200 



ELEMENTAEY STUDIES IN INSECT LIFE 



generally attacked, the caterpillar frequently pupates; 

 and so, in collecting chrysalids, especially lepidopterous 

 ones, for emergence, one or many of these hymenoptera, 

 instead of the form corresponding to the pupal case, may 

 come forth from the case. 



Fio. 175. Parasitic hymenopteron (Thalessa lunator) drilling with ovipositor 

 Into burrow of the wood-boring larva of the pigeon horn-tail. (After Riley.) 



The accompanying figure (Fig. 175) illustrates a 

 parasitic hymenopteron 1 at work. This is one of the 

 larger insects of the order. It is parasitic upon the 

 wood-boring larva cf the pigeon horn-tail, 2 another hy- 

 menopteron. When Thalessa finds a tree infested by 

 this borer, she selects a place which she supposes to be 

 opposite the larva's burrow, elevates her long ovipositor 

 in a loop over her back, and places the tip of the ovipos- 

 itor on the bark of the tree. By raising and lowering 



l Thal$ssa lunator. 



"Tremex columba. 



