56 



ZOOLOGY. 



lark). The cuckoo's egg is generally hatched by the 

 foster parent, and the true young often do not come 

 out from the egg, owing to lack of warmth; or, if 

 hatched, they are thrown out later on by the much 



Fig. 34.— The Cuckoo {Cfuculus canorus). 



larger, rapidly developing young cuckoo. Every 

 cuckoo, therefore, is so far harmful that it costs the 

 lives of several insect-eating birds. But it far more 

 than compensates for this by destroying insects. 

 It is especially beneficial to fruit-tree culture and 

 forestry, since it eats an enormous number of cater- 

 pillars ; but in late summer it comes frequently from 

 the woodland into the fields, and then eats the cater- 

 pillars of the cabbage white, cabbage moth, and 

 silver Y moth, surface caterpillars, and the larvae of 

 the turnip saw-fly. It also devours mole-crickets 

 and (naturally in the spring) cockchafers. 



