DIPTERA. 20I 



pond, and empty every rain barrel or other vessel which 

 might serve as a breeding-place. If draining is imprac- 

 ticable, covering the surface with a coating of oil will 

 kill the larvEe and the pupse. They are air-breathing 

 animals, and the oil film makes it impossible to get air 

 to breathe; they drown as you and I would if we were 

 shut off from air. Good ventilation will usually disperse 

 large numbers of them, which have the habit of collecting 

 about dwellings, porches, area-ways, and other sheltered 

 places. Mosquitoes are not strong on the wing, and a 

 stiff breeze often sweeps them out of their course. This 

 is especially true of Anopheles, the malaria disseminator. 

 Anopheles and the semi-domestic species, Culex pipiens, 

 have limited powers of flight and so must breed close to 

 their feeding-places, two hundred yards, in some cases 

 twenty-five feet will be found to be their limit. Adult 

 mosquitoes vary in their feeding 

 habits; some fly only at dusk, some 

 fly almost all night, hiding in dark 

 places or at the bases of rank-growing 

 grasses during the day ; and still other 

 species may be found abroad in the 

 daytime. 



As to the good qualities of the 

 beneficial fly families, much more Fig. 8s.-A Syrphid or 



■ 1 , • 1 , , ,1 • I- flower fly. (Kellogg.) 



might be said than there is space for 

 here. To them we are indebted for the destruction of large 

 numbers of wood-boring beetles (midas flies) ; of grass- 

 hoppers (bee flies and wasp flies) ; and the pollenation of 

 many plants (flower flies orSyrphids). (Fig. 85.) The 

 Tachina flies deserve special mention here. They are rather 

 heavy-bodied flies, with hairs generally more numerous 

 and longer than the hairs on the house fly's body; though 



