wettable powder, B.H.C. 50% wettable powder and D.D.T. 50% wettable 
paste, at the rate of one pound per gallon of water, respectively. 
The mortality rate was found to be much higher and extremely rapid 
by this new method, using D.D.T., and was most effective when used 
as a wettable powder, 
A fifth and final experiment in this main series was carried 
out on October 4-8, 1958 (Table IV), using the same high-volume 
method but with the addition of combinations of D.D.T. and B.H.C. 
as well as the separate use of these materials. It was at this 
juncture that the improved method of counting bats flying out at 
night was devised, as described earlier under "Methods of Population 
Assessment." 
It will be observed that where the previous eradication of bats 
was high, the subsequent kill was reduced. However, results point to 
the need for making an accurate assessment of the bat population in 
each house before spraying is begun. The combined spray apparently 
gave no more convincing results, 
FOLLOW-UP 
In addition to the seven housés checked for bat population in _ 
the final spraying experiment, which was terminated in December, 1958, 
the other four houses were also checked at the same time, Further 
checks were made in the months of March, June and December, 1959, and 
March, 1960, again of all houses, including the untreated one, and the 
results were compared (Table V). 
TABLE V 
SUMMARY OF ALL BAT EXPERIMENTS AT CENTRAL EXPERIMENT STATION, 1958/59 


House Total number dead Total number of live bats flying outside 
Number bats (up-to-date) Dec. '58 Mar. *59 June '59 Dec, '59 Mar.'60 
1 79 32 17 16 40 38 
9 153"), 49 38 23 109 80 
10 ; 73 16 6 0 86 82 
3 179 O (bat 0 0 0 0 
proofed since 
Dec.) 
4 294 95 33 29 41 43 
t 150 12 0 0 13 0 
11 135 26 2 0 2 3 
2 138 2 6 1 4 3 
5 130 10 2 1 0 0 
3 (control) a 340 383 324 548 476 
a se SO A eee 
11 
