INSECTS. 



Aift bridles or teeth, is tlie maxilla properly fo called ; 

 the other is the feeler. The lower lip has two very finall 

 palpi, and a hollow point in the middle : this is the fpin- 

 ning hole, through which the filk comes out, employed by 

 the caterpillar for forming its coccoon. 



The Mufcks. — When the upper lip is moveable, it is 

 drawn backwards by two bundles of flefliy fibres fituated 

 j within the cranium, and which are themt'elves divided into 

 ! two planes. The motions of the mandibles are analogous to 

 j thofe of the hips in infefts. At the bafis, on the fide cor- 

 J refponding to their convexity, there is a kind of condyle, 

 ' or convex rounded eminence, received into a fmall cotyloid 

 ; cavity, excavated in the temporal fcale m front of, or below 

 ' the eye. On the fide correfponding to the cutting edge 

 of the mandible, there is commonly obferved, at leaft in 

 large infects, fuch as the fcaraba^us monoceros, the prionus, 

 * the capricorne (cerambyx), the lucanus cerviis, the locufta, 

 a kind of iolid tendinous plate, which is apparently pro- 

 longed into the interior of the folid parietes, and aflords 

 attachment to mufcular fibres implanted in it laterally, as 

 the barbs of a feather are on the common fhaft. Thefe 

 mufcles approximate the jaws to each other, or fhut the 

 nu. :th. i'hofe which feparate the mandibles and open the 

 '1 are much fhorter, and not one-tenth of the fize of 

 ■ceding. They are inferted in a fmall apophyfis, cor- 

 :,Jing to the convex external line of the mandible, on 

 the oiitfide of the condyle. Lyonet has defcribed and figured 

 tliefe mufcles in the larva of the phalasna cofTus. He calls 

 them adduftors and abduftors ; but he has regarded as fo 

 many diftinft organs, the fafciculi of fibres inferted into the 

 common tendon ; fo that he has diftinguillied nearly eleven 

 mufcles or bundles deftined to clofe the mouth, and three 

 principal planes for the purpofe of opening it. Thefe 

 fibrous planes are found in all other infefts ; but very great 

 varieties are obferved in their number and relative difpofition. 

 Thefe differences depend evidently in the firft place on the 

 very different infertions of the tendinous plates, which are 

 to be confidered as prolongations of the mufcles : they 

 feem alfo to be modified by the length and fize of thefe 

 plates. The latter always have a relation to the form and 

 extent which the internal parietes of the mandible and of the 

 cranium afford for their infertion. 



Salivary Organs. — No exprefs organ, for the purpofe of 

 fupplying a falivary fecretion, has been hitherto difcovered 

 in the crullacea ; but the place of falivary fluids is fupplied 

 in the following manner. The branchiae, placed at the fides 

 of the body, under the edges of the corfelet, are comprelTed 

 and agitated by the cartilaginous plates connefted to the 

 jawj and feet ; at this time, the water in contatl with the 

 branchiz flows along thefe plates, and comes out at the two 

 fides of the mouth ; hence, when a crab or lobfter is taken 

 out of the water, much froth is obferved to ilfue from that 

 part. This water, although foreign to the body, may ferve 

 to moiften the food, when the animal eats out of water. 

 At other times no faliva can be needed, as in the cetacea and 

 filhes. 



Many infefts furnilh, during maftication, more or lefs fluid, 

 which is often acrid, and of a penetrating odour, and fup- 

 plies the place of faliva. In the carabi it is black and 

 foetid, very corrofive in fome grylli ; and capable, in the 

 larva of the coffus, of foftening and dilfolving the wood of 

 the willow, on which the animal feeds. 



The fources of thefe fluids arc not yet known in all fpecies; 

 probably, however, they are produced by organs analogous 

 to each other, and thofe of one fpecies may ferve as an 

 example of the reft. The larva of the coffus has two long 

 fpongy veflels, like all the fecretory organs of infefts, very 

 Vox.. XIX. 



much convoluted, and opening into a large refervoir, wIiicFi 

 communicates with the mouth by a fmall canal. This or- 

 gan feems to produce a liquor, nccefliary to the animal for 

 the purpofe of afting on the wood by which it is nourilhed. 

 It is deficient, or very fmall in moft oth^r caterpillars. 



Organs of Deglutition. — I ft. In infefts with jtws. The 

 membranous extremity of the lower lip, in the coleoptera, 

 and the orthoptcra, which has been called a tongue, fcarc-ely 

 deferves that name. But in the fecond of thefe faTiiilies 

 there is a real flefliy tongue, loofc only at its point, and 

 analogous in ficmre to that of quadrupeds. The odonata, 

 among the neuroptera, have a ilrufture fomewhat fimilar ; 

 but the tongue of the hymenoptera is only a membranous 

 tube, often open be'ow, and forming the extremity of the 

 lower lip. In the wafps, and in all the h)Tnenoptera, which 

 have no trunk, it has an arched form, being open and con- 

 cave below, and more or lefs divided into pieces. The 

 bees, and all the hymenoptera which have a long trunk, 

 poflefs a complete tube with annular fibres : fuftion is per- 

 formed by the fucceffive contraction of thefe fibres. 



2diy. In infefts without jaws. Since deglutition is the 

 firfl aft of nutrition in thefe infefts, the form of the organ 

 employed in fuftion determines the fpecies of juice which the 

 animal can imbibe, and confequently influences very confi- 

 derably its way of life. The relations of the natural families 

 of thefe animals to their organs of fuftion, are much more 

 conftant than they are to the inft^ruments of iTiafl;ication in 

 the other half of the clafs. There are four orders of infefts 

 without jaws, -viz. hemiptera, lepidoptera, diptera, ap- 

 tera ; and there are three kinds of fuclion particularly be- 

 longing to the three firfl; of thefe. The hemiptera have a 

 ilitf probofcis enveloped in a flieath ; the lepidoptera a mem- 

 branous trunk fpirally convoluted ; the diptera a trunk 

 terminated by two flelhy lips. Hence the names of rhyn- 

 gota, gloflata, and antliata applied by Fabricius to thefe 

 three orders ; which he has preferred the fame as in the 

 Linnsan arrangement, and which many others had adopted 

 before. 



The greatefl; varieties are obferved in the diptera. In 

 this order the organ confifts eflentially of a flefliy trunk, 

 divided below into two lips more or lefs proloni;cd, and 

 capable of being applied to the object which is to be fucked : 

 two tentacula are detached to the root of this trunk. Be- 

 tween the latter is a pointed fcale, fometimes employed to 

 cut the veflt^ls from which the fluid is to be fucked, but 

 often ferving only to cover other pieces, which are much 

 fliarper and more appropriate to this funftion. In the 

 ftratyomys, and the common flies, there is merely a fingle 

 fliort point under the fcale. The fyrphi and rhingias have 

 in addition a ftiff' brilUe under each palpus. In the rhagio 

 there are three briflles under the fcale, and the middle of 

 them is the llrongeft. The tabani have four, all pointed 

 and fliarp like the blades of lancets ; hence thefe infefts 

 have the power of inflifting the ieverell wounds on the 

 flcin. All the parts are much elongated in the genera empis 

 and bombylius ; the trunk is more particularly extended 

 than the brillles in the latter, which indeed have only one 

 bridle under the fcale. In the empis all the parts are equally 

 prolonged, and there are four brillles. 



In the myopa (conops, Linn.) the trunk is elongated into 

 a flender tube with an angle at its middle ; there is a fliort 

 fcale without any bridle. In the afilus and domoxvs (co- 

 nops, Linn.) the trunk is hardened, and afl'umes a horny 

 texture, fo that it is capable of cutting. There is a fingle 

 bridle within it in the ftomoxys, and three in the afilus. The 

 trunk is reduced almod to nothing in the hippobofca ; and 

 the fingle bridle is long and flexible. 



Z All 



