RESULTS 
The first experiment (Table III) involved the low-volume spray- 
ing of eight houses, numbers 1, 2, 3, 5, 6, 7, 9, & 10, also the 
hand-operated high-volume spraying of house number 11, using four 
gallons of liquid per house, and the liberation of 48 B.H,C. smoke 
generators, "Gammexane No, 22", in house number 4, over the period 
March 17-19, 1958. House number 8 was the control. 
D.D.T. and dieldrin proved to be the most toxic, which fact 
was later confirmed at the end of the nine-month trial period when 
this particular mortality was found to represent approximately one- 
third of the total bat populations inhabiting the houses treated by 
these two insecticides. On the other hand, only one-fifth of the 
population was killed by the chlordane treatment and one-sixth by 
B.H.C, For reasons of cost and human safety in application it was 
decided to continue with D.D.T. only as a killing agent, experi- 
menting with other formulations of B.H.C. mainly as a repelling 
agent, as it had been noticed that this insecticide had the immediate 
effect of causing bats to fly out of the house, Also, this was more 
desirable as these bats are insectivorous and are considered biologi- 
cally useful. 
Houses for the following series of experiments were initially 
chosen in order of lack of success and in general the most success- 
fully treated houses were left as long as possible. Also, whenever 
it was practical the same successive chemical was used, that is, of 
course, limiting our choice to D.D.T. and B.H.C. 
The next experiment took place on July 15, 1958, and consisted 
of the low-volume spraying of houses 1 & 2 with the same quantity of 
liquid per house, but at four times the previous lowest dosage of 
B.H.C, wettable powder and D.D.T. wettable paste respectively. How- 
ever, even with the increased dosage, the kill by low-volume spraying 
was about the same, although still outstandingly better with D.D.T., 
and its residual effect lasted about two months, 
A third experiment consisted of the power-operated dusting of 
houses 9 & 10, on July 22, 1958, with B.H.C. in the form of 50% wettable 
powder and 5% dust. Dusting had little effect and in actual fact collection 
of dead bats was discontinued in house number 10 after ten days, and 
another treatment was tried, 
A fourth experiment followed on August 7, 1958, when the power- 
operated high-volume spraying of houses 4, 10 & 11 was carried out. 
Twelve gallons of liquid per house were used, composed of D.D.T. 50% 
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