ENTOMOLOGY

E N T O M O L O G Y.

ENTOMOLOGY, the science of insects, or that part of zoology which treats of insects.

Whoever is desirous of attaining a systematic knowledge of insects, ought primarily to be solicitous about acquiring the terms made use of in the science, that so he may be able rightly to denominate every part of an insect. The student is first to know what an insect is, lest he mistake hippocampi, and other amphibious animals, for them, as was formerly done; or confound them with the vermes, which Linnaeus first distinguished from insects, and which differ as essentially from them as the class mammalia do from birds. Every insect is furnished with a head, antennæ, and feet, of all which the vermes are destitute. All insects have six or more feet; they respire through pores placed on the

sides of their bodies, and which are termed spiracula; their skin is externally hard, and serves them instead of bones, of which they have internally none. From this definition, the acus marina is evidently no insect. But the antennæ placed on the fore-part of the head, constitute the principal distinction. These are jointed and moveable in every part, in which they differ from the horns of other animals: they are organs conveying some kind of sense; but we have no more idea of what this kind of sense is, than a man has, who, without eyes, attempts to determine the particular action of the rays of light on the retina of the eye, or to explain the changes which from thence take place in the human mind. That they are the organs of some kind of sense, is apparent from their perpetually moving them

them forward; yet the hard crust with which they are invested, and their shortness in flies and other insects, would induce one to believe them not to be the organs of touch: Mr Barbut supposes them to constitute or to contain the organs of hearing. That they are tubular, and filled with air, and some kind of humour, appears from the antennæ of butterflies immersed in water.—To come now to the terms of the art. A knowledge of the external parts of the body is first to be established; which, after the method of anatomists, we divide into head, trunk, abdomen, and extremities.

SECT. I. External parts of the Body.

I. CAPUT, the HEAD. This part in insects without brain. The difference between the brain and spinal marrow consists in the former being a medullary part organized. We do not deny the existence of a medullary thread in the heads of insects, but we never could discover it to be organized: hence the hippobosca equina, or horse-fly, will live, run, nay even copulate, after being deprived of its head; to say nothing of many others which are capable of living a long while in the same situation.

As they are not apparently furnished with ears, they have been apprehended incapable of hearing; as we can no more conceive that sense to exist without ears, than vision without eyes. That they are nevertheless susceptible of any shrill or loud noise, as well as fishes, is indisputable; but it has been supposed to be in a manner different from that of hearing. Mr Barbut, however, supposes them to possess this sense in a very distinct manner. Many insects, he observes, are well known to be endowed with the power of uttering sounds, such as large beetles, the bee, wasp, common fly, gnat, &c. The sphinx atropos squeaks, when hurt, nearly as loud as a mouse. Now, if insects are endowed with the power of uttering sounds, it certainly must be for some purpose. As they vary their cry occasionally, it must certainly be designed either to give notice of pleasure or pain, or some affection in the creature who possesses it. "The knowledge of their sounds (says our author) is undoubtedly confined to their tribe, and is a language intelligible to them only; saving when violence obliges the animal to exert the voice of nature in distress, craving compassion; then all animals understand the doleful cry. For instance, attack a bee or wasp near the hive or nest, or a few of them: the consequence of that assault will be, the animal or animals, by a different tone of voice, will express his or their disapprobation or pain; that sound is known to the hive to be plaintive, and that their brother or brethren require their assistance; and the offending party seldom escapes with impunity. Now, if they had not the sense of hearing, they could not have known the danger their brother or brethren were in by the alteration of their tone."

Another proof, which he reckons still more decisive, was taken from an observation made by himself a large spider in St James's park. This creature had made a very large web on a wooden railing; and was, at the time of observation, on one of the rails at a considerable distance from the place where a large fly entangled itself. Nevertheless, the moment the fly was entangled, the spider became sensible of it; though,

from the situation of the rail, he could not possibly have seen it. In this, however, Mr Barbut might possibly be deceived; because the spider was perhaps alarmed by the tremulous motion of the threads, occasioned by the fluttering of the fly; which he might well know how to distinguish from their vibration by the wind. The organ of hearing, in our author's opinion, is situated in the antennæ; both from their situation in the part of the head most favourable to such organs, their inward structure being moveable, the ears of most inferior animals being so. He has never considered the antennæ as either offensive or defensive, but has observed them to be endowed with an exquisite sense of feeling; that the animal appeared to be in agony when its antennæ were pinched; and that it takes care to avoid the touching any hard substance with them roughly. "This tenderness in the organ of hearing (says he) is common to all animals; and insects seem to be particularly tender in these parts by quickly withdrawing them from the touch."

Our author further observes, that the antennæ of all insects are composed of joints varying in size, form, and number. Those who are chiefly confined to live under water have their antennæ in general shorter than those who live on land. Some who roam at large in the air, have them long and slender. They are all hollow, and are rendered flexible by the joints, which are very visible in the horns of the crab and lobster. This hollowness, in our author's opinion, is to receive the sound communicated to the extremities of the antennæ by the repercussion of the air affected by any noise, and convey it, by means of the joints, from one to another, till it arrives in that lessened degree of tone best suited to the timid nature of the animal. In this circumstance there may be many variations in point of perfection in those organs: the strength, utility, and degree of power in receiving sound being proportioned to the necessities of the animals, different in their nature and requisites. In most animals, the entrance to the auricular organ is patulous; but in this case the animal would suffer great inconvenience from such an organisation, as the organ would often be clogged with dirt, &c.

It has also appeared dubious if they have the sense of smell, no organ being found in them adapted to that purpose: and although it was evident they had a perception of agreeable and fetid effluvia, it was thought to be in a manner altogether unknown to us. Mr Barbut is of opinion that the organs of smell reside in the palpi or feelers. Many insects have four and some six, two of which are in general cheliform, in order to assist the insect in conveying its food to its mouth. It may be likewise observed, that the palpi are in continual motion; the animal thrusting them into every kind of putrid or other matter, as a hog would do his nose, smelling and searching after food. Insects which apparently do not possess palpi or spiral tongues, have undoubtedly some organ concealed within the mouth analogous to them in function and utility; the fleshy proboscis of the fly is thrust into every substance in which the animal expects to find food; and when it is extended, nearly in the middle are situated, in our author's opinion, two upright palpi, which, no doubt, perform in their turn some office, perhaps that of smell.

Many insects have no tongue, nor make any sound with their mouth; but for this purpose some use their feet, others their wings, and others some elastic instrument with which they are naturally furnished.

EYES. Most insects have two; but the gyrrinus has four, the scorpion six, the spider eight, and the scelopendra three. They have no eye-brows, but the external tunic of their eyes is hard and transparent like a watch-glass; their eyes have no external motion, unless it be in the crab. They consist for the most part of one lens only; but in those of the butterfly, diptera, and many of the beetles, they are more numerous. Pugett discovered 17,325 lenses in the cornea of a butterfly, and Lieuwenhoek 800 in a fly.

ANTENNE. Of these there are in general two (unless four are allowed to some kind of crabs), and placed on the fore-part of the head: they are peculiar to insects; and are plainly distinguishable from the tentaculæ of the vermes, in being crustaceous; and from the palpi of insects, which are more numerous, placed near the mouth, and are sometimes wanting. As the antennæ are of great moment in distinguishing the various kinds of insects, we shall enumerate and explain the several different forms of them.

Setacea, are those which grow gradually taper towards the extremity.

Filiformes, such as are of the same thickness throughout.

Moniliformes, are filiform, like the preceding, but consist of a series of round knobs, like a necklace of beads.

Clavata, such as gradually increase in size toward the extremity.

Capitata, are clavata, but have the extremity somewhat round.

Fissiles, are capitata; but have the capitulum, or knob, divided longitudinally into three or four parts, or laminae, as in the scarabæi.

Perfoliata, are also capitata; but have the capitulum horizontally divided, as in the dermelites.

Pectinate, so called from their similitude to a comb, tho' they more properly resemble a feather, as in the moths and elateres. This is most obvious in the male.

Aristata, such as have a lateral hair, which is either naked or furnished with lesser hairs, as in the fly: Breviores, those which are shorter than the body; longiores, those which are longer than the body; mediocres, those which are of the same length with the body; all three of which varieties are distinguishable in the cerambyces.

PALPI, or Feelers, resemble filiform, articulated, moveable antennæ. They are most commonly four in number, sometimes six; they are sufficiently distinguished from antennæ, in being naked, short, and always placed at the mouth.

OS, the Mouth, is generally placed in the anterior part of the head, extending somewhat downwards. In some insects, it is placed under the breast, as in the chermes, coccus, cancer (crab), and curculio.

ROSTRUM, or Proboscis, is the mouth drawn out to a rigid point: in many of the hemiptera class it is bent downward toward the breast and belly, as in the cicada, nepa, notonecia, cimex (bug), aphid, and remarkably so in some curculiones.

MAXILLÆ, the Jaws, are two in number, sometimes

four, and at other times more; they are placed horizontally; the inner edge of them in some insects is serrated, or furnished with little teeth.

LINGUA, the Tongue, in some insects is taper and spiral, as in the butterfly; in others it is fleshy, resembling a proboscis, and tubular, as in the fly.

LABIUM SUPERIUS, the upper Lip, is situated above the jaws; as in the scarabæus and gryllus.

STEMMATA, or Crown, are three smooth hemispheric dots, placed generally on the top of the head; as in most of the hymenoptera, and others.

II. TRUNCUS, the TRUNK, is that part which comprehends the breast or thorax: it is situated between the head and abdomen; and has the legs inserted into it, that its parts may be distinctly determined. It is divided into thorax, scutellum, and sternum.

THORAX, the Thorax, is the back part of the breast; and is very various in its shape. It is called dentatus, when its sides are armed with points; spinatus, when its back is furnished with them, as in the cerambyx; and marginatus, when its margin is laterally dilated, as in the silpha and coccids.

SCUTELLUM, or Escutcheon, is the posterior part of the thorax: it is frequently triangular; and appears to be divided from the thorax by an intervening suture, as in most of the coleoptera.

STERNUM, the Sternum, is situated on the inferior part of the thorax; it is pointed behind in the elateres, and bifid in some of the dytiscids.

III. ABDOMEN, the ABDOMEN is in most insects distinct from the thorax; it is the posterior part of the body of the insect; and is composed of a number of annular segments, which serve occasionally to lengthen or shorten it, and to contain the organs of chylification, &c.

SIRACULA, are little holes or pores, placed singly on each side of every segment of the abdomen: thro' these the insect breathes; and if oil be applied so as to stop them up, it proves fatal to most of them.

TERGUM, the Back, is the superior part of the abdomen.

VENTER, the Belly, is the inferior part.

ANUS, is the posterior part of the abdomen, perforated for the evacuation of the excrement. This part also frequently contains the organs of generation.

IV. ARTUS, the LIMBS or EXTREMITIES, are the various instruments of motion.

PEDES, the Legs, are generally six. There is an exception to this, however, in the class Aptera, many of which have eight; as acari (mites), phalangii, most of the aranei, (spiders) scorpiones, (scorpions) and cancri (crabs.) The oniscus has 14, and the luli and scelopendri still more.

The first joint of the leg, which is generally thickest, is called semitur; the second, which is generally of the same size throughout, tibia; the third, which is jointed, is distinguished by the name of tarsus; and the last, which in most insects is double, by that of unguis. The legs of insects, in general, are named from the various motions they produce: Cursores, from that of running, which are the most numerous;

&c. saltatorii, from that of leaping; natatorii, from that of swimming, &c.—In the saltatorii, the thighs are remarkably large, by which means they are able to leap to a considerable distance, as in the gryllus, (grasshopper), &c. In those of the Natatorii, the feet are flat, and edged with hairs, which answer the purpose of oars in assisting them to swim, as in the dytiscus.—Mutici, are such feet as have no claws.—Chelæ, or claws, are the fore-feet enlarged towards their extremities, each of which is furnished with two lesser claws, which act like a thumb and finger; as in the crab.

ALÆ, Wings, the instruments which enable them to fly. These are membranous, and undivided, except in the instance of the phalæne alucitæ, in which they are in part divided. Most insects have four; the diptera-class, and the coccus, however, have two only.

The wing is divided into its superior and inferior surfaces: its anterior part in a butterfly, is that towards the anterior margin, or next to the head; its posterior part, that towards the anus; its exterior part, that towards the outer edge; and the interior, that next the abdomen.

They are called plicatiles, when they are folded at the time the insect is at rest, as in the wasp; opposite to these are the planæ, which are incapable of being folded.

Erectæ, such as have their superior surfaces brought in contact when the insect is at rest; as in the ephemeræ, libellula puella and virgo, and papiliones (butterflies.)

Patentes, which remain horizontally extended when the insect is at rest; as in the phalæne geometræ, and most of the libellulæ.

Incumbentes, such as cover horizontally the superior part of the abdomen when the insect is at rest.

Deflexæ, are incumbentes, but not horizontally, the outer edges declining toward the sides.

Reversæ, are deflexæ, with this addition, that the edge of the inferior wings projects from under the anterior part of the superior ones.

Dentatæ, in which the edge is serrated, or scolloped.

Caudatæ, in which one or more projections in the hinder wings are extended into processes.

Reticulatæ, when the vessels of the wings put on the appearance of network, as in the hemerobius perla; the two anterior wings generally become superior, and the posterior ones inferior, in moths, when their wings are closed; but the anterior wings are called primary, and the inferior ones secondary, in butterflies, as they cannot with propriety be called inferior when the wings are erect.

Colores, the colours, these are self-apparent: but according to their several shapes, they take the different names of punctæ, dots; maculæ, spots; fasciæ, bands, which frequently run across and sometimes surround the edge of the wings; Strigæ, streaks, which are very slender fasciæ; and lineæ, lines, which are longitudinally extended.

Ocellus, is a round spot, containing a lesser spot of a different colour in its centre.

Stigmata, another term lately introduced by Linnaeus, signifies the spot, or anastomosis, in the middle

of the wing near the anterior margin; it is conspicuous in most of the hymenoptera and neuroptera, and even in the coleoptera. The single or double kidney-shaped spot, situated in the same part of the anterior wings, and frequently occurring in the phalæne paganae, is distinguished likewise by the name of stigma.

Elytra (in the singular number elytron.) The upper wings, which are of a hard substance, in some degree resembling leather, and which in most insects are of a very hard texture, but in others flexible, are called elytra; their superior surface is generally convex, their inferior one concave. When the insect flies, they are extended; and shut when it rests, closing together, and forming a longitudinal suture down the middle of the back, as in the coleoptera.

They are of various shapes. Abbreviata, when shorter than the abdomen. Truncata, when shorter than the abdomen, and terminating in a transverse line. Pastigiata, when of equal or greater length than the abdomen, and terminating in a transverse line. Serrata, when the exterior margin towards the apex is notched or serrated, as in some of the buprestes. Spinosa, when their surface is covered with sharp points or prickles. Scabra, when their surface is so uneven as to grate against the fingers. Striata, when marked with slender longitudinal furrows. Porcata, when with elevated longitudinal sulci or ridges. Sulcata, when these ridges are concave. Hemelytra, when the superior wings are of a middle substance betwixt leather and membrane; either totally so, as in the grylli; or partially so, as in the cimices, nepræ, and notonectæ: These are commonly distinguished by the name hemiptera.

Halteres, poisers, (a term also introduced by Linnaeus), are little heads placed on a stalk or peduncle, most frequently under a little arched scale. They are found only in the class diptera, and appear to be nothing more than the rudiments of the hinder wings.

CAUDA, the Tail, in most insects is,

Simplex, simple, capable of being extended, and again drawn back at pleasure. In the crab and scorpion, however, it is

Elongata, elongated, or lengthened out.

Setacea, bristle-shaped, or taper; as in the raphidia.

Trifida, consisting of three bristles; as in the ephemeræ.

Forcata, being forked, as in the podura.

Forcipata, resembling a pair of forceps; as in the forficula.

Foliosa, resembling a leaf; as in the blatta, grylli, and some species of canceri.

Telifera, such as are armed with a dart or sting; as in the scorpion and panorpa.

Aculeus, an instrument with which they wound, and at the same time instill a poison; with such the bee, wasp, scorpion, &c. are furnished.

EXPLANATION of PLATE CCCXVIII. upper Compartment.

Fig. 1. ANTENNÆ PECTINATÆ, or feather'd; as in the phalæne, moths.

2. ———— PERSOLIATÆ, or persoliated; as in the dermestes and dytiscus.

3. ———— FISSILES, or fissile, divided into laminae

minæ at the extremity, as in the scarabæi, beetles.

1. 4. ANTENNÆ CLAVATÆ, or club-shaped, as in the papilio, butterfly.
2. 5. ——— MONILIFORMES, like a necklace of beads; as in the chrysomela.
3. 6. ——— SETACEÆ, setaceous, or bristle-shaped; as in many of the phalene.
4. 7. ——— ARISTATÆ, furnished with a lateral hair, as in the fly.
5. 8. 9. a Caput, the head.
6. b Palpi, or feelers.
7. c Antennæ, or horns.
8. d Oculi, the eyes.
9. e Thorax.
10. f Scutellum, or escutcheon.
11. g Pectus, or breast.
12. h Sternum, or breast-bone.
13. i Abdomen, and its segments.
14. k Anus.
15. l Elytra, or shells.
16. m Membranous wings.
17. n Pedes, or feet, which are natatorii.
18. 10. o Femur, or thigh.
19. p Tibia, or leg.
20. q Tarsus, or foot.
21. r Unguis, or claw.
22. 11. a The anterior part of the wing.
23. b The posterior part.
24. c The exterior part.
25. d The interior part.
26. e The margin.
27. f The disk, or middle.
28. g Oculus, or eye.
29. 12, 13, 14, 15. Represent the insect in its egg, caterpillar, pupa, and perfect state.

SECT. II. Of the SEXES of INSECTS.

THE same difference of sex exists in insects as in other animals, and they even appear more disposed to increase their species than other animals; many of them, when become perfect, seeming to be created for no other purpose but to propagate their species. Thus the silk-worm, when it arrives at its perfect or moth-state, is incapable of eating, and can hardly fly: it endeavours only to propagate its species; after which the male immediately dies, and the female as soon as she has deposited her eggs.

In many insects, the male and female are with difficulty distinguished; and in some they differ so widely, that an unskilful person might easily take the male and female of the same insect for different species; as for instance, in the phalæna humuli, piniaria, rossula; each sex of which differs in colour. This unlikeness is still more apparent in some insects, in which the male has wings and the female none; as in the coccus, lampyrus, phalæna antiqua, brumata, lichenella. And as most insects remain a long while in copulation, as we may see in the tipula and silk-worm, the winged males fly with the wingless females, and carry them about from one place to another; as in the phalæna antiqua. It is, however, no certain rule, that when one insect of the same species is found to have wings, and the other to be without, the former must necessarily be

the male, and the latter the female. The aphides, for instance, are an exception; and besides these, individuals of both sexes, and of the same species, are found without wings, as the carabi majores, tenebriones, melos, cimices. The gryllus pedestris is likewise destitute of wings; and might have passed for a gryllus in its pupa state, had it not been seen in copulation; for it is well known that no insect can propagate its species till it arrives at its last or perfect state.

“Pleraque insectorum genitalia sua intra anum habent abscondita, et penes solitarios, sed nonnulla penem habent bifidum: Canceri autem et Aranei geminos, quem admodum nonnulla amphibia, et quod mirandum in loco alieno, ut Cancer, sub basi caudæ. Araneus mas palpos habet clavatos, qui penes sunt, juxta os utrinque unicum, quæ clavæ sexum nec speciem distinguunt; et fœmina vulvas suas habet in abdomine juxta pectus. Heic vero si unquam vere dixeris, “Res plena timoris amor:” si enim procul in auspicato acceperit, fœmina ipsum devorat; quod etiam fit, si non statim se retraxerit. Libellula fœmina genitale suum sub apice gerit caudæ, et mas sub pectore; adeo ut cum mas collum fœminæ forcipe caudæ arripit, illa caudam suam pectori ejus adplicet, sicque peculiari ratione connexæ volitent.”

Besides those of the male and female, a third sex exists in some insects which we call neuter: As these have not the distinguishing parts of either sex, they may be considered as eunuchs or infertile.

We know of no instance of this kind in any other class of animals, nor in vegetables, except in the class Syngenesiæ, and in the Opulus. This kind of sex is only found among those insects which form themselves into societies, as bees, wasps, and ants: and here these kind of eunuchs are real slaves, as on them lies the whole business of the economy; while those of the other sex are idle, only employing themselves in the increase of the family. Each family of Bees has one female only (called the queen), many males, and an almost innumerable quantity of neuters. Of those, the neuters (whose antennæ have 11 joints) do the working part; they extract and collect honey and wax, build up the cells, keep watch, and do a variety of other things. The males, whose antennæ consist of 15 joints, do no work; they serve the female once, and that at the expence of their lives; they may be considered in the light of a set of parasites, or cecisbei; but as soon as their business of impregnation is over, they are expelled by their servants the neuters, who now shake off the yoke, but yet pay all due respect to their common mother the queen. The same economy nearly takes place in Wasps, where the young females, which are impregnated in the autumn, live through the winter, and in the spring propagate their species; but the queen, together with all the males, perish in the winter. Among Ants, the neuters form a hill in the shape of a cone, that the water may run off it, and place those which are in the pupa state on that side of it which is least exposed to the heat of the sun. At a considerable distance from these are found the habitations of the males and females, to whom the most ready obedience is yielded by the neuters, till a new offspring succeeds, and then they oblige them to quit their habitations. But those ants which live entirely under ground,

ground, provide better for themselves in this respect: for a little before their nuptials, they quit their habitation of their own accord, and after swarming in the manner of bees, they copulate in the air; and each retiring to some new habitation, founds a new family.

No hermaphrodites have as yet been discovered among insects. There is something very singular, however, in the propagation of the aphides. A female aphid once impregnated, can produce young, which will continue to produce others without any fresh impregnation, even to the fifth progeny; afterwards a new impregnation must take place. See Aphis, (Encycl.)

The male insects, like male hawks, are always smaller than the females.

In the propagation of their species they are remarkably careful; so that it is with the greatest difficulty that flies are kept from depositing their eggs on fresh meat, the cabbage butterfly from laying them on cabbage, and other insects from depositing them in the several places peculiar to each. The scarabæus pilularius and carnifex, are deserving of our attention, as they afford a mutual assistance to each other: for when the female has laid her eggs in a little ball of dung, the males, with their feet, which are axiform, assist the female to roll it to some suitable place; as Aristotle and Pliny formerly, and Lœffling has lately observed.

It is very wonderful to observe, that in the coccus and oniscus, the female has no sooner brought forth her young, than she is devoured by it; and that the sphex should be able so readily to kill the caterpillar of a moth, then bury it in the earth, and there deposited her eggs in it. Nor can we without admiration behold the same species of aphid, which was viviparous in the summer, become oviparous in the autumn.

Almost innumerable examples might be brought of the singularities in the eggs of insects; we shall, however, only mention those of the hemerobius, which are deposited on a footstalk; those of the phalæna neutria, which are placed regularly in a ring round the branch of some tree; and the compound eggs of the blatta.

SECT. III. Metamorphoses of Insects.

THERE are no insects, except those of the aptera class, but what are continually undergoing some transformation. Insects change first from the (ovum) egg, into the (larva) caterpillar or maggot; then into the (pupa) chrysalis; and lastly into the (imago) fly or perfect state. During each of those changes, their appearance differs as much as night and day.

The insect, as soon as it came out of the egg, was by former entomologists called eruca; but as this is synonymous with the botanic name filumbrum, it was changed by Linnæus for the term larva, a name expressive of the insect's being, in this state, as it were masked, having its true appearance concealed. Under this mask or skin the entire insect, such as it afterwards appears when perfect, lies concealed, enveloped only in its tender wings, and putting on a soft and pulpy appearance; insomuch that Swammerdam was able to demonstrate the butterfly with its wings to exist in a caterpillar, though it bore but a faint resemblance to its future perfection. The insect, therefore, in this state, undergoes no other alteration but the change of its skin.

The larvæ are, for the most part, larger than the insect when perfect, and are very voracious. The caterpillar of the cabbage-butterfly eats double what it would seem to require from its size; but its growth is not adequate to its voracity.

Pupa. The insect in this state was formerly called chrysalis, or aurelia: but as the appearance of gilding is confined to a few butterflies only, the term of pupa has been adopted in its stead; because the lepidoptera, especially, resemble an infant in swaddling clothes; and in this state all, except those of the hemiptera class, take no nourishment.

Imago, is the third state. This name is given by Linnæus to this third change, in which the insect appears in its proper shape and colours; and as it undergoes no more transformations, it is called perfect. In this state it flies, is capable of propagating its species, and receives true antennæ; which before, in most insects, were scarce apparent.

As the shape of the Pupa is different, in different classes of insects, it assumes different names; thus it is called

Coarctata, when it is round, and as it were turned, without the least resemblance of the structure of the insect; as in the diptera.

Obtecta, when it consists as it were of two parts, one of which surrounds the head and thorax, and the other the abdomen.

Incompleta, when they have wings and feet, but are not capable of moving them; as in most of the hymenoptera.

Semicompleta, in which they walk or run, but have only the rudiments of wings.

Completa, in which they immediately obtain the perfect form of the insect, without undergoing any more change; as in those of the aptera class, except only the flea. The bed bug also belongs to this class.

The spider undergoes frequent transformations, though only in the colour of its skin. The crustaceous insects, as crabs, lobsters, &c. yearly cast their shells, as their growth would otherwise be impeded.

The scelopendri, when young, have fewer feet than when they are full grown.

All insects, as soon as they undergo the third change, are arrived at their full growth; nor do we find any difference in the size of the same species of insect in the same countries, unless, during its caterpillar state, it has not had a sufficiency of proper food.

SECT. IV. Classification of Insects.

As insects are endowed with the various powers of creeping, flying, and swimming, there is scarce any place, however remote and obscure, in which they are not to be found. The great confusion which appeared to the ancients to arise from their number, made them never dream of reducing them to any system. Swammerdam, that indefatigable inquirer into nature, observed that their metamorphoses were divided by nature into several states or orders. Their external appearance also carried with it some mark of distinction: so that entomologists called all those of the coleoptera class, Scarabæi (beetles); those of the lepidoptera, Papiliones; and those of the gymnoptera class that had two wings only, Muscæ (flies); those of the same class that had four wings, were called Apes (bees). No far-

farther progress was made in the systematic part of this science till the time of Linnæus. He was the first that undertook to determine the genera, and assign them their proper characters, in the Systema Naturæ; and thus reduced this science to a systematic form. This system, in subsequent editions, was considerably enriched and amended by him, inasmuch that the science of insects now shines forth in its full lustre. He it was who first instituted natural orders, and reduced them into genera by expressive names; determined an infinite number of species in the Fauna Suecica, and Museum Regium; collected with incredible pains the synonymous names of the various authors who had written on them; and lastly, added their descriptions, and the places in which they were to be found. So that the system of this illustrious author will lead any person, without the assistance of a master, for the most part, easily to ascertain the name of any insect he may meet with. Before his time scarce any more than 200 insects were known; whereas, in the last edition of his system, he has determined the names of nearly 3000 distinct species.

CLASSES. The Linnæan classes of insects are seven; as enumerated in Zoology, and under the article INSECTS, (Encycl.) which see.

ORDERS. These classes are again subdivided into different orders: for which see the articles ZOOLOGY and INSECT, (Encycl.) and Plate CLIV.

GENERA. To insert here the characters of all the different genera which may be found in Linnæus's Syst. Nat. would be unnecessary. It will be sufficient to enumerate some new genera mentioned by the most modern systematic writers, that, by being acquainted with the subtle distinctions on which they are built, the student may avoid running into confusion. It is among the moderns only that genera of this kind are to be met with, and new names given them. To remove this difficulty, we shall first enumerate the names of those authors which are synonymous with those of Linnæus.

New Genera of authors synonymous with those of Linnæus.

New genera of authors.

Copris. Scarabæus absque scutello
Bostrius. Dermestes capecinus
Cistela. Byrrhus Pilula
Rhinomancer. Attelabus rostro producto fere Curculionis
Anthribus. Silpha

Bruchus. Ptinus Fur ob spinas thoracis
Melolontha. Chrysomela cylindrica
Altica. ——— saltatoria
Diaperis. ——— fungorum
Pyrochora. Cantharis
Telephorus. Cantharis
Cantharis. Meloë Alata
Cerocoma. Meloë Shafferi
Notaxis. Meloë Monoceros
Prionus. Cerambyx thoracis margine denticulato
Stenocoris. Leptura thorace spinosa
Hydrophilus. Dytiscus antennis clavatis
Mylabris. Necydalis minor
Acridium. Gryllus Muticus
Locusta. ——— Tettigonia
Tettigonia. Cicada
Corixa. Notonecta.
Naucocerus. Nepa
Perla. Hemerobius cauda bifeta
Libelluloides. Myrmeleon antennis capitatis
Crabro. Tenthredo antennis clavatis
Pterophorus. Phalæna Alucita
Bibio. Tipula thorace spinoso
Stomoxoides. Asilus bucca inflata
Stratonymus. Musca
Nemotelus. Musca
Volucella. Musca.

These genera appear to be in a great measure like those which were introduced into botany by the followers of Rivinus. Paying too little regard to nature, they disunited natural genera, on account of the most trifling distinctions. This made their continuance in the science of very short duration; our business here is not to suppose, but to examine, what nature will allow of, and what she will not. Knowledge of this kind, built on opinion only, will not stand. We are therefore to look into the science with great accuracy; and the larva of the insect, its manner of changing, and other things of moment, are to be known, before we presume to form a new genus.

Coining of new names, and changing of one old one for another, has been the source of the greatest confusion. Thus, in order to reduce the cicindela and carabus to the same genus, buprestis has been adopted for the generic name; but as that genus had long ago received a very different application, it was changed for that of cucujus.

Again, that the officinal cantharides might be ranged among the cerambyces, the cantharides have been removed from the genus of meloë (to which they naturally belong), and referred to the genus of cicindela, obtaining thus a new name. And so of many others.

Thus also, to mention no more, how needlessly and rash was it to separate the acridium and locusta from the genus of gryllus, the crabro from the tenthredines, and the mylabris from the necydalis!

TRIVIAL NAMES. The trivial names placed under their respective genera will occasion little or no controversy; they are current like money, and of the same utility as the proper names of men, Peter or Paul, &c. Insects living on vegetables should receive their names from the particular plants on which they mostly feed, as they are preferable to all others. Thus the names of the phalæna mori, &c. are excellent; and when we are able to give such to insects, the old ones are to be dis-

discarded. But we are to be cautious of not being too hasty in our judgment in this respect; as insects, when they cannot get their favourite food, will often eat other plants. Thus the silk-worm, for want of mulberry leaves, will eat those of lettuce, though it will not thrive so well on them.

Many other instances of the invention of trivial names will be met with in the Systema Naturæ, particularly among the butterflies and moths. To prevent confusion from the great number of species which constitute the genus of phalæna, they are distributed into sections, and distinguished by the terms of bombyces, noctuae, geometrae, tortrices, pyralides, tineæ, and alucitæ. The bombyces and noctuae, which are so much alike, that the females of the bombyces are with great difficulty distinguished from the noctuae, are named promiscuously.

All those of the geometrae have their names terminating in aria and ata, according as their antennæ are setaceous or pectinated. The tortrices, in aria; the pyralides, in alis; the tineæ, in ella; and the alucitæ, in daestyla: so that it is evident from the termination itself to what section the insect is to be referred.

It were to be wished that similar institutions could be formed throughout the whole science, as here the name itself serves to distinguish the insect.

Butterflies are divided into sections, by the names of Equites, Heliconii, Danaï, Nymphales, and Plebeii.

In such a multitude of butterflies, the greatest part of which are foreign and extra-european, and to whose food and manner of life we are utter strangers, it was impossible to give significant trivial names. Linnæus, therefore, by way of simile, has taken the names of the Equites from the Trojan history. These consist, as it were, of two troops or bodies; of which one contains the sable, and as it were mourning nobles, having red or bloody spots at the basis of their wings. These receive names from the Trojan nobles; and as

Priam was king of Troy, the most splendid among these bear his name. The other body, ornamented with a variety of gay colours, are distinguished by the names of the Grecian heroes; and as in both armies there were kings as well as officers of an inferior rank, those elegant butterflies, whose hinder-wings resembled tails, were distinguished by some royal name. Thus when Paris is mentioned, (knowing from history that he was a Trojan, and of royal blood), I find him among those of the first section; that is, those of a sable colour, spotted in the breast with red, and having their hinder-wings resembling tails. When Agamemnon is named, I remember him to be a noble Greek, and find him among those nobles which have variegated and swallow-tailed wings. But when Ne-reus is spoken of, I readily know him to belong to the last section, with wings having no tails.

The second class, which contains the Heliconii, derive their names from the muses, as Urania. The names of the sons and daughters of Danaus are bestowed on the third section. And as these species are subdivided into two other sections, viz. the white and parti-coloured, the metaphor is so conducted, that the white ones preserve the names of the daughters of Danaus, and the parti-coloured ones those of the sons of Egyptus; so that it is evident from the name itself to what section the butterfly is to be referred.

The names of the fourth section, Nymphales, are taken from various nymphs of antiquity; and those of the fifth section, Plebeii, are selected from different men among the ancients whose names are worthy of remembrance: so that by this means a knowledge of the ancients may be interspersed, and this agreeable science be made doubly pleasing.

Those, therefore, who shall find new lepidoptera, and give them new names, will do well to follow this method, unless it be apparent what food the insect chiefly subsists on.

E P A

EPACTS, in chronology, the excesses of the solar month above the lunar synodical month, and of the solar year above the lunar year of twelve synodical months; or of several solar months above as many synodical months, and several solar years above as many dozen of synodical months.

The epacts, then, are either annual or menstrual. Menstrual epacts are the excesses of the civil or calendar month above the lunar month. Suppose, e. gr. it were new-moon on the 1st day of January; since the lunar month is 29 days 12^h 44^m 3^s, and the month of January contains 31 days, the menstrual epact is 1 day 11^h 15^m 57^s.

Annual epacts are the excesses of the solar year above the lunar. Hence, as the Julian solar year is 365 days 6^h, and the Julian lunar year 354 days 8^h 48^m 38^s, the annual epact will be 10 days 21^h 11^m 22^s; that is, nearly 11 days. Consequently the epact of 2 years is 22 days; of 3 years, 33 days; or rather 3, since 30 days make an embellissimic or intercalary month.

Thus the epact of 4 years is 14 days, and so of the rest; and thus, every 19th year, the epact becomes 30 or 0; consequently the 20th year the epact is 11 again; and so the cycle of epacts expires with the golden number, or lunar cycle of 19 years, and begins with the

E P A

same, as in the following table:

Again, as the new moons are the same, that is, as they fall on the same day every 19 years, so the difference between the lunar and solar years is the same every 19 years. And because the said difference is always to be added to the lunar year, in order to adjust or make it equal to the solar year; hence the said difference respectively belonging to each year of the moon's cycle is called the epact of the said year, that is, the number to be added to the said year, to make it equal to the solar year; the word being formed from the Greek εἶναι, induco, intercalo.

Upon this mutual respect between the cycle of the moon and the cycle of the epacts, is founded this rule