PARASITISM AND DEGENERATION 



191 



a Tremex burrow, and, elevating her long ovipositor in a 

 loop over her back, with its tip on the bark of the tree (Fig. 



FIG. 117. The pigeon horn-tail (Tremex 

 columbd), with strong boring ovipositor. 



FIG. lia Thalessa lunator boring After 



COMSTOCK. 



Fio. 119. The large ichneumon fly 

 Thalessa, with long flexible oviposi- 

 tor. The various parts of this ovi- 

 positor are spread apart in the fig- 

 ure ; naturally they lie together to 

 form a single piercing organ. 



118), she makes a derrick out 



of her body and proceeds with 



great skill and precision to drill a hole into the tree. When 



the Tremex burrow is reached she deposits an egg in it. 



