4 JouRNAi/ New York Entomological Society. [Voi. xxi. 



tions of aquatic insects are concerned with the respiratory system. 



Current is an important factor of aquatic environments which 

 finds its terrestrial counterpart in winds. That it is a very important 

 factor is shown by the numerous devices aquatic insects have to keep 

 their position and it varies from nothing in puddles to the rush of 

 Niagara. 



Food is a factor which is always both important and variable. 

 It is, however, a secondary factor in that, whatever the food habits 

 of the .insects may be, the analysis always leads us back to plants which 

 have their own primary relations to the organic factors of the en- 

 vironment. 



Enemies are also important and variable. The abundance or 

 absence of fish in a pool will go a long way toward deciding whether 

 mosquitoes will breed there or not. 



Summarizing the factors of aquatic environments with respect 

 to their effects upon the distribution of insects: Humidity is im- 

 portant only in the case of salty water and where there is a great 

 decay of humus as in peat bogs. Temperature is probably only 

 slightly more important. Light is probably important chiefly on 

 account of its influence upon vegetation, hence food. Oxygen would 

 seem to be of great direct importance. It should be noted in this con- 

 nection, however, that many of the insects which live in the water 

 breathe atmospheric air. Finally, among the inorganic factors cur- 

 rent is not only of direct importance but has an additional indirect 

 effect through its influence upon the oxygen content of the water. 

 The organic factors of food and enemies are, of course, of prime 



importance. 



— ■ ^ > 



RELATIONS OF TRICHOPTERA TO THEIR 

 ENVIRONMENT. 



By Chas. E. Sleight, 



Ramsey, N. J. 



Trichoptera are almost exclusively confined to aquatic environ- 

 ments during the larval and pupal stages. The larvae of one species 

 of Limnephilidse is reported to live in mosses at the roots of trees 

 but the group as a whole is typically aquatic. As far as I know, 



