NSECTS. 



line, others more laterally. They form, in general, two faf- 

 ciciili. The moft internal is tlie lead bulky. The lateral 

 fi;xors are very oblique. They arife from the inferior or 

 .ibdominal part of the body, and extend to the Literal parts 

 of the occiput. The inferior flexors, which bend it down- 

 ward, appear to be the continuation of the llraiglit mufcles 

 of the belly. They confilt of eight or nine fafciculi. 



2. Mufcks ofthi Larva of a Scarabceus. — Thi larva: of the 

 rc.irabxus have the body arched, and convex fuperiorly, and 



:cave on the fide next the feet. The back and the belly 

 loparated by a membranous border, which has folds, and 



iiluated under the ftigmata. Thefe larvas have only fix 

 niticiilated feet, none of which are membranous. On open- 

 ing thefe larvae longitudinally, eitlier on the back or the 

 belly, we obferve three layers of decp-feated mufcles — the 

 lateral, the dorfal, and the ventral. 



The dorfal layer is formed of two tolerably diftinft feries 



of fibres. One feries is external, and occupies the intervals 



J of the ten firft rings ; that is to fay, thofe which are furnifhed 



I with the ftigmata. The mufcles which compofe this feries 

 are narrow, and preferve a longitudinal dire£lion. The 

 \ fecond feries is produced by fibres, which are fomewhat 

 oblique, and extended in the fame fpace, but more towards 

 the middle line. Thefe mufcles are broader and ftronger 

 towards the head, and more narrow and lefs fibrous towards 

 the tail. They terminate between the tenth and eleventh ring 

 by a very narrow flefhy band. Thefe mufcles feem intended 

 to (horten the dorfal portion of each of the rings : this aftion 

 diminifhes the convexity of that part, and thereby ferves to 

 aflift progreffion. 



Near the middle line, between the ninth and tenth ring, 

 there are two fmall mufcles a little oblique ; but between 

 the twelfth and the laft ring we obferve only one feries of 

 fmall fhort mufcles, which occupy all the convexity defcribed 

 by the curvature. The action of thefe mufcles is obvioufly 

 the fame as that of the preceding, to which they are accef- 

 fories. 



When the firft layer of dorfal mufcles is removed, we find 

 fibres precifely fimilar underneath, but running in the oppo- 

 fjte direction. Finally we obferve, in the dorfal layer, lines 

 of very (hort mufcular fibres above the infenor plane of the 

 ninth and tenth ring. The ufe of thefe Uttle mufcles is pro- 

 bably the fame as that of all the preceding, though their 

 aftion is lefs apparent. 



The ventral layer very much refembles that of the back. 

 Thefe mufcles, like the dorfal, form planes of oppofite 

 direftions ; the moft deep-feated proceeding from tlie inter- 

 nal fide, while thofe which are neareft the ikin afcend from 

 the external fide. This produces a fmall but very regular 

 rhomboidal figure ui the middle of each ring on the line 

 bifefting the belly. The aftion of thefe mufcles is the op- 

 pofite of that of die dorfal layer. 



On the laft fegment, and towards the part that anfwers to 

 the anus, we obierve a bundle of tranfverfe fibres, which, 

 by their contraft:ion, doubtlefs ferve the purpofe of a 

 fphinfter. 



The lateral layer of mufcles is compofed of three kinds of 

 fibres, which are verj' diftinft with rcfpeft to their courfe. 

 They reprefent a lace pafted through the mefties of a net. 

 All thefe mufcles are fituated behind the ftigmata, and in- 

 ferted into the folds which feparate the belly from the back 

 on both fides. 



Thofe of the firft order are completely tranfverfe. They 

 extend over the union of each ring with the fuccceding in the 

 fpace included between the ventral and dorfal mufcles. It 

 is obvious that they miiftdiminifli, by their conti-aftions, the 



diameter of the body, and coiifequently extend it longitudi- 

 nally. Thefe mufcles are in general very narrow. 



The fecond fet is formed by oblique fibres which afcend 

 from without inwardly towards the middle ventral line, from 

 the union of one inferior ring to the union of the preceding. 

 Thefe mufcles are broad and very ftrong, they ferve to form 

 the folds of feparation between the back and the belly. 



The mufcles of the third order are lefs oblique than the 

 preceding, to which they appear to be acccftbries. Each 

 of the mufcles which com])ofe this divifion arifes from the 

 middle of a ring, and is inlerted under the head, where the 

 preceding mufcles are infertcd, that is to fay, on the ventral 

 fide. 



It (liould be remarked, that the two laft rings have na 

 lateral mufcles. 



The mufcles of the head are very llrong, the flexors are 

 attached to the ventral mufcks above the union of the fe- 

 cond ring with the third. They are formed of three prin- 

 cipal fafcicuh, which approach each other, and are inferted 

 into the pofterior and inferior part of the head, at the bafe 

 of that fcaly piece called, by Latreille,^a«(wZr. The exten- 

 fors or levators of the head confift alio of three fafciculi, 

 but they are longer and iiroiigcr tlian the former. They 

 have their origin in the fide, and penetrate under the tranf- 

 verfe and obhque mufcles ; one is attached to the fixth 

 ring ; another to the fifth, and another to the fourth. 

 They are inferted into the pofterior lateral parts of the 

 head. 



3. Mufcles of the Larva of a HydrophUus. — The larvae'of 

 the hydrophili are elongated. Their body is fomewhat flat, 

 and all its rings .nre diftinft. They not only walk very 

 quick, but they even fwim with great velocity, in coiife- 

 quence of different inchnations fuddeiily and fucceflively 

 given to the body. 



Thefe larvs, when opened longitudinally, likewife 

 exhibit four different kinds or divifions of mufcles: 

 thofe of the belly, thofe of the back, and thofe of both 

 fides. 



The ventral mufcles very much refemble thofe of cater- 

 pillars : they are formed of two dillinft layers. The dcepeft, or 

 that which firft appears on the belly^when examined through 

 an opening on the back, is compofed of longitudinal fibres 

 with interfeftions which correfpond to each ring ; the fecond 

 layer, or that which is next the fl^in, is entirely covered by 

 the preceding ; it is compofed of oblique fibres, which crofs 

 each other in the form of an X, and which are extended 

 longitudinally in each ring. 



The dorfal mufcles are long, extending from the head 

 to the tail, and forming on each fide two rows of fibres, 

 which appear twilled over each other like ropes. They are 

 broadeft' towards the head. T'hcir fibres are inferted partly 

 into the inferior border of an anterior ring, and partly, into 

 the fuperior border of the next ring. 



Thefe long mufcles cover fome which are obhque, and 

 crofs each other in the form of an X. They extend from 

 the middle part of one ring to the anterior edge of that 

 which fucceeds it. 



The deep-leated lateral mufcles, which are numerous, 

 have a tranfv.-rfe direftion. Each ring has three or four, 

 and their courfe is fuch, that they refemble the letters N or 

 M lying on one fide, thus g 2; . 



Beneath tiie tranverfe lateral there are fome longitudinal 

 mufcles that have a fmall degree of obliquity : they form a 

 pretty large furface, which is uninterrupted throughout its 

 whole length, and confounded with the oblique mufcles of 

 the bflh . Their fibres determine the chief motions of the 

 . X 2 body. 



