INSECTS. 



n infu'iKtetl from all its adhefions, ccmflitutes a very from the lower edge of tlie leg, and is infertcd into the 

 ;^* twift, the threads of whiclv, inllead of afting in the lower eminence. 



.,'itiidinal direftion, move obliquely in the canal which The extenfor and flexor of the pincer occupy and divide 

 tlkv occupy between the neighbouring fibres. the interior of the fourth piece : thrir funftions are del'.-r- 



The legs of the cruilacea vary in number and fizc. Tlieir mined by their fituation. The e:;tei'.for of the moveable 

 figures are very different in the monoculi ; fometimes they piece or pollex is a very fmall mufcle, occupying the upper 

 hi'd the place of palpi, jaws, fins, branchia-, &;c. They part of the pinccr : its flexor occupies all the refc of tiiis 

 ditfer confiderably in form in the crabs, particularly the iirll part, is a very bulky mulcle, and lias a flattened oblong 

 ]>xr. We fliall defcribe the legs of the crab and lobller bony tendon in its middle. From this mufcle arifes the 

 as an example of thefe organs. They are ufually five in great power of the animal in feizing and holding objects, 

 number on each fide, and each has fix articulations. The Organs of Molkn in the Larva: of InftBs. — As inftcts 

 iirll pair is confiderably the largeft, and forms what we call undergo confiderable changes of form at certain epochs of 

 thj claws. their life, they^exhibit remarkab'e difT'rend s in their organs 



The hip, or hnunch, is attached to the cheft, and moves of motion. Hence it becomes necefiary to defcribe tFieni in 

 only from before backwards. It fupports one divifion of their various ftatcs. All the win ^cd infcfls, svhich undergo 

 the branchix, a;; well as the fecond piece of the member, a complete metamorpliofis, differ very confiderably in their 

 which correfponds to the thigh. The latter is flattened, firft Hate frijtn that which they have in the fequel ; and the 

 fliort, nearly fquare, ^nooth, and a little curved. The plane moft ilriking of th-fe differences regard the moving powers. 

 <.f iii articulation is parallel to the length of the piece ; and At this time they are called larvje or caterpillars ; and they 

 •he two mufcles which move it are inferted into the two preferve this form for a longer or fliorter time after quitting 

 t remote points, the thigh is fituated horizontally. It the egg. They are covered with a flaccid and foft Ikin, 

 a hi-ige-like motior on the hip, combined of the two divided into fegments or rings fufceptible of motion on 

 diicciions from before backwards and from within outwards, each other, by means of fmall mufcular bancs fituated in 

 its motion on the leg, which is very limited, takes place the interior of the body. Frequently their motions are 

 only from below upwards, and produces the approximation performed fimply by crawling on thefe rin.;s, after the 

 of the limb to the chell. The third portion correfponding manner of reptiles ; or, by retting fuccelTively each of the 

 to the leg is alfo ra'her flattened, particularly at its femoral fegments of the bcdy on the plane which fupports it. 

 extremity. It is fiightly curved in the dircclion of the Such is the cafe with the larvae of the diptera, and of moil 

 thigh, fo as to correfpond to the convexity of the thorax, of the hymenoptera. Sometimes the furface of thefe rings 

 Towards the tarfal end it becomes larger and rougher : its is fiirnifhed «Hth fpines, Iliff briftles or hooks, in order to 

 motion on the thigh is very limited. The fourth articula- give them a firmer hold on bodies : this may be obferved in 

 tion is intermediate between tl:e pincer and the leg, on forae flies, oellri, tipulae, &c. 



which it moves in a very diiiindt angle. The pincer com- On the under furface of the body in fome orders, there 

 pofcs the fifth, and by far the larf^^it piece. It is terminated are fix feet near the head, each of which is formed of three 

 on the outfide by a pointed and ferrated projeftion ; and articulations : the laft is horny and terminated in a hook, 

 it receives on the oppofite fide a moveable pointed piece By oppofing tliefe to each other the infett can hold any 

 or pol'ex, capable of being cppofed to it, which, with the objeft, hook itfelf to it, and then draw the reft of the body 

 other, conftitutes the pincer. The motion of this on the towards this fixed point. This formation is feen in the 

 fourth piece is from without inwards. The two following coleoptera, and many of the neuroptera. The fix feet are 

 pairs of legs refemble the former on a fmaller fcale, with very (liort, and hardly fufceptible of any ufeful application 

 this difference, that the two pieces, compofing the pincer, in fome other coleoptera, •vix. fi.ch as live in tlie ulterior 

 are of equal fize. The two lafl: pairs of legs differ from of wood, as the cerambices, rhagia (Fab.), &c. The latter 

 the three others in not being terminated by a pincer, but move in the hollows which they excavate by means of 

 by a fingle nail. In every other refpecl they refemble the their jaws, by which they attach themfelves, and with the 

 two precedmg pairs. affuhince of plates or tubercles, with which their flcin is 



. Alufda of the Legs. — Each artic,ulation has an extenfor furuifiied on the back and belly ; their mode of proceeding 

 and a flexor mufcle. The extenfor of the hip is fituated may be compared to that of fweepers in chinmies. 

 in theinterior of the thorax, on the horny piece which fup- Laftly, the lepidoptera, and fome hymenoptera have, be- 

 ports the branchii, rather in front of the hip, which it fides the fix horny articulated feet, a variable number of 

 draws forwards. The flexor arifes from the fame part falfe feet, not articulated, terminated by hooks difpofed in 

 farther back, and produces the contrary motion to the circles and half circles, and attached to the (kin on retra'lile 

 preceding. appendices or tubercles ; they move by fixing themfelves to 



The extenfor of the thigh is ftronger than the flexor ; it bodies by means of thefe organs, 

 is attached to the inner and front part of the hip, and to The lana- of fuch infers as undergo an incomplete mc- 

 the fuperior eminence of the thigh. It dcpreffes rather than tamorphofis, as the hcmiptcra, and of fuch as pafs through 

 bends. The flexor, or rather the elevator of the thigh, is none at all, as the aptera, except the flea, do not differ from 

 fljorter than the former ; it occupies the pof'erior internal the perfect infect in the feet. 



Turface of the thigh, and is inferted into the inferior emi- After this general ftatement of the external organs of 

 aence. motions in the larva;, we fliall particularly defcribe the 



The extenfor of the leg is placed in the hollow of the mufcles of fome. We fliall firft mention thofe of the pro- 

 thigh, of which it occupies the whole breadth ; it is inferted per caterpillars ; then thofe of a fcaraba^us, which lives under 

 'into the external border of the leg. The flexor is lefs ground ; of a hydrophilus, which inhabits the water ; and of 

 powerful, lies under the extenfor, and is fixed to the inner a cerambyx, which is found in the hollows of wood, 

 edge. I. Mufilej ofCcittrJiil/arJ.—'l'lK docpeft ftratum of muftiea ' 



The extenfor of the firft piece of the tarfus is attached in the caUrpillar is formed of four principal rows ; two cor- 



t/3 the whole upper edge of the leg, and is inferted into refponding to the back, and twoto theb^-lly : their dircdion 



the highell eminence of the fourth piece. Its flexor arifes is longiUidinul. Thofe of the back arc feparated from cacK 



Vol. XIX. X o'Avx 



