396 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 11 
After considerable reflection, the senior author decided that a study 
of the insect and its habits would have to be made and a test of the 
various insecticides instituted. 
Habits and Life-History 
The work began when the sprinkling filter still had a capping of ice. 
It was found that each piece of stone had upon it a more or less com¬ 
plete amorphous coating, which on examination proved to be exceed¬ 
ingly complex, being composed of a groundwork or matrix of gelatinous 
material in which and on which were found immense numbers of bac¬ 
teria, algae, protozoa (single celled animals), worms (unsegmented and 
segmented) and arthropods, principally Crustacea and insects. The 
sprinkling sewage filter fly was found in the maggot and pupa stages 
resting in this film with the breathing tube or tubes projecting through 
the film and securing atmospheric air. 
As soon as possible the junior author undertook the task of determin¬ 
ing the life-history and habits. This study continued through the 
spring into the summer. It was found that the principal species con¬ 
cerned was Psychoda alternata Say, but that during the latter part of 
April Psychoda drierea Banks appeared. It was found that with the 
opening of warm weather, the flies emerged from the over-wintering 
pupse and larvae in such numbers that for a period it was almost im¬ 
possible to breathe while working at the filter without getting some of 
them in the nose and mouth. After the over-wintering film had 
broken down and sluffed off and the warm weather film had begun to 
form, the flies rapidly disappeared until they became so scarce as no 
longer to form a nuisance. Records of the preceding summer (1917) 
show that with the advancement of the season the summer film be¬ 
comes heavier and the flies more abundant until in the month of Au¬ 
gust, when they reach a density greater even than that of the fore part 
of the warm season. 
It seems that the abundance of flies is correlated with the thickness 
of the film. A thick heavy film is normally accompanied by a tre¬ 
mendous breeding of the sprinkling sewage filter fly. 
A study of the food habits of the maggots showed that the feeding 
takes place in the film and that the food apparently consists of portions 
of the film. This habit of feeding, of course, serves to explain the 
increase in fly breeding which accompanies an increase in the thickness 
of the film. 
The eggs are laid upon the surface of the stone in irregular masses 
of from 30 to 100. The egg is about .36 mm. long and .17 mm. wide, 
oval in shape, white in color and resembles under a microscope nothing 
so much as a very small rice grain. With the exception of the yolk, 
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