1921] Riley: Responses of Water-Strider 253 
along in a direction more or less parallel with piles of leaves 
situated about a yard from the bank of the stream from which 
the water-striders came. They have been seen to enter such 
masses of leaves by way of the spaces left between the individual 
leaves of these bunches (Figs. 6, 7, 8, 9). Sometimes they 
attempted to enter the masses of leaves by means of inter- 
stices between the individual leaves so small that it was impossi- 
ble for them to walk in an upright position while doing so, 
or even after they had entered the interstices (Figs. 6, 7, 8, 9). 
It should be stated that, in course of time, these large bunches 
of leaves become very firm and compact (Figs. 6, 7, 8, 9). 
It was found that the insects overcame the difficulty of entrance, 
in some instances at least, by pressing the proximal portions 
of the legs so closely against their bodies that these appendages 
extended laterally from them and appeared to be almost in 
the same plane. In other instances the legs were raised until 
they were almost in the same plane as the bodies of the gerrids 
and slightly oblique from parallel to their long axes. These 
water-striders have been found under the bark of fallen, dead 
trees (Figs. 7, 8, 9) and in their interstices (Fig. 5) in spaces so 
restricted, that if the animals actually had not been observed 
to crawl therein, it would seem rather difficult to account for 
their presence in such situations. Often they have been taken 
from under heavy logs (Fig. 7, 8, 9) and driftwood, in such 
places where it seemed no insect could remain without being 
crushed. The act of crawling into locations of the various 
characters that have been indicated, as well as the act of 
staying there quietly, seems to be partially explained at least 
by their thigmotactic responses. There is some evidence that 
these gerrids may be negatively phototactic at this season; if 
this proves to be true, it would have to be taken into con- 
sideration in the final summing up. 
6. CONTACT RESPONSES AND DROUGHT. 
Some extended observations made, during the years 1911- 
1913 inclusive, on Gerris remigis, with reference to certain 
habitat responses, present additional information on the 
behavior of this species to contact stimuli. These observations 
were concerned mainly with the responses of the gerrids after 
their stream habitat had become dry (Figs. 8, 12), during 
