INSECTS BENEFICIAL AND BEAUTIFUL 247 



I was watching, hunt over the surface inch by inch for 

 a likely place to drill ; but, after about an hour's search, 

 she flew away. Certainly nothing I have ever observed 

 has so impressed upon my mind the marvelous perfection 

 of Nature's mechanisms and the completeness with which 

 every darkest nook and corner of her domain is guarded. 

 A horntail, Tremex, bores deep into the tree and deposits 

 her egg. Who would think that any harm could reach it 

 there? But the ichneumon fly is armed and equipped for 



FIG. 102. BLACK THALESSA 

 d, drill ; ov, ovipositor. (-& natural size) 



her task. Her egg hatches in the burrow of the Tremex, 

 the young ichneumon finds the wood-boring larva, lives as 

 a parasite upon it, and, finally, after completing its trans- 

 formations, emerges as the ichneumon fly in the picture. 



There are more than a thousand genera of ichneumon 

 flies, with, of course, a great many more species, and if 

 the Tremex larva is not safe in the heart of a maple tree, 

 what must be the fate of the thousands of larvae that feed 



