178 ; BLACK-FLIES. 
This species is found active during the whole summer and 
autumn, but only in certain places, which can, however, be 
very far from the breeding-places, and theseinsects must pos- 
sess some very powerful senses to detect their victims such 
long distances. 
In our lake regions we find a large number of streams 
that flow overrocky bottoms and are obstructed by floating 
grasses, and other submerged plants. When we see a place 

Fig. 146.—Simulium irritatum, n. s. Female and eggs. Greatly enlarged. Original. 
in which the water flows more rapidly than in others, we 
can be certain to find there the early stages of buffalo-gnats. 
By investigating the plants that cause an obstruction, we 
find large numbers of larve and pupz fastened to them. In 
the more central part of the state we find the adults, illus- 
trated in figs. 143 to 146, (the former showing a male, the 
latter a female) the most common species, while in the 
northern rivers the species illustrated in figs. 147 to 151 1s 
