Family Gerridae.

Species of the genera Limnogonus, Mesovelia, and Microvelia were commonly present on the surface film of the more permanent ground pools at Palmalmal. Unfortunately, there was insufficient time available to carry out feeding experiments with these insects before my departure from New Britain.

Text-fig. 6.—Limnogonus fossarum.

A large gerrid, Limnogonus fossarum (Fabricius, 1775) (Text-fig. 6), was observed in the field sucking the body juices of a newly-hatched imago of Culex fraudatrix Theobald, 1905. Other specimens of this insect were seen to attack late instar anopheline larvae. It appears, however, that various terrestrial and aerial insects that have fallen into the water provide the main source of food for Limnogonus and other genera of water-striders.

It was noticed that pools with heavy populations of gerrids never contained many anopheline larvae. This circumstance could not be ascribed solely to the presence of the water-striders, for other aquatic predators of proven value as mosquito enemies were always present as well. Nevertheless, by reason of the facts that Gerridae are of surface-feeding habit and that Limnogonus was actually observed to destroy larval and newly-emerged anophelines, it appears likely that members of this family are of some importance as mosquito enemies.