xxxiii, '22] ENTOMOLOGICAL NEWS 87 



has been accumulated in connection with their food habits. In 

 this short paper it is the intention to direct attention to certain 

 different kinds of food used by Gcrris rcmigls Say and Gcrris 

 marginatiLS Say while in captivity in aquaria. 



In my habitat studies of these two species, it has been noticed 

 that Gcrris rcuiiyis feeds on a variety of insect food, and the 

 same is true with respect to Gcrris inaryinatits. Additional 

 information was obtained on this tendency toward omnivorous 

 feeding, while studying water-striders during confinement in 

 aquaria. Many observations were recorded \vith respect to the 

 kind of food that was eaten. 



It was found that both Gcrris rcinii/is and Gcrris marginatus 

 will feed on the pupae and adults of Gulc.r sp., small and large 

 species of Tipulid flies, Syrphid flies. Musco doincstica, Chiron- 

 oinns sp., Tabaiuts sp., and Drosophila anipclophila. 



Gcrris rcmiyis is a more vigorous and daring feeder than is 

 Gcrris marginal us and has been observed to feed on Notonccta 

 nndnlata, Chrysopa sp., Calopteryx inacitlata, Ifctacrina aincr- 

 icana, and Arctocorixa sp. 



My observations seemed to indicate that both species of 

 water-striders are flesh feeders, but when they have been de- 

 prived of food for several weeks, they are, apparently, not 

 particular as to the character of their food. Both Gcrris re in it/is 

 and Gcrris marginatus were noticed as they were feeding on 

 the soft parts of banana fruit and also on the inner softer 

 portions of the skin. Several persons in the laboratory saw 

 this unusual form of response. During confinement in aquaria, 

 both species suck the juices of freshly killed snails, Pliysa sp. 

 and Planorbis sp. and also small pieces of fresh beef. 



Gcrris remit/is and Gcrris margmatus display cannibalistic 

 responses in their own habitat. When their brook habitat so 

 shrinks in volume, during a drought, that then- remain only 

 a few small isolated pools in the bed of the stream, thus de- 

 priving the gerrids of food, they will attack members of their 

 own species. This somewhat unusual respond- has been oh 

 served to nrcur in aquaria. Gcrris remit/is not infrequently 

 seizes and sucks the body juices of weaker individuals of its 

 own kind and also of Gcrris marginatus. Gerris iiniryinatiis 

 has been seen to feed on the weaker members of its own species. 



