CHAP. XXVII INSECTA : HYMENOPTERA 445 



explanation of the varied larvae sometimes found within 

 the same gall. 



Allied to the Gall Wasps are the parasitic 

 "wasM**'' Ichneumon Wasps, most of which lay their eggs 

 in the body of a caterpillar. The soft, legless 

 larvae live within the host, either until the moment for 

 pupation has arrived, or until the perfect insects are about to 

 break free from the pupae, when the parasites may emerge and 

 pupate outside the body of their victim. One such Ichneumon 

 is Paniscus testaceus (Fig. 327), the larvae of which are parasitic 

 in the caterpillars of Hadena pisi, one of the Owlet Moths. 



Apanteles ( = Microgaster) is a form which is very similar, 

 but which differs in the nervures of the wing and in 

 the much less mobile abdomen, hence it is classified in a 

 separate family from the true Ichneumonidae. One species 

 of Apcmteles {A. glomeratus) attacks the caterpillars of the 



„ „„_ „ . , , Fig. 328.— Caterpillar of Pieris 



Fig. 327. -Panwus testaceus. brassicae Infested witli Apan- 



A common Ichneumon Wasp. teles glomeratus (Braconidae). 



Cabbage White Butterfly, laying a great number of eggs in its 

 body. The larvae of the parasite develop within, absorbing the 

 juices of their host without at first apparently incommoding 

 it, for it eats voraciously all the time and appears healthy. 

 Finally, however, the larvae emerge through its skin in order 

 to pupate, and the caterpillar usually now dies, though, even 

 in the enfeebled condition in which it is left, it has been 

 occasionally known to complete its development. Each of 

 the parasitic larvae, when free from the body of their host, 

 spins a little yellow silk cocoon, and these cocoons lie in a 

 mass by the side of the infested caterpillar (see Fig. 328, B). 

 From these pupae emerge the perfect insect (Fig. 328, A). 



