19 ANIMAL LIFE 



pigeon horn-tail (Tremex columba) (Fig. 117) deposits its 

 eggs, by means of a strong, piercing ovipositor, half an inch 

 deep in the trunk wood of growing trees. The young or 



FIG. 116. Caterpillar with cocoons of the pupae of ichneumon fly parasites, and 

 (above) one of the adult ichneumon flies. The lines indicate natural dimensions. 



larval Tremex is a soft-bodied white grub, which bores 

 deeply into the trunk of the tree, filling up the burrow be- 

 hind it with small chips. The Thalessa is a parasite of the 

 Tremex, and " when a female Thalessa finds a tree infested 

 by Tremex, she selects a place which she judges is opposite 



