-NOTES ON NORTH AMERICAN MICROGASTERS. 



299 



spin their cocoons more or less closely connected together, some- 

 times to the number of several hundred. In the *' Proceedings of 

 the Entomological Society of London" for 1872, p. xxiii., Prof. 

 Westwood notes an instance in which 1,000 individuals were 

 bred from one larva of a large Ceylonese Bomb3xid. 



T h e victimized 

 caterpillar ceases 

 feeding as the para- 

 sitic grubs attain 

 full growth, and ge- 

 nerally shrinks con- 

 siderably as soon as 

 they have penetra- 

 ted the skin and 

 spun their cocoons. 

 Fig. 3 shows a 

 healthy full grown 

 "•Hog-caterpillar of 

 the Vine" ( Cheer 0- 

 campa panipina- 

 when shrunken and para- 



Fig. 3. Healthy 



trix), and Fi 

 sitized. 



of Chncrocampa pampinatrix 

 (After Riley.) 



4 the same caterpilh 



rocampa pampinatrix, with 

 Microgaster cocoons. (Afier 

 Rilev.) 



" It is one of those remarkable and 

 not easily explained facts, which often 

 confront the student of Nature, that, 

 while one of these Hog-caterpillars in 

 its normal and healthy condition may 

 be starved to death in two or three days, 

 another, that is writhing with its body full of parasites, will live 

 ■without food for as many weeks. Indeed, I have known one to 

 rest for three weeks without food in a semi-paralyzed condition, 

 and, after the parasitic flies had all escaped from their cocoons, 

 it would rouse itself and make a desperate effort to regain strength 

 by nibbling at a leaf which was offered to it." * 



The cocoons are usually egg-shaped and resemble miniature 

 cocoons of the Mulberry Silk-worm. They are either smooth 

 and glossy, or more or less covered with flocculent silk. When 



* Second Report on the Insects of Mo. 1S69, p. 73. 



