Effects of pool depth and risk of predation on oviposition habitat selection by temporary pool dipterans.

Natural selection should favor females that oviposit in sites providing the best available conditions for her progeny. In temporary pools, two important conditions include risk of desiccation and risk of predation to larvae. In an artificial pool experiment, we compared oviposition responses of two dipterans, Culiseta longiareolata Macquart (Culicidae) and Chironomus riparius Meigan (Chironomidae), in very shallow pools that, if left to dry, would not have had a long enough hydroperiod for larvae to complete development, versus deeper pools that would have a sufficiently long enough hydroperiod for development. Water depth was crossed with the presence or absence of the predatory backswimmer Notonecta maculata F. (Hemiptera: Notonectidae). Oviposition patterns were consistent with larval vulnerability of the two species to predation by N. maculata. C. longiareolata, whose larvae are highly vulnerable to predation, strongly avoided ovipositing in pools containing this predator, whereas C. riparius, whose larvae are considerably less vulnerable, did not display oviposition avoidance. Pool depth did not affect oviposition habitat selection in either dipteran.