THEIR RELATION TO EACH OTHER 121 



like a little borer, at others it is long, slender and flex- 

 ible, like a hair or bristle. Many of these elongated 

 types are found among species that attack boring 

 insects and some are quite capable of piercing deeply 

 into woody tissues. Excellent examples of this type 

 are found in the species of Thalessa, which expand 

 nearly two inches and have ovipositors almost or quite 

 four inches in length. These are parasitic on boring 



Fig. 60. — Pimpla conquisitor; a common parasite, with its lar\'a and pup 



larvce of the genus Tremex which live in burrows in 

 the trunks of maple and other trees. In some way 

 these huge parasites seem able to recognize infested 

 trees and to locate, at least approximately, the bur- 

 rows in which the borers are working. Then the long 

 ovipositor comes into play, and by a unique mechanical 

 contrivance the slender, bristle-like structure is forced 

 into the solid wood for sometimes its full length before 

 the desired burrow is reached and an egg can be de- 

 posited. It would be asking too much that the ovi- 

 positor should hit the exact point where the borer 



