DUNG OF CATERPILLARS. 233 



larva of the Sphinx atropos, (which I selected on 

 account of its size,) when placed in cold water, 

 almost immediately resolved itself into three smaller 

 masses in no way connected with each other. Each 

 of these masses subsequently fell to pieces, and was 

 found to consist of small fragments of leaves, not 

 larger than would be taken in at a mouthful, and of 

 irregular as well as variable shape, though mostly 

 approaching the form of a spherical triangle: the 

 whole of these fragments, however, in the case of 

 each of the three smaller masses, were enveloped in 

 an extremely delicate membrane, somewhat resem- 

 bling a cobweb, which was much tangled and folded, 

 and very easily ruptured, letting the small undigested 

 portions of leaf escape. These fragments of leaves 

 were very little altered, and appeared as if they had 

 merely been subjected to compression in order to 

 extract the nutritious particles : under the microscope 

 portions of the ribs were still distinctly visible, as 

 well as the superficial hairs. It would seem, there- 

 fore, that there is no solvent power in the stomach 

 or intestines of the caterpillar, over its food, further 

 than as respects the parenchyma of the leaves they 

 devour, which is alone the source of nourishment. 

 Those caterpillars, therefore, which, as most do, 

 devour the whole substance of the leaf, and the larvae 

 of the subcutaneous Tinece, which never touch the 

 cuticle, are in reality supported in the same way ; the 

 only difference being that the former do not separate 

 the digestible from the more indigestible parts in the 

 act of feeding, swallowing the whole indiscriminately, 

 and afterwards voiding that which has no nourish- 



