Effect of Larval Cannibalism on the Development and Reproductive Performance of Agromyza frontella (Rondani) (Diptera: Agromyzidae)

Abstract

In laboratory studies, we investigated the effects of cannibalism by the leafminer, Agromyza frontella (Rondani), of different instars on the subsequent development and reproductive performance of survivors. The treatments were one larva alone (CI), two larvae developing without cannibalism (CII), a first instar cannibalizing another first instar (11), a second instar cannibalizing a first instar (21), a second instar (22), or a third instar (23), and a third instar cannibalizing a second (32). In the 21, 23, and 32 treatments, cannibals completed larval development slightly faster than individuals developing alone in leaflets, although in 32 they suffered higher larval mortality, probably due to wounds incurred during interactions with the larvae they ate. The sex ratio differed between treatments but no consistent effect of cannibalism was observed. Pupal developmental time and the fecundity of mated females did not differ significantly between cannibals and noncannibals. However when cannibals successfully eliminated another larva from their leaflet their pupal weights and overall survival were higher than those of individuals developing two/leaflet without cannibalism, suggesting the most significant effect of cannibalism is to reduce exploitation competition by eliminating a competitor.