Age‐dependent foraging depths of two species ofNotonecta(Heteroptera: Notonectidae) breeding together in a small pond

Abstract

Clear plastic funnel‐traps were placed with their opening 1.5 to 72 cm below the surface in water ranging from 15 to 80 cm deep to examine the distribution of two Notonecta species in a small pond in Connecticut, USA. The results indicate that swimming depth increases with age in both species, but that at all ages N. insulata tend to forage in deeper water and at greater depths in the water column than N. undulata. N. undulata capture rates were highest in shallow water and in traps placed within 10 cm of the surface, while N. insulata comprised an increasing percentage of the Notonecta captured at greater pond and trap depths. It is suggested that an ontogenetic increase in foraging depth range provides older notonectids an expanded prey resource pool to meet their greater energy requirements. It is also suggested that N. undulata and N. insulata reduce interspecific competition by partially partitioning the prey resource pool along a water depth axis.