Family Hydropsychidae 



with the mouth. The mouth is composed of a network of silk 

 supported by arched bits of twigs. The larva remains hidden 

 in the funnel, watching for its prey to be caught in the open mouth. 

 The cases were preferably placed at the edge of slight depressions 

 in the rocky surface so that the tubuhir portion was protected 

 from the full force of the current. On the surface of a rock about 

 eighteen inches in diameter i66 of these nets were counted. The 

 larvae of one of the black (lies were very abundant in this stream 

 and were washed into the mouths of these nets and probably 

 formed the principal food of the Hydropsyche larvae. Therefore, 

 this is one of the few creatures which we know which helps to 

 reduce the number of black flies and it must therefore be con- 

 sidered as very beneficial to mankind. The family is a rather 

 large one and nearly thirty species are known to occur in this 

 country, about half of them belonging to the typical genus 

 Hydropsyche. Marrouema icivafifin Hngen is one of our hand- 

 somest species. Its wings are beautifully spotted and banded 

 with yellowish brown. It occurs from Canada south to Virginia. 



aoS 



