88 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 12 



bodies buried in the film. When pupation has been completed the front 

 end of the pupal shell is burst open and the fly emerges. 



The insect is not a strong flier and its movements from the filter are 

 much influenced by the wind. It has the habit of resting on the under- 

 sides of the stones in the upper layers of the filter and upon the 

 sidewalls of the filter itself. The life cycle may be completed in the 

 summer in a minimum of a little less than 12 days. As a matter of 

 fact, a brood emerges during the summer about once each two weeks. 



Although larvae and pupse of this fly may be found throughout the 

 filter bed, they are most abundant in the zone which begins three inches 

 below the surface and ends about twelve inches below the surface. 



The abundance of larvae and pupae seems to be correlated with the 

 thickness of the film. A thick film means heavy breeding, a thin film 

 light breeding. During the winter and spring the film becomes very 

 heavy and consequently the pest is very abundant, in the fore-part of 

 the season. As the weather becomes warmer the filter unloads. Large 

 quantities of the film sluff off and pass out with the effluent, and a thin 

 film takes its place. This thin film gradually increases in thickness as 

 the summer goes by, until in the latter part of the summer it becomes 

 heavy and consequently develops a great abundance of flies. 



c ^o 



Fig. 4. — Diagram showing position of larva and pupa of the Sprinkling Sewage 

 Filter Fly in the film. A, Film; B, Stone; C, Larva; D, Pupa. 



Control 

 Practically all of the organisms composing the society of which the 

 Sprinkling Sewage Filter Fly is a part, can get along without atmos- 

 pheric oxygen for a longer time than it. Both the larvae and pupae 



