Prey size selection by Orthemis ferruginea (Fabricius) larvae (Odonata: Libellulidae) over mosquito instar

摘要: We investigated larval dragonfly predation in the lab using mosquito larvae and pupae as prey. Three variables were studied: predator size, prey stage and light/dark conditions. Prey stage was divided into three groups: first and fourth instars, and pupae. Results indicate that number of prey eaten was related to both predator size and prey stage (instar/pupa). Larger dragonflies ate more mosquitoes but did not show any preference. Smaller dragonflies ate preferentially fourth-instar mosquitoes. In this way, size-selective predation appears to be tied to the predator size. Light and dark conditions in general did not affect the number of prey eaten. We suggest three hypotheses to explain heavier predation on fourth-instar mosquitoes by smaller predators: a) major movements due to their size and stage, b) predators can detect them more easily because of prey size and shape, and c) a combination of both mechanical and visual cues.