INSECTS. 



The {IvuAurc of tlic mandibk- is the moll fingular in the The other murde is inferted in a particular eminence no .>• 

 fciiiilla. It is dindcd into two parts; an anterior one con- the middle of the oppofite or fixed edge. Its fibres : 

 cealed under the lip, directed accordinff to the axis of the (liort and mnneroiis. They pafs downwards and backwai'J , 

 body, pointed, and having two rows of fmall denticulations ; and are fixed towards the middle hne of the bony cafe <f 

 ;i poilerior trant'vcrfe one, with the cutting edge direfted the cheil. Their contraction will produce a contrary cfi'crt 

 froni.below upwards, and pofTefling a row of llronger denti- to that of the preceding mufcle ; that is to fay, it will draw 

 cnlatiors. AH thefe mandibles have feelfrs : they are com- the edge of the mandible away from that of the oppofite 

 pofed of three articulations, and dilated at the end in the fide. 



lobiters, crabs, &c. ; of throe articulations, and pointed in There appear to be two Other mufcles in the crab, having 

 the fquilla ; of a fingle piece in the fcyllarus, See. the fame funftions ; but they are fituatcd at the articulated 



The'entomolh-acea vary ftill more than the ordinary cruf- extremity of the mandible. Each articulation of the feeler 

 tacea. The moliicca crab (monocuhis polyphemus, Linn), contains two mufcles, a llexor and an extenfor ; of which 

 has five pairs of maxillie. Ihort, comprelTcd, 'and covered with the former is the largeft. The flexor is placed in the 

 fmall fpincs ; each pofTcirng a very large palpus like a foot, broadell part of the concavity of the mandible ; it is in- 

 with four articulations, terminated by a pineer like that of ferted in a fmall bony tendon fituated at the anterior edge of 

 the fore-feet of the crab and lobiler. The pincers of the the articulation. The extenfor is more (lender, and attached 

 foft pair are very large in the male. Thofe of the lall are to the fixed edge of the mandible ; it is attached by a long, 

 fmall, and accompanied by fome fcaly laminx. In front of and (lender tendon to the pofterior edge of the articulation 

 thefe maxillx is the upper lip, of a prifmatic figure, having of the firfb piece. The mufcles of the two other pieces of 

 two palpi compofed of two pieces, and terminated by pin- tiie feeler are arranged nearly in the fame manner, 

 cers. The lower lip is behind the laft pair of maxillse, and 

 is formed of two denticulated plates. The monoculu? apus 

 has two ftrong and toothed mandibles, then two pairs of 

 fmall maxilix without palpi, and laiHy twenty-fix other 

 pairs of broad plates refembling maxillx by their bafes, and 

 branchise in the rell of their extent, and of which the firft 

 has four palpi refembling articulated briiUes : three of thefe 

 are very long, and have been taken by fome for antennx. 

 Thefe twenty-fix pairs of plates occupy nearly the whole 

 iMider furface of the body. 



The maxillx are moved from within outwards, and reci- 

 procally, by mufcles analogous to thofe whicli we have juft 

 defcribed as belonging to tiie mandibles ; and the pieces 

 which compofe them, when they confift of feveral articula- 

 tions, contain in their interior two mufcles, an extenfor and 

 a flexor, very fimilar to thofe of the legs. 



Moreover, each of the maxillae, and particularly of the 

 lower ones, has, on the piece conefponding to the hip in the 

 legs, one, two, and fometimes three laimnx direfted inte- 

 riorly to the cavity of the branchis ; thefe will be confidered 

 The fmaller entomoflracea have been very little examined in the account of refpiration. 

 in refpeft to the organs of the mouth. The family of the Jaws of Iiifcfls. — ift. In the Gnathaptera (Cuvier.) 

 onifci refembles the cruftacea in the multiplicity of their — This order obferves no common law, like all thofe which 

 jaws, as by their four ant'^iinx ; perliaps it ought even to be are founded on negative charadlers only ; it muft be divided 

 entirely aflbci :ted to tlieni. The firit pair, which has alfo into families, in order to obtain fome general rules. The 

 been called the lower lip, although it is clearly divided into firft, that of the millepedes, affords none ; for the iuli have 

 two halves, is plane, and covers all the others : it has a very only fmall mandibles, under which is a conical piece com- 

 fmall feeler on its external angle. Next to this come two pofed apparently of the lower lip and the maxillx conloh- 

 or three thin oblong pairs, of which the fccond is denticulated dated together, without any feeler. The fcolopendrx have 

 at its end: thefe have no palpi. The mandible is ftrong, denti- fmall mandibles, larger maxillx without pa'pi, a pair of 

 culated, and has a fmall conical feeler. Thefe organs are ex- palpi under them, and a large lower lip, of which the arti- 

 ceedingly diminiflicd in the parafitic fpecies, as in the cymo- culated and pointed palpi form together a ftrong pineer. 

 thox (Fab.), which have only two pairs of maxDlx, hke The fecond family, or the arachnidx, has ftrong mandibles 

 fmall fcales, fmall, conica', obtufe mandibles without teeth, which cannot cut, but are armed at their extremity with a 

 and in the middle of the whole a fmall conical tongue. The moveable hook, often forming a pineer, with a prominence 

 pycnogonum ceti (Fab.) has no vifible Jaws, although we of the body perforated for fucking. The maxillx are 

 can ftiU difcern two articulated palpi. The proper place fcareely vifible, and only ferve to fiipport palpi, which are 

 of thefe, as well as of the other pycnogona, cannot at prcfent always very long, and in the form of feet, and fojnetimes 

 be affigucd. But fi)me parafitic infefts, which have been ar- enormous, as in the fcorpions, where they referable the claws 

 ranged among the entomoftracea, do not belong to that clafs, of crabs. In the phryues, where they furnifli the animal 

 .and liave a fucker, like fleas. Such are the numerous calygi with a formidable weapon, there is neither lower lip nor 

 (Cuvier) found on the gills of filhes, &c. labial palpi. AVe might contcil the propriety of calling 



Mufcles of ihe Jaws. — The mandible is moved on thecheft thefe organs mandibles, finre they ferve for fucking and not 

 by two mufcles. One ftrong and long approximates its loofe for mafticating ; but their pofition, and the analogy of other 

 edge to that of the oppofite fide, and at the fame time elevates infefts, forbid us to refufe them this name. Fabricius has 

 it.^ It is fixed by two diftinft flefhy portions to the membrane founded the charafler of his clafs of unogata on the fmall 

 which covers the thorax interiorly above and on the fides of moveable hook which terminates them. 



the ilomach. One of thefe pieces is anterior and fmaller : The third family, that of the riciiii, w fleas of birds, has 

 it is compofed of fliort radiated fibres, terminating in a only mandibles, betweeil which is a fmall roftrum, and ap- 

 flender bony tendon, articulated to the tendon of the firft pears to have neither maxillx nor lips. Thoie of the Iqjifma 

 portion, of which it appears to be an angular produdion. and podura have not been fufiiciently examinetl. 



The largeft portion is lefs oblique ; it is fituated between the 2dly. la the Neuropterti This order is not much more 



'liver and ftomach : its fibres, more numerous and alfo ra- conftant than the preceding in the forms of the mouths of 

 diated, terminate at the extremity and front edge of the the infedis belonging to it. W'e meet firft with the beau- 

 common bony tendon, which is itfelf fixed to the middle of tiful family of the aguatha, infeiils deftined to live fcareely 

 the loofe edge of the mandible, which it tends to elevate by a few inftants in the perfeft ftate, and po(fcfling merely what 

 .drawing it towards that of the oppofite fide, is necelTary for copulation and laying. Tiify have no occa^ 



lioa 



