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. 
Fie. 117.—The pigeon horn-tail (Tremex 
columba), with strong boring ovipositor. 
Fie. 118.—Thalessa lunator boring.—After 
CoMsSTOCE. 
118), she makes a derrick out 
of her body and proceeds with 
Fie. 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. 
great skill and precision to drill a hole into the tree. When 
the Tremex burrow is reached she deposits an egg in it. 
