74 DIPTERA OF MINNESOTA. 



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 

 tormented him in Labrador. In many places fishermen have to build 

 smudges to drive away some of these tormentors. * * * 



"All these insects have a very similar life history, and the one 

 given will apply to all. Their peculiar larvae live in swift currents of 

 creeks and rivers, where they feed upon very small aquatic animals, 

 diatoms, desmids, etc. To obtain this food they are equipped with 

 peculiar fans on their heads, which are constantly moving in the water, 

 thus creating a current toward the mouth proper, and the material 

 thus brought there is sorted by the other mouth-organs and either 

 utilized or repelled. The larvae living in such a swift current anchor 

 themselves by a peculiar sucking disk at the end of their body, and 

 by a tough silken line, and are thus kept in position, which is an 

 upright one, and one in which the face fronts the current. The 

 larvae breathe by means of a peculiar organ situated near the tail, 

 and the different species are distinguished by these breathing organs, 

 which are either very simple or are quite complicated. 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 



Fig. 62. 5. vittatunt . larger female, smaller male, to show markings. Lugger. 



end of the larvae can move about like the well known measuring 

 worms or geometers. Constantly feeding, these larv^ grow very 

 rapidly, and are soon ready to transform into pupae. But before 

 they can do so they have to construct some protection for the inactive 

 pupae, otherwise this would be swept away by the current. They con- 



