THE ORGANS OF NUTRITION. 137 



that it may consistently be considered as deficient. This deficiency in 

 them may be accounted for by the number of their stomachs, for that 

 transmutation of the food which is properly the function of the ilium 

 takes place in their third stomach, and which consequently renders the 

 ilium unnecessary. 



With respect to its structure, we have already indicated some of its 

 >eculiarities in treating upon the membranes of the stomach. Those of 

 the ilium are generally tenser than the latter ; it is invariably equally 

 distended, and, as it were, inflated, whereas the stomach is not un- 

 usually folded up. We have already mentioned that the ilium, as well 

 as the stomach, is frequently transversely ridged, and by this means is 

 distinguished from the duodenum. 



The length and situation of the ilium varies considerably ; it is rarely 

 so long or longer than the body (Necrophorus), in general shorter, and 

 even shorter than the stomach. The latter proportions are found espe- 

 cially in the Chrysomelina, and in many others which feed upon 

 vegetable matter it is the general rule. In many of the carnivora, for 

 example, the water-beetles (Hydrocantharides^, the ilium on the con- 

 trary, is longer than the stomach, particularly in their larvae, in which 

 it is twice as long ; but this is not the case in the ground-beetles 

 (Cicindelacea and Carabodea}, the ilium in them being not so long as 

 the stomach. The butterflies have the longest ilium, in proportion to the 

 stomach of all insects, for in them it is not merely twice as long, but 

 even three or four times the length of the stomach, which is the more 

 extraordinary as in the caterpillar it is excessively short, scarcely 

 extending to one-eighth of the length of that organ. In the Diplera 

 also it is shorter than the stomach ; in the bugs alone is it sometimes 

 wholly deficient. It is regularly wanting in the Libcllulcc and 

 Ephemera. There are no fixed laws which regulate the length of the 

 ilium, but Ramdohr has endeavoured to show its most prevalent pro- 

 portions to the stomach and the other parts ; they are as follows : the 

 most usual relation to the stomach is as 1:1, or 1:3; to the whole 

 intestine 1 : 5, or likewise 1 : 3. Some of the proportions are extra- 

 ordinary, as in Necrophorus, viz., the ilium to the intestinal canal as 

 2 : 3, to the stomach as 9 : 4 ; indeed, this beetle has the longest ilium 

 of any yet investigated. In Tenthredo nigra it is very short, viz., in 

 proportion to the entire nutrimental canal it is as 1:17- In the cater- 

 pillars of the butterflies it is always very short, and in general it is 



