Grub Parasite in the Snail. 437 



burrowing in the body of the snail. They evidently, from 

 their appearance, belonged to some species of beetle, and we 

 carefully preserved them in order to watch their economy. 

 It appeared to us that they had attacked the snail in its 

 stronghold while it was laid up torpid for the winter; 

 for more than half of the body was already devoured. They 

 constructed for themselves little cells attached to the inside 

 of the shell, and composed of a sort of fibrous matter, having 

 no distant resemblance to shag tobacco, both in form and 

 smell, and which could be nothing else than the remains of 

 the snail's body. Soon after we took them, appearing to 

 have devoured all that remained of the poor snail, we 

 furnished them with another, which they devoured in the 

 same manner. They formed a cocoon of the same fibrous 

 materials during the autumn, and in the end of October 

 appeared in their perfect form, turning out to be Drilus 

 flavescens, the grub of which was first discovered in France 

 in 1824. The tim<3 of their appearance, it may be remarked, 

 coincides with the period when snails become torpid. (J. K.) 



In the following autumn, we found a shell of the same 

 species with a small pupa-shaped egg deposited on the lid. 

 From this a caterpillar was hatched, which subsequently 

 devoured the snail, spun a cocoon within the shell, and 

 was transformed into a small moth (of which we have not 

 ascertained the species) in the spring of 1830. 



[Before concluding the account of the parasite insects, it 

 will be necessary to mention two of our British Ichneu- 

 monidae, which not only deposit their eggs in the larve of 

 other insects, but make for themselves cells of very beautiful 

 structure. In the accompanying illustration are shown the 

 cells of one of our commonest and most useful ichneumonidss 

 (Microgaster glomeratus), together with the insect itself. At 

 Fig. la (p. 438) is shown the little insect of the natural size, 

 and the same is given at 1 much magnified. 



[This creature lays its eggs in the body of the cabbage 

 caterpillar, forty or fifty eggs being deposited in the same 

 larva. They soon hatch into little transparent grubs, which 

 lie under the skin, and live on the fatty parts of the cater- 



