52 BIRDS IN THEIR RELATIONS TO MAN. 



destructive to cultivated crops appears to be the little Hessian 

 fly (Cecidomyia destructor), often so serious an enemy to wheat. 

 The adult is a small gnat-like creature whose eggs are de- 

 posited on the blades of growing wheat, the resulting larvae 

 absorbing the sap of the plant and dwarfing or destroying it. 

 Closely related species attack the heads of clover and of 

 wheat. There is no doubt that great numbers of these flies 

 are devoured by swallows, swifts, and nighthawks during the 

 aerial evolutions of these birds. 



The long-legged crane-flies of the family Tipulidce are often 

 found in birds' stomachs. The adults of these insects appear 

 in spring, often in great numbers, and deposit their eggs in 

 grass-lands. A short time later the eggs hatch into small, 

 blackish, footless grubs, that feed upon grass-roots and decay- 

 ing vegetable matter. When full grown they are about an 

 inch long and of a grayish-black color. They now change 

 to pupae, to emerge as adult flies a fortnight later. The larvre 

 sometimes do serious injury to meadows. 



The Coleoptera, or sheath-winged insects, form the immense 

 order which includes the beetles. The front wings are hard- 

 ened into horny cases which cover and protect the membranous 

 second pair, the mouth parts are formed for biting, and the 

 transformations are complete. In the larval state the beetles 

 are commonly called grubs. A typical example of a beetle is 

 illustrated on the opposite page. Many beetles are destructive 

 to vegetation, a few live on decaying organic matter, and some 

 prey upon other insects. 



The tiger-beetles form a distinct family (Cicindelidce), the 

 members of which devour many other insects, being pre- 

 daceous in both the larval and adult states. These beetles 

 are often brightly colored and marked with distinct spots. 

 They are abundant in sandy situations and may be seen 

 commonly along lanes and roads or by the sides of streams. 

 Many of them are eaten by certain kinds of birds. 



The ground-beetles of the family Carabidce form an im- 



