ICHNEUMON FLY. 215 



The caterpillars of many of the Papilios are 

 provided with a retractile fleshy fork on the 

 back of the neck just behind the head, and these 

 must be specially useful for driving away their 

 worst enemy, the ichneumon fly, whose horrid 

 habit is to pierce the bodies of caterpillars and 

 lay an egg in the wounds so made. When the 

 young are hatched they feed on the body of the 

 poor caterpillar, which, strange to say, does not 

 die at once, only gradually gets thinner and 

 thinner. 



This is one of the disappointments attending 

 the rearing of larvae, for the wounds pierced are 

 not easily noticed, and sometimes the first 

 intimation one has is seeing the caterpillar 

 completely covered with tiny white cocoons. 

 None of the caterpillars I have had so attacked 

 have ever recovered entirely, though they have 

 lived on for some days after the cocoons were 

 removed. Sometimes the egg is inserted just 

 before their change to pupa, and then, instead 

 of butterflies or moths, these horrid flies emerge, 

 causing much regret. 



