474 



NORTH AMERICAN DIPTERA 



The adults occur on ])irds and mammals. They are most frequently 

 found on birds, seldom flying. In the old world species of Hippohosca 

 are found on horses, camels, etc. and often occur in large numbers, as is 

 the case with the sheep tick, a wingless species occurring wherever 

 sheep are raised. 



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Hippoboscidae. — 1, Stilbometopa impressa; 2, Pseudolynchia maura; 3, Lynchia amer- 

 ■cana; 4, Ornithoica; 5, 6, Ornithomyia; 7, Ornithoctona erythrocephala. 



