86 INTERNAL ORGANS. 



Several species, well termed cuckoo-flies, thrust their 

 eggs into the nests or the bodies of other insects, or 

 animals, and have appropriate boring instruments for 

 this purpose. 



This is indeed one of the most singular circum- 

 stances in the economy of insects, and frequently leads 

 to no little disappointment, when collectors feed cater- 

 pillars for the purpose of breeding moths from them ; 

 for instead of the expected moth, a brood of cuckoo- 

 flies, whose maggots had been feasting on the body of 

 the caterpillar, make their appearance, and immedi- 

 ately pair and set out upon excursions for the disco- 

 very of other caterpillars, into which they may thrust 

 their eggs. 



