1921] Riley: Responses of Water-Strider 259 
8. CONTACT RESPONSES AND DEATH-FEINT. 
Another form of response, related to contact, often is 
evinced by these gerrids and that is the death-feint. This 
frequently can be induced by gently stroking the dorsal sides 
of their bodies. Sometimes, merely touching the animals is 
sufficient stimulation to obtain the death-feigning response. 
In other instances, if they are picked up in the fingers, this 
response occurs. However, on other occasions, it is very 
difficult to elicit the death-feint and sometimes, no form of 
contact stimuli calls forth the response. Essenberg (1915a, 
pp. 399-400, 402) states that Gerris orba, a congener of Gerris 
remigis, feigns death, the response being very pronounced in 
certain individuals. The response can be elicited by contact 
stimuli. On arousing from the death-feint, it again can be 
induced by means of contact stimulation. The normal position 
assumed by Gerris remigis during the death-feint is for the 
body to lie flat against the substratum, where it becomes 
rigid. At such times the front pair of legs and antenne are 
stiff and stretched forward, while the middle and hind pairs of 
legs also become rigid and are stretched backward. The legs 
assume a position as nearly as possible in the same plane as 
that of the body and almost parallel with its longitudinal axis. 
The insects remain perfectly motionless during the response 
and may be handled without arousing them from the death- 
feint. They may be lifted by the posterior pairs of legs without 
these being bent. At such times, the entire weight of the body 
is supported by these legs. Often, on arousing from the death- 
feint, stroking the body and other forms of contact stimuli 
again induces the response. On the other hand, after the 
death-feigning response has continued for some time, contact 
stimuli, frequently, arouses the animals from it, as does dropping 
them onto the surface-film of water. 
Members of other families of aquatic Heteroptera besides 
Gerridz exhibit the death-feigning response, for example, the 
water-scorpions, Ranatra fusca (Holmes, 1906), Ranatra quad- 
ridentata (Holmes, 1907)—both of the family Nepida—Belo- 
stoma flumineum Say and Nepa apiculata Uhler (Severin and 
Severin, 1911), the former of the-family Belostomide and the 
latter of the family Nepide. Severin and Severin (1911a) 
again refer to the death-feigning instinct of Nepa apiculata. 
