INSECTA. 



971 



the common cavity of the oesophagus, although 

 not separated from it by a valve, neither is the 

 oesophagus separated by a valvular structure 

 from the gizzard. The chylific stomach is ex- 

 ceedingly long and cylindrical, but is without 

 gastric coeca, like the larva of Carabidte, since 

 like that, the Panorpa appears to subsist rather 

 by sucking the juices than by swallowing the 

 hard parts of the body of its victims. Thus, 

 then, although in the Cicindelidie (Jig. 37, vol. 1), 

 the canal is scarcely longer than the body, as 

 formerly shewn by Dufour, and since fre- 

 quently instanced as proving that the length or 

 shortness of the canal is characteristic of a car- 

 nivorous or phytophagous feeder, we cannot 

 admit that the length of the digestive organs, 

 and the existence of a gizzard and gastric ves- 

 sels, are indicatory of predacity of habits in the 

 insect, because a similar conformation of parts 

 exists often in strictly vegetable feeders. The 

 existence and length of these parts seem rather 

 to refer to the comparative digestibility of the 

 food than to its animal or vegetable nature. 



Among the more omnivorous feeders, as in 

 the Forficulida, the gizzard is still present. 

 In Forjicula auricularia the oesophagus is 

 long and dilated, and a short, broad, and very 

 muscular gizzard is present. Internally it is 

 thrown into six longitudinal folds, which pro- 

 ject for some distance at their extremity into 

 the cavity of the digestive stomach, to the en- 

 trance of which, when closed, they serve as a 

 valve. The canal of this insect, which, although 

 in part carnivorous in its habits, certainly is 

 not of the most rapacious nature, but lives 

 equally upon the juices of fruits and flowers, is 

 scarcely longer than that of the most predaceous 

 Cicindela or Dyticus, since it passes almost in 

 a direct line through the body, making but one 

 slight convolution, a further proof that the 

 length of the canal must not be taken as a cri- 

 terion whereby to judge of the habits of a 

 species. This will apply equally to the om- 

 nivorous Gryllidte, in which there exists a short 

 alimentary canal, but a gizzard of more com- 

 plicated structure than that of Dyticida. In 

 these insects the two layers of the mucous 

 coat are visible even in the oesophagus. The 

 second layer is distinctly glandular and secre- 

 tory, and in it there are many thousands of 

 very minute granulary glandular bodies, which 

 probably secrete the fluid that is often ejected 

 from the mouth of the insect when captured. 

 The inner layer, or proper mucous lining, is 

 often folded longitudinally, and in Acrida 

 viridissima these folds, which are six in number, 

 assist to form a valve between the oesophagus 

 and gizzard. They are each armed with five 

 very minute hooked teeth, and continued into 

 the gizzard develope many more in their course 

 through that organ. These first teeth are ar- 

 ranged around the entrance to the gizzard, and 

 seem designed to retain the insufficiently com- 

 minuted food and pass it on to that organ. 

 Next to these in succession on each of the lon- 

 gitudinal ridges are four flat, broad, and some- 

 what quadrate teeth, each of which is very 

 finely denticulated along its free margin. These 

 extend about half-way through the gizzard. 

 They appear to be alternately elevated and de- 



pressed during the action of the gizzard, and to 

 serve to carry on the food to the twelve cutting 

 teeth with which each ridge is also armed, and 

 which occupy the posterior part of the organ. 

 These teeth are triangular, sharp-pointed, and 

 directed posteriorly, and gradually decrease in 

 size in succession from before backwards. Each 

 tooth is very strong, sharp-pointed, and of the 

 colour and consistence of tortoise-shell, and is 

 armed on each side by a smaller pointed tooth. 

 These form the six longitudinal ridges of the 

 gizzard, between each two of which there are 

 two other rows of very minute teeth of a tri- 

 angular form, somewhat resembling the larger 

 ones in structure occupying the channels be- 

 tween the ridges. The muscular portion of the 

 gizzard is equally interesting. It is not merely 

 formed of transverse and longitudinal fibres, 

 but sends from its inner surface into the cavity 

 of each of the large teeth other minute but 

 powerful muscles, a pair of which are inserted 

 into each tooth. The number of teeth in the 

 gizzard amounts to two hundred and seventy, 

 which is the same number in these Grylfaue 

 as found formerly by Dr. Kidd* in the mole- 

 cricket. Of the different kinds of teeth there 

 are as follows : seventy-two large treble teeth, 

 twenty-four flat quadrate teeth; thirty small 

 single-hooked teeth, and twelve rows of small 

 triangular teeth, each row being formed of 

 twelve teeth. This is the complicated gizzard 

 of the higher Orthoptera. In the same insect 

 immediately posterior to the gizzard the chylific 

 stomach is expanded on each side into two 

 large rounded cceca, into the upper part of which 

 some minute vessels are traced which in appear- 

 ance resemble the hepatic vessels. Posteriorly 

 to these coeca the stomach becomes narrowed 

 and makes one convolution, and receives around 

 its termination the hepatic vessels, which are 

 small but very numerous. It then is continued 

 backwards as a long ilium, and terminates in a 

 muscular banded colon without a distinct 

 rectum. The whole length of this alimentary 

 canal does not exceed more than about one 

 length and a half of that of the body. A simi- 

 lar structure exists in the Blattida. In these 

 insects eight large vessels are inserted around 

 the commencement of the stomach behind the 

 gizzard. Four of these are long and four short, 

 and as observed by Burmeister, these have been 

 thought to be analogous to pancreatic or 

 gastral salivary organs. In the proper Locust ida 

 there is only a rudimentary gizzard, as Bur- 

 meister has shown in Locusta migratoria, in 

 which the interior lining of the whole oeso- 

 phagus and crop is covered by an immense 

 number of very minute horny teeth, for the 

 purpose of comminuting the hard ligneous 

 matter which we have sometimes found in 

 foreign specimens. The rudiments of the 

 gizzard exist in six flat pieces, studded with 

 minute teeth like the lining of the oesophagus. 

 The commencement of the stomach is sur- 

 rounded by two sets of coecal appendages, six 

 in each set, and similar in form to those of the 

 second set in the larva of Melolontha, like 

 which those on the under surface are the 



* Phik Trans. 1826. 



