October, ’18] HEADLEE AND BECKWITH: SPRINKLING FILTER FLY 399 
a trial of increased strength. Similar tests were made with 15, 30 and 
50 pounds per acre. The kill being still incomplete, the 50 pounds per 
acre treatment was repeated three days in succession and gave a kill 
of about 85 per cent of the maggots. Many of the maggots appeared 
in the final tanks alive and fully 15 per cent remained in the filter bed 
unharmed. The film was considerably injured by the heavier treat¬ 
ments, particularly the last one. 
Thus it is seen that the tests of chemical substances brought forward 
nothing of a satisfactory nature for the control of the sprinkling sewage 
filter fly. 
Flooding 
The senior author early in the study brought into the laboratory 
some of the filter stones and, desiring to keep the material on them 
alive until the following day, covered them with tap water. When he 
undertook to resume examination of the film on the following day, he 
found that all of the maggots of the sewage filter fly were dead. This 
accidental observation, when correlated with the fact that the breath¬ 
ing tubes of the maggots and the pupae projected through the film in 
such a way as to enable the creatures to obtain atmospheric air, led 
promptly to the suspicion that the species could be destroyed by drown¬ 
ing. 
Examination of the film for the purpose of determining the effect 
of the various chemicals upon it indicated that the other animal forms 
at least were such as to be resistant to such a process, and the bacter¬ 
iological studies made by various sewage disposal students indicated 
that the bacteria should be able to resist flooding for a considerable 
period of time. It was therefore determined to test submergence as a 
possible method of destroying the sewage filter fly. 
Accordingly, a series of experiments were undertaken by the junior 
author to test out this method of destruction. In these experiments 
the filter stones with their covering of film were taken directly from 
the filter bed and placed in 6-inch burnt-clay non-glazed flower pots, 
the drainage hole of which was stopped up. An average of about one 
quart of stone was placed in each pot, and the pots set into the bed so 
that their tops were practically flush with the surface. As the spray 
played, the pots became filled with water and the stone contained in 
them completely submerged. The length of time was the only variant. 
After the treatment was completed, the stones were examined for 
signs of life in the larvae and pupae. The condition of the film was 
determined by making a smear on the glass slide and examining it 
under the microscope. The active forms of protozoa were used as an 
index to the life of the film. Putrefication was determined by odor 
only. The following table will set forth the detail of the results: 
