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- 



turn is proposed for the first and S. 

 tr'ihulatum, for the second species. 

 All these insects have a very 

 similar life-history, and the one 

 given will apply to all. Their pecu- 

 liar larva- (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. The larvae living in such 

 a swift current anchor themselves 

 hy a peculiar sucking-disk at the 

 Fig. \.i.i.-simHii,im Mhahihun. end of their bodj' and by a tough sil- 

 or^^iai""- ""'""'"^ '"'"''^'''- ken line, and are thus kept in posi- 

 tion, which is an upright one, and one in which the face 

 fronts the current. The larvae breathe by means of a pecul- 

 iar 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 larvae can move 

 about like the well-know^n measuring-worms or geometers. 



