INSECTS. 



The earwig is faid to be very different from the other 

 orthoptera in having only a fimple elongated ilomach, a very 

 ihort inteiliiie, and a dilatation with longitudinal folds near 

 the anus. 



III. In the Hymenoptera. — The bees have a firft ftomach, 

 ■which is membranous and tranfparent, pointed in front, large 

 and divided into two portions behind. In this organ the 

 neftar of the flowers is converted into honey : it is the refer- 

 voir of this matter, which they depofit in their hives by the 

 aft of vomiting. The fecond iioniach proceeds from the 

 interval of the two divifions ; it is elongated and fwoUen 

 laterally towards the middle. The hepatic veflels are inferted 

 immediately after the pylorus. The firft inteiline is fmall, 

 and fcarcely equal in length to the fecond ftomach : the 

 rectum is large but ftiU Ihorter. 



The firft ftomach of the wafp is fmailer ; the fecond 

 longer, and particularly much more mufcular. The larvae 

 of both genera have an immenfe cylindrical mufcular ftomach, 

 filling nearly the whole abdomen, and followed by a very 

 iliort inteftine. 



In the fphex the ftrufture refembles that of the bee ; the 

 parts are only larger in proportion to their length. 



IV. In the Neuroptera. — The family of the odonatse, 

 which is truly carnivorous, has very fhort inteftines in its 

 three ftates : they do not exceed the length of the body. 

 In the hbellula grandis, Linn, a lliort cefophagus is fucceeded 

 by a fmall ova' mufcular ftomach, ftriated longitudinally ; 

 then comes a ftraight large inteftine or fecond ftomach, with 

 a conftriftion placed far back at the entrance of the hepatic 

 veflels. The interval between this part and the anus is 

 very ftiort, and folded longitudinally. In its larva, the 

 eefophagus has a circular dilatation : the conftriftion of 

 the cordia produces a kind of valve. From this point the 

 canal has a bright yellow colour, as far as the infertion of the 

 hepatic veflels ; its lall portion is white and much thicker ; 

 and contains the fingular refpiratory apparatus, which we 

 fliall defcribe afterwards. 



In the family of the agnatha, the ephemera, during its 

 larva ftate, has merely a ftraight uniform canal, without any 

 convolution, which becomes extremely thin in the perfeft 

 infeft. 



V. In the Hemiptera. — Thefe poflefs in general a fimple, 

 oval, and mufcular ftomach, of coiifiderable fize, followed 

 by a fmall inteftine of moderate length, near the end of 

 wliich is a fuia'l cscum. Such at leaft is the cafe in the 

 nepa, notoiicfta, &c. 



VI. In the Lepidoptera. — The caterpillars have a large, 

 fhort, ftraight, inteftinal canal, without any confiderable 

 inequalities. The cefophagus is the flendereft portion, the 

 ftomach is elongated and contrafted at the pylorus. After 

 the pylorus the inteftine is larger than in the reft of its 

 length ; it is contrafted towards the anus. At the latter 

 part it has the ftrongeft circular fibres ; on its parietes other 

 fibres are found, varioully decuffated and ending in two 

 white lines, winch extend over its whole length, one above, 

 and the other below. The diameter varies in different fitua- 

 tions, according as the contents are accumulated. Sumc- 

 times the dii'inftion between the ftomach and inteftine can 

 fcarcely be obferved. 



This canai is obvioufly calculated for folid and abundant 

 food. The butterfly, whicli fubfifts entirely on the juices of 

 vegetables, has a very different digeftive apparatus. Among 

 the diurnal infefts of this order, the atalanta has a flender 

 oefoph igus, with a membranous dilatation on its fide, hke a 

 crop, more or lefs rounded in its figure, and often full of 

 air. Then comes a fecond elliptical membranous ftomach, 

 the fides of which prefent many hemifpherical cellular pro- 



minences ; and afterwards a third, cylindrical, and ratiit. 

 mufcular, followed by a fmall inteftine of moderate length, \ 

 terminated by a rather larger reftum. I 



VII. In the Diptera In general their inteftinal canal is 



tolerably long in both ftates. It is five times the length of 

 the body in the larva of the ftratyomys, and confifts of a 

 fhort cefophagus as flender as a thread, a very fmall oval 

 ftomach, and an inteftine, of which the firft half is wrinkled 

 tranfverfely, which becomes afterwards larger and fmoother 

 to the infertion of the hepatic canals, below which it is fud- 

 denly conftrifted and remains nan-ow. The differences 

 between this and the larva of the fyrphus are very flight ; 

 and the diftinftions between both and their perfeft infefts are 

 not more obvious. However, Swammerdam reprefents four 

 fmall caeca, after the ftomach, in the larva of a fly which 

 inhabits cheefe ; Cuvier has not found them in the diptera 

 diffefted by himfelf. 



VIII. In the Gnalhaptem. — The fcolopendrx have a long 

 canal contrafted behind ; the iuli have an equally, long and 

 cylindrical one. We have already mentioned that of the 

 onifcus. 



IX. /n the /Iptera luilhotit Jaics. — The loufe has two fmall 

 fwellings at the origin of the ftomach, which is elongated ; 

 the inteftine is not longer than the ftomach ; it is fmall, and 

 terminated in front of the anus by a mufcular enlargement. 



Hepatic Vejfeh. — Although the cruftacea have a heart and 

 blood-veffels, moft of them have not a liver, properly fo 

 called. The organ which produces bile in them confifts of a 

 confiderable number of fmall tubes ending in cul-de-facs. 

 The ftrufture is analogous to that of the pancreas of fifhes, 

 which confifts, as we fuppofe, of the multitude of caeca 

 opening at the origin of the inteftine. 



The appearance of the hepatic caeca in the cruftacea dif- 

 clofes their nature and office ; they are yellow, have fpongy 

 fides ; produce a brown and bitter liquor, which gives its 

 peculiar tafte to the foft fubftance in the body of the lobfter ; 

 for the hepatic csca, with the ftomach, fdl nearly the whole 

 thorax of thefe animals ; and, in the hermit crab, they fill 

 alfo a great part of the tail. 



The fquilla. Fab. is an exception to this rule ; thefe ani- 

 mals have a liver of a firm texture, very much refembhng a 

 conglomerate gland, confifting of lobes arranged on each fide 

 of the alimentary canal in its whole length. 



In the infefts, properly fo called, there is ftill lefs appear- 

 ance of liver than in the common cruftacea. Since they can 

 have no glands on account of the abfence of blood-veffels, the 

 bile, hke all the other fecretions, is produced in them by 

 fine veffels with fpongy fides, floating in the fluid, which 

 bathes all the parts, and deriving from it, by the organiza- 

 tion of their tiffue, the elements proper for the formation of 

 this liquor. 



Thefe veffels exill equally in the larva and in the perfeft 

 infeft: the fluid, which they form and contain, tinges them 

 with its own colour. They are ufually ye;lo\v, fometinies, 

 as in the fcrabxi and cerambyces, of an opaque wliite ; and 

 in other inftances, as in the dytilci, of a deep brown. Their 

 bitter tafte arifes from this fluid, which would probably be 

 found to poffefsmanyof thequaUties of bile, if it could be 

 procured in fufficient quantity for analyfis. 



The number of theie veffels is variable ; when it is large, 

 they arc fhort, fo that the extent of furface is nearly the 

 fame. Sometimes they all end in a common excretory tube, 

 which terminates in the inte.line. This is the cafe with the 

 gryllo-talpa. They are common'y inferted after the ftomr.ch, 

 bat fometimes not till near the middle of the inteftinal > ', 

 as in the grylli ; or even towards its end, as in the lib. 

 The onifci alone have them inferted near the ccfophagi 



