter the veins or sap-vessels, and together with them form a tube for suction[958].
4.Antlia(theAntlia). The oral instrument ofLepidoptera, in which the ordinaryTrophiare replaced by a spiral, bipartite, tubular machine for suction, with its appendages[959]. It includes theSolenaria, andFistula.
ASolenaria(theSolenaria). The two lateral subcylindrical air-tubes of theAntlia[960].
BFistula(theFistula). The intermediate subquadrangular pipe, formed by the union of the two branches of theAntlia, which conveys the nectar to thePharynx[961]. These two branches represent theMaxillæof the perfect mouth.—N. B. M. Savignydiscovered the rudiments of the remainingTrophiin this kind of mouth[962].
5.Rostrulum(theRostrulum). The oral instrumentofAphaniptera(PulexL.), in which the ordinaryTrophiare replaced by a bivalve beak, between the valves of which there appear to be three lancets[963]. It includes theLaminæ,Scalpella, andLigula.
ALaminæ(theLaminæ). Two corneous plates which are laterally affixed to the mouth of a flea, probably representing theMandibulæof the perfect mouth, which somewhat resemble the beak of a bird[964].
BScalpella(theLancets). The two upper or outer instruments, probably for making an incision in the skin; these are flat and acute, and seem to represent theMaxillæof the perfect mouth[965].
CLigula(theLigula). A capillary instrument between the lancets; probably representing thetongueof the perfect mouth[966].
6.Rostellum(theRostellum). The oral instruments ofPediculusand some otherAptera, in which the ordinaryTrophiare replaced by an exarticulate retractile tube, which exerts a retractile siphuncle. It includes theTubulusandSiphunculus.
ATubulus(theTubulet). The tube or retractile base of theRostellum.
BSiphunculus(theSiphuncle). The real instrument of suction, which when unemployed is retracted within the tubulet.
Besides the above variations from the type of what I call aPerfect Mouth,there are others in which the parts of theTrunkappear to aid in the conversion of the food,and become a kind of accessoryLabium, Maxilla, &c.Thus in theMyriapods,the anterior pair of legs assume aMaxillaryform and office[967];theProsternumthose of aLabium[968]:in theArachnida,also, the anteriorCoxæare accessoryMaxillæ.In thisClass,likewise, as has been more than once observed[969],the representatives of the interior pair ofAntennæof theCrustacea,are thought to assume the form and the functions of suctoriousMandibles[970].
ii.Facies(theFace). The upper surface of the head[971]. It includes all the parts that lie between its junction with theProthoraxand theLabrum: viz.Nasus,Postnasus,Frons,Vertex,Occiput,Genæ,Tempora,Oculi,Stemmata, andAntennæ.1.Nasus(theNose). That portion of the face, often elevated and remarkable, situated between theLabrum,Postnasus, andGenæ, and with which theLabrumarticulates; called by Fabricius theClypeus[972]. It includes theRhinarium.ARhinarium(theNostril-piece). The space between the anterior margin of theNasusand theLabrum, in which, in vertebrate animals, the nostrils are often situated[973].—N. B.This is remarkable in some Lamellicorn beetles, asAnoplognathusLeach.InNecrophorus,and some others, it is membranous.2.Postnasus(thePostnasus). That part of theFaceimmediately contiguous to theAntennæ, that liesbehind theNasus, when distinctly marked out.—Ex.Sagra,Prosopis.3.Frons(theFront). That part of theFacewhich lies behind thePostnasus, and usually between the posterior part of the eyes. This is sometimes the region of theStemmata; or they are partly in this or partly in theVertex[974].4.Vertex(theVertex). The horizontal part of theFacies, next the front, that lies behind the eyes and between the temples[975]. This also is often the region of theStemmata.5.Occiput(theOcciput). The back part of the head when it is vertical, or nearly so, to its point of junction with the trunk[976].—Ex.Meloe,Ripiphorus,Hymenoptera,Diptera.6.Genæ(theCheeks). Those parts which lie on the outside of the anterior half of the eyes, and intervene also between them and theMandibulæ[977].7.Tempora(theTemples). Those parts which lie on the outside of the posterior half of the eyes, between which theFronsandVertexintervene[978].8.Oculi(theEyes). The principal organs of sight, most commonly two in number, placed in the sides of the head. In the majority they are compound, consisting of hexagonal lenses. In theArachnidathey are simple[979].ACanthus(theCanthus). A process of the face, which enters the notch or sinus of the eye[980].—Ex.ScarabæusL.,CerambyxL.9.Stemmata(theEyelets). Two, or more commonlythree, convex, crystalline, simple eyes, observable in theFronsorVertex, or common to both[981].—Ex.Orthoptera,Hemiptera,Hymenoptera.10.Antennæ(theAntennæ). Two moveable and jointed sensiferous organs, situated in the space between or before the eyes, but in no instance behind them[982]. They include theTorulus,Scapus,Pedicellus, andClavola.ATorulus(theBed). The cavity or socket in which the base of theAntennais planted[983].BScapus(theScape). The first and in many cases the most conspicuous joint of theAntennæ[984]. It includes theBulbus.aBulbus(theBulb). The base of theScapus, by which it inosculates in theTorulus, often subglobose, and looking like a distinct joint[985]. It acts the part of aRotula, being the pivot upon which theAntennaturns.CPedicellus(thePedicel). The second joint of theAntenna[986]: in some insects acting also the part of aRotulain the socket of theScapus, to give separate motion to theClavola.DClavola(theClavolet). The remaining joints of theAntennataken together[987]. It includes theCapitulum.aCapitulum(theKnob). The last joints of theClavolawhen suddenly larger than the rest[988].iii.Subfacies(theSubface). The lower surface or underside of the head[989]. It includes theLoraandJugulum.1.Lora(theLora). A corneous angular machine observable in the mouth of some insects, upon the intermediate angle of which theMentumsits, and on the lateral ones theCardinesof theMaxillæ; and by means of which theTrophiare pushed forth or retracted[990].—Ex.Hymenoptera.2.Jugulum(theThroat). That part of the subface that lies between the temples[991].iv.Collum(theNeck). The constricted posterior part of a pedunculate head, by which it inosculates in the trunk[992]. It includes theNucha,Gula, andMyoglyphides.1.Nucha(theNape). The upper part of the neck[993]. It includes theMyoglyphides.AMyoglyphides(theMuscle-notches). Notches in the posterior margin of the neck, usually two in number, observable in Coleopterous insects, to which the levator muscles are attached[994].2.Gula(theGula). The lower part of the neck[995].v.Cephalophragma(theCephalophragm). A Y-shaped partition that divides the head internally inLocustaLeach, into two chambers, an anterior and posterior.
ii.Facies(theFace). The upper surface of the head[971]. It includes all the parts that lie between its junction with theProthoraxand theLabrum: viz.Nasus,Postnasus,Frons,Vertex,Occiput,Genæ,Tempora,Oculi,Stemmata, andAntennæ.
1.Nasus(theNose). That portion of the face, often elevated and remarkable, situated between theLabrum,Postnasus, andGenæ, and with which theLabrumarticulates; called by Fabricius theClypeus[972]. It includes theRhinarium.
ARhinarium(theNostril-piece). The space between the anterior margin of theNasusand theLabrum, in which, in vertebrate animals, the nostrils are often situated[973].—N. B.This is remarkable in some Lamellicorn beetles, asAnoplognathusLeach.InNecrophorus,and some others, it is membranous.
2.Postnasus(thePostnasus). That part of theFaceimmediately contiguous to theAntennæ, that liesbehind theNasus, when distinctly marked out.—Ex.Sagra,Prosopis.
3.Frons(theFront). That part of theFacewhich lies behind thePostnasus, and usually between the posterior part of the eyes. This is sometimes the region of theStemmata; or they are partly in this or partly in theVertex[974].
4.Vertex(theVertex). The horizontal part of theFacies, next the front, that lies behind the eyes and between the temples[975]. This also is often the region of theStemmata.
5.Occiput(theOcciput). The back part of the head when it is vertical, or nearly so, to its point of junction with the trunk[976].—Ex.Meloe,Ripiphorus,Hymenoptera,Diptera.
6.Genæ(theCheeks). Those parts which lie on the outside of the anterior half of the eyes, and intervene also between them and theMandibulæ[977].
7.Tempora(theTemples). Those parts which lie on the outside of the posterior half of the eyes, between which theFronsandVertexintervene[978].
8.Oculi(theEyes). The principal organs of sight, most commonly two in number, placed in the sides of the head. In the majority they are compound, consisting of hexagonal lenses. In theArachnidathey are simple[979].
ACanthus(theCanthus). A process of the face, which enters the notch or sinus of the eye[980].—Ex.ScarabæusL.,CerambyxL.
9.Stemmata(theEyelets). Two, or more commonlythree, convex, crystalline, simple eyes, observable in theFronsorVertex, or common to both[981].—Ex.Orthoptera,Hemiptera,Hymenoptera.
10.Antennæ(theAntennæ). Two moveable and jointed sensiferous organs, situated in the space between or before the eyes, but in no instance behind them[982]. They include theTorulus,Scapus,Pedicellus, andClavola.
ATorulus(theBed). The cavity or socket in which the base of theAntennais planted[983].
BScapus(theScape). The first and in many cases the most conspicuous joint of theAntennæ[984]. It includes theBulbus.
aBulbus(theBulb). The base of theScapus, by which it inosculates in theTorulus, often subglobose, and looking like a distinct joint[985]. It acts the part of aRotula, being the pivot upon which theAntennaturns.
CPedicellus(thePedicel). The second joint of theAntenna[986]: in some insects acting also the part of aRotulain the socket of theScapus, to give separate motion to theClavola.
DClavola(theClavolet). The remaining joints of theAntennataken together[987]. It includes theCapitulum.
aCapitulum(theKnob). The last joints of theClavolawhen suddenly larger than the rest[988].
iii.Subfacies(theSubface). The lower surface or underside of the head[989]. It includes theLoraandJugulum.
1.Lora(theLora). A corneous angular machine observable in the mouth of some insects, upon the intermediate angle of which theMentumsits, and on the lateral ones theCardinesof theMaxillæ; and by means of which theTrophiare pushed forth or retracted[990].—Ex.Hymenoptera.
2.Jugulum(theThroat). That part of the subface that lies between the temples[991].
iv.Collum(theNeck). The constricted posterior part of a pedunculate head, by which it inosculates in the trunk[992]. It includes theNucha,Gula, andMyoglyphides.
1.Nucha(theNape). The upper part of the neck[993]. It includes theMyoglyphides.
AMyoglyphides(theMuscle-notches). Notches in the posterior margin of the neck, usually two in number, observable in Coleopterous insects, to which the levator muscles are attached[994].
2.Gula(theGula). The lower part of the neck[995].
v.Cephalophragma(theCephalophragm). A Y-shaped partition that divides the head internally inLocustaLeach, into two chambers, an anterior and posterior.
II. TRUNCUS (TheTrunk).
TheTrunkis the intermediate section of the body, which lies between theHeadand theAbdomen[996]. It includes theManitruncus, and theAlitruncus[997].