The Honey Bee and the Fly 



369 



gonorrhea, ophthalmia, and the eggs of tapeworms, hookworm, and a 

 number of other parasitic worms," they are certainly worthy of our 

 attention, and should be considered here, although it must not be thought 

 that flies are the only carriers of these diseases. It is especially inter- 

 esting to know that, while only about two persons die each year in the 

 United States from the bites of poisonous snakes and about one hundred 

 from the bites of rabid dogs, nearly 100,000 die annually from diseases 

 carried by flies. 



There are more than 43,000 different kinds of flies, gnats and mos- 

 quitoes which have been described in entomological literature, and there 

 is no telling how many more are still unknown. Tachina flies (Fi°-. 

 240), already described as killing grasshoppers, and Syrphus flies 

 ( ) which feed on insects are of real value to man, 



but nearly all others should be exterminated. 1 Over ninety per cent of 

 the flies found in and about homes are the regular typhoid flies. When 



Fig. 240. 



The Friend of Farmers. Red-tailed tachina-fly (Winthemia 4-pustulata.) a., 

 natural size; b., much enlarged; c, army worm on which fly has laid eggs, natural 

 size; d., same, much enlarged. (After S. Singerland.) 



it is remembered that the feet of these are furnished with claws for 

 climbing over rough surfaces as well as with two pads, the pulvilli, 

 covered with sticky, tubular hairs by which the animal can attach itself 

 to ceilings and glass surfaces, one can understand the excellent summing 

 up of what this means — that "No more effective mechanisms for col- 

 lecting dust could be designed than a fly's feet and proboscis (Fig. 216), 



*In the early part of 1923 hundreds of thousands of dollars were lost in the Santa Clara Valley. 

 California, by the larvae of Syrphus flies which could not be washed off the spinach leaves, thus 

 necessitating the closing of the canneries. Even friendly insects sometimes do much damage. 



