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alike, and the ftigmata are placed in the fame manner. The eyes however of the two kinds fufficiently diftinguifh them ; the fauffe cbeville having only two, and thofe very large and prominent, and placed on each fide of the head ; whereas the caterpillar has five eyes on each fide of its head, and thofe placed in a circular direction, and too fmall to be feen with- out the afliftance of glaffes.
The Fauffe Chenilles are a clafs of animals almofr as numerous as the caterpillars. They are eafily diftinguifhed into feveral genera, according to the different number of legs, as thofe with eigh- teen legs, thofe with twenty, twenty-two, and twenty-four. The fauffe chenille of the alharia is of this laft kind. They are of feveral colours in the different kinds ; fome are white, fome brown, others black, but the greateft number of all are green. There are many of a Hate colour, or bluifh black variegated with ftreaks and fpots of brown, and other colours. And befide thefe, there are others variegated on feveral other grounds ; in general, however, they are much inferior in beau- ty to the caterpillars. The colours of thefe infects are how- ever very indiftinct marks to difcern them by, fince they are not permanent, but the creature varies them at different times of its life. Thefe infects, like the true caterpillars, change their skin feveral times in their lives, and with it they change their colours alfo. The young ones of thefe animals are al- ways much more hahdfome than thofe more grown ; for at every change of the skin there is a lofs of fome of the va- riegations j and ufually at the laft change they are all gone, and the creature puts on a colour different from any that it bad before. This is an obfervation of the accurate Vallifnicri, who gives an inftance of it in a worm caterpillar of the elder. This creature, while young, is of a fine green, with a long ftreak of brown running all the way down the back ; but af- ter the laft change of its skin, it appears without the ftreak, and all over of a pale yeilowifh hue.
Thefe creatures differ from the common caterpillars in their manner of remaining on the leaves of a plant. The caterpil- lar is always extended at its full length, whether it is eating or not ; but the fauffe chenille, though it extends its body to the full length while eating, always rolls it up into a fpiral when at reft, making feveral circular turns with it, of which the head is at the end of the outermoft, and the tail in the very center of the inner one. They give themfelves various odd contortions when they are feizing on their food ; and it is a very whimfical fight to obferve twenty or thirty of them, in thofe kinds which live in fociety, attacking the different por- tions of the fame leaf all at once, and each giving its body fome odd turn at the fame time. This is a common fight on the leaves of the ofier; a whitifh green kind, being very fre- quent in large companies on that tree, and often ken thus feeding tn coveys. It is remarkable, that as the caterpillar feeds indifferently on every part of the leaf, this animal ufu- ally attacks only the edges.
Some fpecies of thefe animals feed only early in the morning, and as the leaves are then wetted with the dew, they cannot avoid taking in a large quantity of water with their food ; in confequence of which, when they are examined afterwards, their bodies are frequently found cover'd with drops of a thick and vifcous water of an ill fmell. It feems probable, that the abundant aqueous matter in this cafe finds its way out at thofe jiumberlefs apertures in the skin, at which the creature takes in the air: thefe infects, as well as the caterpillars, having very numerous tracheae.
The generality of the animals of this clafs feed on the leaves of plants and trees, but there are fome which affect other parts of them. There are a fmall fpecies very frequently found living within the young branches of the rofe tree, which often deftroy that part of the fhrub. Others are found Iodg'd in young pears, apples, and other fruit. They feem to have been placed there when very young, and always deftroy the fruit, occafioning its falling off from the ftalk before half grown. Some fpecies of them are alfo found on the leaves of trees, which are render'd tumid, and make what are called leaf galls, thefe being often inhabited by animals of this clafs, in particular the leaf galls of the willow. The creature, when it finds the time of its change into the nymph ftate ap- proaching, gives itfelf the trouble of forming a cafe in which it may pais into that ftate, and remain in it during the deftin'd time without being fubject to external injuries. It fpins a web of filk for this purpofe of the (hape of a little egg. This on the outfide ftiews nothing remarkable ; but when cut open, it is found to be compofed of two different fubftances, at leaft of two fubftances of very different workmanfhip, though the materials are the fame in both. The outer cafe is reticulated, and formed of very ftrong threads wove into a loofe open net- work; but the inner one is formed of extremely fine threads, and thofe wove into a clofer fluff than all that the loom can come up to. The outer ftrong and coarfe web was plainly intended for no other purpofe but for the better defending and preferving them from injuries. And thefe two diftinct cafes do not any where adhere to one another, but barely touch ; fo that on pulling afunder the outer one between the fingers, the inner one comes out whole. The ftrength of this exterior fliell is extremely necefTary, as alfo the clofe texture of the Suppj.. Vol. I.
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inner one, for the deeding the inclofed animal in the nymph ftate from feveral devouring infers. The ants in particular are very fond of thefe nymphs, and will hunt out the cales where-ever they are to be found ; and if they can eat their way through them, are fure to make a meal of the inclofed creature.
The rofe worm or fauffe chenille is very Angular in the man- ner of its performing this great work. This is a fmall green- ifh fpecies often found on the leaves of the rofe, and famous for the various odd attitudes into which it twifts its body occasi- onally It ufually carries its tail erect, and often in the fhape of the letter S. 1 hi, fpecies, tho' green on the fides and belly, is yeilowifh on the back, variegated with feveral fpecks of black or deep brown, from each of which, there grows a long hair. This creature when the time of feeding is over goes into the ground in order to fpin its double web. The external one is of a reddifh brown, and the internal one whitifh. Thefe when taken out of the earth are ufually foul'd with fmall particles of dirt, fo that to have them in perfeaion, it is beft to keep the animal in a box, where it will fpin them perfectly clear. There are fome fpecies of this animal, that hide themfelves in the holes of trees, and in the cav'ties between the bark and the wood, and thefe never fpin any Outer web, but are found inclofed in the fine thin internal cne alone. They all, after having paffed a proper rime in this ftate, fome only a few weeks, others a whole winter, become four winged flies. The flies produced of thefe infects are of that kind which have no trunks, but have a ftrong tooth on each fide of the head, which meeting one with the other in the middle of the mouth, are able to cut any thing to pieces that the creature has occafion to make its way through. The firft ufe of thefe is the eating a hole through the double web, in which the creature finds itfelf enclufed at its birth. All the flies of this kind, have a general refemblance one to another, and may be known to belong to the fame family, tho' they are very different in colour, and other obvious characters. They are never very handfome, and are all as it were ftupid, having very little motion,and flanding readily at any time to be caught between the fingers. Their wings always are croffed over the body and form a fort of raifed covering over it ; they are not fmooth and even, as thofe of moft other flies, but have pro- minencies and cavities, and feem as if they had been but ill expanded at the time of the creatures hatching from the nymph ftate. Reaumur' '$ Hift. Inf. v. 9. p. 133. The feveral fpecies of thefe flies, which are very numerous, differ much left from one another, than the creatures do in their reptile ftate. They are of different colours indeed in their bodies and wings, and have fome of their effential parts of different ftrutture, but they are often very like cne another in the fly, when they have been extremely different in the worm ftate, fo that their difference in colour, &c. are not al- ways to be expected in the feveral fpecies, which are ever [6 diftinct. The bodies of fome are black, thofe of others arc greenilh, and thofe of others yellowifh, and the wings in ge- neral are colourlefs and tranfparent, tho' in fome, they are tinged with grey, and in others with yellow, the antenna? are alfo very different in the feveral kinds, in fome they are granu- lated and in others they are of the elevated kind, the antennae of the male and female of the fame fpecies often differ alfo very confiderably.
All the females of thefe flies are oviparous, no one fpecies pro- ducing living worms; and as thefe eggs muft netefiarlly be lodged in cavities or niches, made in the ftalks or leaves of living plants, nature has provided this creature with two in- ftruments, which are deftined for this fole purpofe, and which are real faws made in the niceft manner, with extremely fmall teeth. The creature has the power of ufing both thefe at once, and confequently can make an aperture with great eafe, that fhall be fufficient to lodge its eggs in. Notwithftand- ing that there are many different fpecies of flies which have this fort of inftrument, and feveral of them are extremely frequent on one of the moft common of all our garden fhrubs, the rofe-tree; yet no author had obferved this elegant and wonderful inftrument, till the time of Vallifnieri, who has defcribed and figured at large the weapons of a rofe- tree -fly, produced from a falfe caterpillar of that fhrub, with two rows of teeth, one on each fide in the man- ner of the faw of the ferra pifcis, or faw-fifh. It muft be obferved, that there are different fpecies of this infect, fince Mr. Reaumer's figures and defcriptions from the inftru- ments we faw on the fly of the fame tree, exprefs only one row of teeth in the hw, and make it like our common hand- faws with a plain back. It is neceffary to have recourfe to the microfcope in order to fee diftinctly this Angular inftrument, yet the naked eye alone, fhews fo much of it, as to eafily en- gage us in a defire of knowing it better. If the body of the fly be fqueezed gently, there will be feen an opening between two plates of a hollowed figure, which are lituated near the anus, and this opening gives a fight of a fine brown point of a flender body to be feen within j on farther preffing the body of the fly, the whole inftrument, of which this is the point, is forced to {hew itfelf, and the whole faw is placed before the eyes. The two hollow pieces which opened in order to fhew 11 C it,
