2l6 



SYSTEMATIC ZOOLOGY 



Fig. 218. Cecidomyia destructor, the 

 Hessian fly. I, adult insect ; 2, larva; 

 3, pupa; all enlarged. (After Ship- 

 ley and MacBride.) 



fluid substances. Thus we find larvae developing in caterpillars, 

 in mammals either on the skin, or under the skin producing 

 ulcers, in the nasal chamber, or even in the stomach. Others 

 grow in cherries and other fruits ; some occur in stagnant water, 



in sewers, in decaying animal or 

 vegetable matter, in the earth; and 

 the gall flies deposit their eggs on 

 plants, which develop galls about 

 them. The larvae of the Hessian 

 fly, Cecidomyia destructor (Fig. 218), 

 is very destructive to crops in the 

 United States, as it sucks the juices 

 from the growing stalks of grain. 

 The botflies of the horse and the 

 ox have very hairy bodies, so that 

 they look not unlike some of the 

 bees. 

 In the common horsefly it is only the female that bites, the 

 male being without any organs for piercing. The same is true 

 of the mosquitoes, whose wingless larva- (Fig. 219) can be seen 

 in great numbers in a body 

 of standing water in the 

 summer time ; here the 

 females become a veritable 

 pest in many countries and 

 also very dangerous when 

 we remember that one 

 genus, Anopheles (Fig. 

 220), is the agent in 

 transmitting the malarial 

 parasite to man, and that 

 infection with the parasitic 

 roundworm, Filaria, is 

 acquired in the same way ; 

 it seems, too, to be pretty 

 well established that yellow- 

 fever is likewise trans- 

 mitted by a mosquito of the genus Culex, or Stegomvia. as it 

 has more recently been called. In this same order we may 



FIG. 219. Culex. The adult male mosquito and 

 the larva. (Alter Guerin and Percheron, from 

 Parker and Haswell's Manual.) 



