400 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 11 
Flooding Experiment Carried Out in Flower Pots 
Length of Time Flooded 
Condition of Larvse and Pupse 
Condition of Film 
16 hours 
Alive 
Alive 
18 hours 
Alive 
Alive 
22 hours 
95% dead 
Alive 
24 hours 
Dead 
Alive 
32 hours 
Dead 
Alive 
36 hours 
Dead 
Slight putrefication 
48 hours 
Dead 
Putrefaction 
This set of experiments was repeated three times with exactly the 
same results. It thus seemed that submergence for twenty-four hours 
destroyed 100 per cent of the larvse and pupae and apparently did not 
injure the film. 
Realizing that the results in the flowerpots might differ from results 
of the same treatment on the filter bed, we asked the Joint Sewer 
Committee to make the necessary preparations to submerge one 
quarter of the filter bed involving somewhat less than half an acre. 
Although the problem of blocking off the drainage pipes from this 
section was a difficult one it was undertaken and carried out. The 
entire supply of effluent was turned into one dosing tank and run into 
this quarter of the filter. In three hours and thirty minutes after 
starting, this quarter of the bed was submerged. The submergence 
was completed at 1.30 p. m. and the water was maintained on the bed 
continuously from that time until 1.30 the following day, when the 
sewage was turned off this quarter entirely into the other parts of the 
bed. In about two hours after the sewage was turned off this quarter, 
some of the stops were knocked out of the drains and samples of the 
effluent caught as it came from the treated section of the bed. Thou¬ 
sands of larvse and pupse, particularly larvse, were swept out and careful 
examinations of samples showed that 100 per cent were dead. For an 
hour after this time the senior and junior authors watched the effluent 
as it came from the filter into the final Imhoff tank. Constantly 
during this period the water swept by well filled with these dead larvse 
and a smaller number of dead pupse. In no case were any found to be 
alive. This submergence was completed on Saturday afternoon. 
The filter was allowed to stand without water over Sunday. The 
following Monday the stoppings were all removed and the sewage 
turned back on this quarter of the bed as usual. Tests of the effluent 
of the filter for a week afterward by the manager of the plant, Mr. 
John R. Downes, indicated that the activity of the film had been in 
nowise impaired. 
It thus seems that the sprinkling sewage filter fly, Psychoda alternata, 
and its less important relative, Psychoda cinerea, may be destroyed by 
