ARTHROPODA 



3 OI 



hours for hatching into the maggot stage. If food and temperature are favorable, 

 this maggot may grow to full size in a week, when it passes into the resting or pupa 

 stage, from which another week or more is required for the young fly to emerge. 



The eggs of mosquitoes are deposited in water, where they hatch into active 

 larvae called " wigglers." These breathe the air by means of a tube on the next to 

 the last abdominal segment. Their common position with the end of the tail at 

 the surface of the water is thus explained. The mosquito larva does not cease 

 to be active, but by a series of moults comes to the so-called pupa stage from which 



FIG. 142. 



PIG. 142. Stages in the development of the Bot-fly (Gastrophilus equi). From Parker and 

 rfaswell, after Brehm. a, adult insect; b, egg attached to a hair; c.d. and e, stages in^he development 

 of the larva. (See also Fig. 141.) 



by an early moulting the adult mosquito emerges, balancing itself on the floating 

 pupal skin until its wings are hardened sufficiently for use. See Fig. 143. 



The Hessian-fly deposits its eggs in the tissues of growing wheat and corn; the 

 clover-gnat and others produce galls which interfere with the growth of the plant, 

 often very seriously. In the case of the Hessian-fly great damage to the wheat 

 crop often results. See Fig. 144. 



The fleas are to be looked upon as degenerate. They are often placed in a 

 separate order (Siphonaptera) . The adults are external parasites without wings. 

 They are flattened laterally and thus pass readily between the hairs of the host. 

 The larvae are not parasitic, but live on decaying organic matter. 



