280 _ Annals Entomological Society of America  [Vol. XIV, 
He (1905, pp. 318-325) has recorded a number of other very 
singular facts with respect to the negative responses to light. 
This water-scorpion may become negative in its behavior 
toward photic stimuli through the agency of contact stimulation, 
but, strange to relate, the negative responses also may be held 
in check by the latter form of stimuli. Further, negative 
phototaxis can be induced by long exposure to strong light. 
In another interesting paper, Holmes (1907, pp. 160-161) 
directs attention to the fact that the young of Ranatra quad- 
videntata respond to light. In this connection, he states that: 
The reactions of young Ranatras to light are not nearly so vigorous 
and decided as those of the adult. A feeble positive phototaxis is man- 
ifested the first day after hatching and increases gradually as the insect 
grows older. Individuals a week old are very often found swimming on 
the side of the dish towards the light; if the dish is turned about they 
quickly swim again to the light side. When out of the water they are 
comparatively irresponsive to light—a fact in marked contrast to the 
behavior of the mature insects. 
According to this writer (1907, p. 163), Ranatra linearis, a 
European species, is positively phototactic and occasionally 
flies to lights during the night. Cole (1907, pp. 382-383) has 
not only substantiated a number of the experiments of Holmes, 
but in addition he (1907, p. 397). has shown that Ranaira fusca 
can discriminate between two lighted areas that are of different 
size, although the illuminated fields are of the same intensity. 
His experiments evidently prove that Ranatra fusca also is 
able to form images of ‘‘considerable definiteness.’’ De la 
Torre-Bueno (1914) has written a paper on phototropism, 
which is of value not only because of the discussions in it on 
the phototaxis of Heteroptera, but also because of the relations 
of these discussions to the light responses of aquatic Heteroptera 
in general. 
Many of the species of the family Notonectide are 
responsive to photic stimuli as Essenberg (1915) has dem- 
onstrated. Notonecta insulata Kirby, Notonecta undulata var. 
charon, Notonecta indica, and a species that was" not identified 
were all used, apparently, in Essenberg’s experiments. Noto- 
nectas evince a strong positive phototaxis (1915, pp. 385-386) 
to various kinds and intensities of lights. The positive photic 
responses are intensified by increases in temperature and 
increases in light intensities (1915, pp. 387-388). A sug- 
