23 
Number and General, Distribution of Species 
There are about sixty-five species of this genus in the world. 
Twenty-five of them have been found in North America and fif¬ 
teen in the United States. Nine species are known by us to occur 
in Illinois, and a possible tenth species is represented by an un¬ 
identified larva found in Vermilion county, Illinois, and also abun¬ 
dant in Yellowstone Park. (See Fig. i.) One American species, 
S. liirtipes, found in northern Illinois, occurs in Europe, and an¬ 
other, N. reptans, abundant thruout Europe, is reported from Green¬ 
land also, but not elsewhere from North America. It is to this 
latter species, indeed, that the spread of pellagra has been especially 
ascribed in Italy. 
Fig. 1. Simulium sp., head of larva from above. X 29. 
(Vermilion county and Yellowstone Park.) 
With a single exception, our American black-flies have, so far 
as known, quite similar habits. S. pictipes, found from New York 
to Illinois, Kentucky, Texas, and California, differs from the other 
more abundant species in the fact that it does not bite either man 
or beast. 
Injuries to Man 
Our more abundant Illinois species make a ferocious attack 
upon domestic animals and men, inflicting a bite much more severe 
than that of a mosquito, with more serious after-consequences. 
The stylets with which the wound is inflicted, are stouter, having 
more the form of a lancet, than the needle-like organs of the 
mosquito’s beak, and the venom injected into the cut from the 
salivary glands is a more efficient poison than the saliva of the 
mosquito. Men are less subject to injury than other animals, 
partly no doubt because their clothing protects them, partly be¬ 
cause they can put themselves beyond the reach of the pests, but 
apparently also because they are more resistant to the poison. 
