150 ANATOMY. 



but it is still the stomach only which shortens, until it decreases to 

 scarcely one half of its former extent. 



In the Lepidoptera, on the contrary (PI. XVIII. f. 4. caterpillar ; 

 5. imago), the intestinal canal lengthens, but so that here also the 

 stomach becomes shorter but the ilium longer. In the caterpillar the 

 broad, cylindrical, folded, and transversely ringed stomach occupies 

 more than two-thirds of the entire intestinal canal, and this is succeeded 

 by a shorter, scarcely narrower ilium ; the preceding pharynx is short, 

 and so short that it is observed only in the head. Contiguous to the 

 stomach lie the long twisted spinnerets, and attached to it are the six 

 united biliary vessels. In the imago the pharynx is long, and beneath 

 it lies the sucking stomach, of which we observe no trace in the cater- 

 pillar ; the stomach, on the contrary, is small, short, ovate, folded, and 

 narrow ; the ilium, again, long, filiform, twisted ; the colon broader, 

 elongated above into a short caecum, which is likewise deficient in the 

 caterpillar. The spinnerets disappear, but the salivary vessels, which 

 are very small in the caterpillar, become more distinct, larger, and 

 longer. 



We have already noticed the very interesting metamorphosis of the 

 intestinal canal in the wasp and the bee. In the order of the Hymeno- 

 ptera also the law prevails of the stomach becoming smaller and nar- 

 rower whilst the pharynx and ilium become longer. This will also 

 apply to Myrmecoleon, in whose larva the colon becomes the spinneret. 

 But of all the orders the Coleoptera display the greatest changes of 

 the intestinal canal. The larvae of the carnivora wholly want the folded 

 horny orifice of the stomach (PI. XIX. f. 1 and 3). Their stomach is 

 broad, but smooth, and not beset with filamentary processes ; the ilium 

 is also broad, but short, and much shorter than after the metamorphosis. 

 This consists in the crop distending, the proventriculus forming itself, 

 and the stomach sending forth filamentary processes. In the Cara- 

 bodea the ilium becomes much longer ; but in the water beetles, where 

 it is already very long, it appears to become somewhat shorter, at least 

 in Dyticus marginalia, according to Dutrochet, whose investigations 

 I have repeated, and can now confirm (see PL XIX. f. 3. the larva ; 

 f. 4. the beetle). In the vegetable feeders, namely, in the Lamelli- 

 cornia, the intestinal canal in the larvae is triflingly longer than the 

 body, whereas in the perfect insect it is three or four times as long. 

 The larvae have a long, broad, cylindrical stomach beset with filaments 



