BLACK-FLIES. 179 
the common one. This latter species is a great tormenter to 
humanity, and the proverbial patience of fishermen is 
severely taxed by their bites. In the northern part of Min- 
nesota this species is called the “black-fly.” Their bite is 
very severe, and the experience narrated by A.S. Packard 
would apply to this insect as well as to the one that tor- 
mented him in Labrador. In many places fishermen have to 
build smudges to drive away some of these tormenters. As 
both these kinds seem to be undescribed, the name S. irrita- 
tum 1s proposed for the first and WN. 
tribulatum for the second species. 
All these insects have a very 
similar life-history, and the one 
given will apply to all. Their pecu- 
har larve (fig. 147) live in swift 
currents of creeks and rivers, where 
they feed upon small aquatic ani- 
mals. To obtain this food they 
are equipped with peculiar fans on 
their heads, which are constantly 
moving in the water, thus cre- 
ating a current towards the mouth 
proper, and the material thus 
brought there is sorted by the oth- 
er mouth-organs and either utilized 
or repelled. Thelarvee living in such 
aswift current anchor themselves 
by a peculiar sucking-disk at the 

Fig.147.—Simulium tribulatum, end of their body and by atough sil- 
Orginal oY enlarged. ken line, and are thus kept in posi- 
tion, which is an upright one, and one in which the face 
fronts the current. The larvee breathe by means of a pecul- 
lar organ situated near the tail, and the different species are 
distinguished by these breathing-organs, which are either 
very simple as the one shown in fig. 147, or are quite com- 
plicated. Only one leg is found upon these strange looking 
beings, and this is found upon the first joint, yet by means 
of it and the sucking disk at the tail end the larve can move 
about like the well-known measuring-worms or geometers. 
