Holmes' Tropisms of Animals. 
19 
the reverse attitude. Hold the light in front of the body and the 
insect bows down in front in an attitude of abject submission, 
while if the light is carried behind it the insect elevates the anter- 
or part of its body and holds its head high in the air. These 
bodily attitudes are assumed with almost machine-like regularity. 
For each position of the light there is a corresponding position 
of the head and body. 
After a little Ranatra will follow the movements of the light 
by walking slowly and awkardly toward it, gradually increasing 
the vigor and rapidity of its response until it will rush toward the 
light with frenzied haste. It becomes oblivious to all else but the 
light which seems to dominate its behavior entirely. If the source 
of light gives off a good deal of heat the insect will continue to go 
toward it until overcome by the heat. I have seen Ranatras when 
nearly killed by the heat of the lamp toward which they were 
attracted, slowly drawing themselves with the last remnants of 
their strength a little nearer to the fatal source of light. 
Nothing could seem more mechanical or more obviously the 
result of domination by outer agencies than the phototaxis of this 
form. There are, however, some curious features of the behavior 
of Ranatra which are disclosed by other experiments and which 
indicate that this insect is something more than a mere “reflex 
machine.” If one eye is blackened over there is a strong tendency 
for the insect to perform circus movements toward the normal 
side. Frequently as the insect veers over toward the normal side 
in going toward the light and thus brings the unblackened eye 
more and more out of the region of direct stimulations, a point is 
reached where there is hesitation, moving this way and that, 
accompanied with increasing uneasiness and excitement as if exas¬ 
perated over its predicament. Sometimes the insect may get out 
of this situation by going completely around in a circle toward 
the normal side, or it may make a direct turn toward the blackened 
side and go toward the light. In several cases among Ranatra 
and Notonecta individuals which at first performed circus move¬ 
ments and succeeded in going to the light by a very irregular route 
finally came, after a number of trials, to go to the light in a nearly 
straight line. Other individuals went to the light in a nearly 
straight line from the first. In some cases covering all of one eye 
and all but the posterior face of the other did not prevent the 
