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INSECTS 



clustering at the base of the horns of cattle. This is 

 an importation of comparatively recent date from 

 Mediterranean Europe, but it has spread in the few 

 years since its arrival throughout most of the United 

 States and into Canada. For a few years after its 

 first appearance it produced great alarm, and weird 

 stories were told of its destructive effect on cattle; 

 the least of which was that the flies attacked the horns 



FIG. 75. Horn fly: a, egg; b, adult; c, d, head and mouth parts. 



at base, laid their eggs there, ate off the root of the 

 horn and then penetrated the brain. As a matter of 

 fact much injury was caused to dairies from the abund- 

 ance of the flies, because they kept the cattle in a con- 

 stant state of irritation and therefore poor in milk flow. 

 But breeding was always in fresh cow manure, and at 

 no time did the insects get within the outer surface of 

 the animal in any stage. After two or three years of 

 alarm it was noticed that the flies lessened in number, 

 and finally became less abundant than the native 

 species, which it seemed at first fated to displace. 



