HOME-GROWN SILKWORM-GUT 209 



pillar may live long enough to perform its functions 

 of spinning but then dries up and dies. Or the 

 parasite may construct a peculiar kind of cocoon 

 within the larger one spun by the host; such speci- 

 mens are interesting to the scientist but valueless to 

 the one who wishes to rear caterpillars from the 

 egg. As a rule, specimens which have not pupated 

 are easily distinguishable from good ones. The silk 

 of such cocoons is thinner, and when the cocoon is 

 shaken close to the ear a peculiar dry rattle is heard; 

 a good specimen when similarly treated gives a 

 characteristic, unmistakably solid thud. Those spec- 

 imens in which parasites have pupated are not thus 

 distinguishable; only by opening the cocoon and 

 examining the contents can the counterfeit be de- 

 tected. It is not well to disturb the pupa in this 

 way; it is better to watch carefully for the emer- 

 gence of the wasp-like ichneumonides, which should 

 be destroyed when they are perceived. 



While the idea of collecting the cocoons and of 

 getting a supply of eggs from the moths is unmis- 

 takably the best plan, do not be in despair if your 

 cocoon-hunt is unsuccessful. You may be able to 

 capture one or more fertile females in the Spring, 

 which will supply you eggs from which enough cater- 

 pillars will hatch to keep you sufficiently busy. For 

 this variety of " bug-hunting " you will need a net 

 of some light mosquito-mesh, with tin or paper boxes 

 in which to stow away your captures. 



