Page:Cyclopaedia, Chambers - Supplement, Volume 1.djvu/746

 FLY

F L Y,

teeth or other organs, by which the creature gets its food. The firft example of thefc heads is in the fcorpion fiy; and a very beautiful// that is frequently feen skipping and leaping about flowers is the other.

Under thefe general claffes, fubordinate ones are to be formed, from whatever befides is the inuft obvious and eflential diftin- clion among thefe little animals. The form of the body may very well afford us thefe.

Some files have bodies fhort and of an oval figure, refembling an elJipfoide or a truncated ellipfoide figure, more or lefs flat- ted. Of this figure is the body of the common great blue flefh fly, fuch is alfo the form of the body of the bee kind, and of multitudes of other files both of the two and four winged kinds, whofe bodies are as broad as thick. Among the ellipfoide bodied files, fome have a rounder, others a more oblong body, others a thicker, and others again a thin- er or flatter, and others have the hinder part of it bent un- derneath like a hook. Of this kind are the Jlies common about excrements, and a little grey fiy common about the bloilbms of the pear-tree.

Some files there are however, which are longer and rounder than thefe, and deferve to have a peculiar clafs alloted for them. Of this kind are the libellre, commonly called with us dragon- fties and demoifelles by the French. Others have their bodies fhorter but cylindric, as the gnats ; and others have them co- nic, as the common corn/?/, which refemblcs the fcorpion^r?/, and is found in the harvett-time among the corn. Others fi- nally have bodies in the form of a fpindle ; that is, long, and thicker in fome part between the ends, than at the ends. Thefe might be arranged in a peculiar clafs, and called the large bodied files, that is to fay, files whofe bodies are long in proportion to their thicknefs.

The flies whofe bodies are of this fpindle fhape, may very properly be taken from the other clalfes, and made to efta- blift a new one, for this reafon, that as the whole anterior part of the body is in other files joined to the corcelet, in fuch manner, that they feem united in their whole furfaces; thefe on the contrary are not joined body and corcelets together, neither indeed do thefe parts touch, but are united by means of a flendcr filament, as may be obferved in the hornets, and others of the wafp clafs. In fome files this filament is very long, and in others, as remarkablj fhort ; and in fome, after it has been extended to fome length, from the corcelet, very thin and fine, thickens by degrees as it approaches the body of the fiy, as in the greater part of the ichneumon files. There ' is great difference among the different fpecies of the ichneu- mons, fome inftead of the common long body have a fhort and thick one faftened to the corcelet by a very ilender thread ; fuch are the ichneumons of the oak galls. Under the five former claffes we have therefore three other fubordinate ones; the firft of thofe files whofe bodies are fhort and broader than they are thick; the fecond of thofe with long bodies; and the third of bodies faftened to the corcelet only by a fine filament. And under all thefe, the feveral ge- nera are to be eftablifted from other leffer but conftant and invariable differences ; fuch as the differences of the manner of their carrying their wings, the figures of their antenna;, the pofition of their trunks, and other the like differences. Reau- mur's Hift, Inf. torn. 4. p. 124. feq. See Tab. of Infeifs, and the articles Wings, Trunks, &c. Bodies of Flies. The bodies of thefe infers are extremely dif- ferent one from another, and even thofe whofe general form makes them properly ranged in the fame clafs, are not with- out their diftincfions, by which they alone may be made to eftablifh fubordinate genera.

Among the files which have fhort or ellipfoide bodies, fome have the body extremely flat and thin ; fuch are thofe of the files produced from the worms which devour the pucerons ; and others have the hinder part of the body bent downward in form of a hook.

The extremity of the body in thefe animals is ufually fmaller than the adjoining parts. Yet there is a/?y found in the ncfts of fwallows, the extremity of whofe body is larger than any other part of it ; and not only the form of the bodv, but the differences of the filament,by which in many genera,' it is con- necfed to the corcelet, may furnifh great matter for the dif- tincfion of the fubordinate genera.

The hinder part or extremity of the body alone may alfo af- ford great matter of diftinaion. Thofe flies which carry flings in their tails, have in that alone a fufficient diftinflion. Reaumur's Hift. Inf. torn. 4. p. 144.

Others there are which have organs placed there, which tho' we need not fear them, offer fubjefl enough for our admira- tion; 'tis indeed the females alone, who have occafion for thefe, and therefore the females alone are furniflied with them.

Several of thefe mftruments are a kind of auger or borer, car- ried in a cafe or fheath. This fometimes has the form of a long tail to the inlia, and its ufe is to pierce and bore the body, in which the creature is to depofit its eggs. Several of the female ichneumons have this fort of long tail ; and there are other iufefts which have a long and ftrong piercer, which

however does not make a tail to their body, but is partlv loda'd either under their belly, or in their bady ; of this kuid'are The cicadas and others.

Other infefls of- this kind have a lingular inftrument lodr--;d |., this part of their body, which may properly be called a'-Ja*. They never ftew this on examination uulcis their bodies' b- prefled, and then we cannot but greatly admire the ifiitru ment itfclf, and the powers by which the creature moves

Other infefis of this clafs carry behind one or more long-flen- der filaments, which in their form and ftruflure, have fome fort of refemblance to the antennae ; and the ufes of which are as little known to us, as thofe of the antennae. The <*e- nera of flies may very properly be diftinguifted by means'of thefe : among the four winged fiies, the cphemerons, and many other fpecies, have them ; and among the two win^d kind, the finally, which is the male gall-infeft, furniftes lis with an mftance of them. See Tab. of Infefis.

Fl 1 es of water worms. Thefe according to their feveral fpecie* have fome vanties in their manner of egrefs from their fheii at their leaving the nymph ftate, for that of the perfeft fit The long water worms compofed of many rings, and with funnel fafhioned tails made with an aperture for theadmiffion of the air, furrounded with a multitude of hairs, retain, in their fhell ftate, fo much of the fame form they were of while living, that the one is not eafy to be diftinguifhed i'om the other. The nymph in each of thefe fills up only a fmall part of the cavity, and the fly in many of them is producej perfect in five or fix days. At this time tjie parts of the nymph being thorough/ ftrengthened, it begins to fliew the firft hgns of life in its attempt to open its prifon. , To effea this, nature has fo provided for the inc'lofed fly that the head is but ffightly joined to the fecond fing of the body'- but the creature in this ftate, not being lodged in that part of the worm, can make no efforts againfi it; ail its endea vours are bent to force a flit or opening in the fecond rin» like that in the back of the skin of a caterpillar, that is goin* to change its skin, or like that of the butterfly cryfalis'? The means the inclofed fly ufes to this purpofe, are the inflal ting and fwelhng its head, and then thrufting out the bladder from its anterior part, with which thefe files are provided bv nature m this ftage of their lives, and for this only purpofe When this flit or crack is c-ffeaed, the head of the worm is. in fome meafure feparated from the body, and the efforts of the fiy to pufh itfclf forward, finilh that reparation, and leave an aperture of a proper fize, for the egrefs of the fly But the water, en the furface of which this change is efiia ed, is a thing much to be dreaded, and indeed is often of fa ta. confequences to the new born fly, fince the files produced of water worms, are as much afraid of this element and are as eafily drowned as thofe produced from worms who fiend their lives on dry land. *

The flies produced from this long water worm, are however m lefs danger and lefs afraid of the water than many others - they advance flow.'y out of their fliells in an horizontal direc- tion, and as foon as their fore-feet are at libertv, they boldly place them upon the water, as if upon dry land,' and it ferves as well for their fupport; and as their other parts get at liber- ty, they are gradually fet upon the water too, and the crea- ture there refts till his wings are unfolded, and all its parts have their proper form, and then takes its flight into its new element.

The fiy produced from this long worm is of the fliort bodied kind, and much of kin to the common great blue flefh fi; It has a Hefty trunk fumifted with lips, and has no teeth'; but tho this fiy ,s fo far of the fame clafs with that common fpec.es, it has enough to amply diftinguifh it ,n thefe feparate characters The firft ,s, that this has its antennae formed of granulated filaments, whereas the other has them of the bat- tledore kind: the wings of the flefh fiy are not croffed upon the body, whereas, thofe of this water/?/ are; but what more man thefe dift.ngmftes it from this, and indeed from all the other fpecies of fiies is, that it has two oblong and (lender bo- dies formed like pins, and pointed as thofe, which are a little crooked, of a cruftaceous ftruaure, and are inferted in'the upper part of the corcelet of the fiy, and direSed toward its hinder part.. See Tab. of InfeQs, N°40, feq. Thefe prickles are hard, rigid and immoveable.

Si. Mark Fly, in natural hiftory, the name of a fpecies oS- fly which makes its firft appearance every year, about St. Mark I day, and is then feen in vaft numbers ; it is fomewhat fmall- er than the large blue flefh fly, and has no trunk, but a mouth without teeth: notwithftanding this leemingly inno- cent organization, the creature does great mifebief, Snd every gardiner knows the effeas of it at one time or other." Thtfe files are found about fruit trees, and are always feen fitting up- on the buttons of the leaves, and the flower buds; and^licy do great mifchief to many kinds of trees, by fucking the juices of thofe tender parts, and either deftroying them before they open, or at leaft rendering them very weak. Some tell us that thefe flies had originally a fting, but that the mif- chief they did, being very great, St. Mark deprived them of

that