I4 6 NORTH AMERICAN DIPTERA. 



The family Simuliidae, comprising about seventy-five 

 described species, is one of the best known popularly 

 among diptera, on account of the troublesome character 

 of the flies, which are scarcely less annoying than the 

 true mosquitoes; they rarely exceed five or six mm. in 

 length, usually not more than three or four, and will be 

 immediately distinguished from the mosquitoes by their 

 thick-set appearance, their shorter legs, their shorter 

 proboscis, and less slender antennae. In the southern 

 States they are known as ' buffalo gnats' and 'turkey 

 gnats', and sometimes occur in almost incredible num- 

 bers ; cattle when attacked by large numbers are driven 

 almost frantic, and will seek to evade them by rolling in 

 the dust, rushing about, or going into the water. When 

 the flies are numerous they will almost literally cover the 

 cattle, especially seeking the openings of the body, en- 

 tering the nostrils and the ears, the margins of the eyes, 

 where they will actually lie piled upon each other. When 

 very numerous they will produce an inflammatory fever, 

 frequently terminating in death. Infants have been 

 known to succumb to their bites. The well known Euro- 

 pean species is 5*. columbaczense , w r hich during some sea- 

 sons in the regions of the Danube costs the death of many 

 cattle. 



The larvae are very interesting creatures; they are 

 aquatic, living most frequently in mountain streams, on 

 stems of plants, or stones, where they form for themselves 

 elongated cocoons, opened above. In the open end of 

 these cocoons the pupae ensconce themselves with the an- 

 terior part of the body naked and free, from which ex- 

 tend eight or sixteen very long, slender, threadlike 

 breathing tubes. The perfect insect escapes under water 

 and comes to the surface. The larvae are soft-skinned, 

 thickened at the extremities, with a cylindrical head, 

 two pairs of eye-spots ; on the first thoracic segment there 



