276 Annals Entomological Society of America ~ [Vol. XIV, 
Contact responses modified the phototaxis to some degree, 
due to the fact that a large number of gerrids were used in 
each trial, forty to be exact. 
When the experiments began, the animals were scattered 
about at various points on the surface-film. On the light being 
flashed into the aquarium, those gerrids which did not have 
their heads directed toward the lighted end of the aquarium, 
with four exceptions, immediately turned until they were 
standing with their heads oriented toward the source of illumina- _ 
tion and with the longitudinal axes of their bodies parallel with 
the long axis of the aquarium and also parallel with many of the 
rays emerging from the electric light bulb. The majority 
of them promptly strode toward the light and congregated 
at the positive end of the vessel. Others paused a few seconds 
before they moved toward the source of illumination. Seven 
appeared to be indifferent to the photic stimuli, in so far as 
locomotion toward the light was concerned. They moved 
about on the surface-film apparently without any reference 
to the source of illumination; or they remained almost station- 
ary; or they were busy cleaning their legs and antenne. A 
majority of the seven, during the locomotor movements, kept 
nearer to the negative than they did to the positive end of the 
aquarium. This suggested, perhaps, a tendency toward being 
negative in their responses with respect to the light. However, 
while conducting several other experiments, of a similar char- 
acter, it was noticed that just about as many individuals were 
near the positive as there were near the negative end of the 
vessel. These experiments showed that the larger number of 
the insects responded positively to the light and in much the 
same manner as was found to be the case in many former 
instances. 
After these preliminary trials and after similar responses to 
the above had been noted in a number of different trials, the 
gerrids were subjected to the influence of a moving light. 
It was moved slowly around the outside of the aquarium close 
to the glass sides and ends. The majority of the insects followed 
after the light. Some kept just behind it, or almost parallel 
with it—that is, opposite to the light—while others followed at 
a considerable distance behind the electric bulb. In a number 
of instances, gerrids followed the light, but kept at a distance 
of four to six inches behind it. However, there was very little 
