1933 ] Tropisms Effecting Copulation in the Bed Bug 117 
then placed in a petri dish, allowing- space for free circula- 
tion of air and odor. A similar vial, not containing bugs, 
was placed in the dish as a control. Five vigorous males 
were put in the dish and left there for 30 minutes. Al- 
though the males were in close proximity of the females, 
they did not pay any attention to them but contrarily made 
attempts to mate with each other. This experiment was 
repeated several times with similar results. If there is a 
secretion, the odor of which serves to entice the male, one 
would expect this odor to be characteristic of the female 
only. As a result, one would presuppose that a few males, 
if brought near females, would cluster around them or 
around their container in the attempt to mate with them. 
This was not the case in the experiments. 
Again, three males were placed in a petri dish. Not long 
after, one female was placed together with them. All re- 
mained inactive because the room temperature was rather 
low. Upon increasing the temperature slightly, the bugs 
became more active. One male soon mated with the female, 
while the other male attempted to copulate with the third 
one. Contrary to expectation, the three males did not 
crowd around the single female as would have been the case 
had the female radiated some attractive odor. 
From the observations mentioned previously, the writer 
was inclined to believe that it is more likely that the sight 
of the moving image guides the male to the female rather 
than the odor. The following experiments were carried out 
to discover whether such was the case. 
A dead female was placed at the rear of a male and was 
left there for two or three minutes. The male did not ob- 
serve her. The dead female was then placed about 15 mm. 
in front of the male and left there for three or four minutes. 
Here, also, the male did not notice her. The female was 
then moved slowly with the aid of a fine camel’s hair brush, 
imitating the crawling of a live bug. The male, which had 
remained inert all this time “woke up,” extended his an- 
tennae in the direction of the dead female, and suddenly 
jumped upon her and made every effort to mate with her. 
Similar procedures were carried out several times and also 
at other occasions with different males, and very often sim- 
