1921] Riley: Responses of Water-Strider 279 
during migration by flight, probably finds bodies of water 
through the sense of sight. It should be remembered that the 
surface of water is an effective reflector, and large bodies of 
water, such as ponds and lakes, are likely to attract migrating 
gerrids. 
Other aquatic bugs, besides members of the family Gerride, 
belonging to a number of different genera of the order Heter- 
optera, exhibit responses to photic stimuli. It is of interest 
to notice that behavior of this character is not limited to a few 
groups, but, on the other hand, shows itself in many more or 
less divergent forms. It is not the intention to make an 
exhaustive enumeration of the genera and species that evince 
such responses, but rather to point out that these responses are 
a phase of behavior that should receive consideration in the 
study of the bionomics of this order of the Hexapoda. 
Comstock and Comstock (1895, p. 132) state that members 
of the family Belostomide respond to the stimuli from electric 
lights. Certain members of this group are apparently positively 
phototactic. From the context it is to be inferred that these 
observers probably refer to several genera of this family. It is 
well known, through the admirable investigations of Holmes 
(1905), that Ranatra fusca evinces positive phototaxis and that 
it is very strongly influenced by light. This paper by Holmes 
is an extremely suggestive and valuable one and for this reason 
it should be read carefully by all workers in animal behavior 
who are interested in the photic responses of aquatic Heter- 
optera. Because of its importance, certain quotations have 
been taken from it. Holmes (1905, p. 315) points out that: 
Light seems to dominate entirely this creature’s behavior when the 
phototactic reactions are once started. It does not manifest any fear 
or awareness of any object in its environment save the light which it so 
strenuously seeks. Its excitement increases the longer it is operated 
with. 
Ranatra fusca does not always exhibit positive responses 
to light. Under certain conditions it becomes negatively 
phototactic. Holmes (1905, p. 317) makes the important 
statement that: 
The negative reaction is associated with a condition of lowered 
phototonus. It is rarely shown except when the animal is in a condition 
of comparative sluggishness. When in great excitement, when its 
movements take place with quickness and vigor, Ranatra always shows 
a positive reaction. 
