Contradictory effects of leaf rolls in a leaf-mining weevil

Abstract

Leaf rolls by herbivorous insects evolved in various lepidopteran groups, aphids, and some attelabid weevil species. Leaf rolls are known to have a positive effect on the survival of immature insects, protecting them from natural enemies such as birds, ants, predatory wasps, and parasitoids as well as environmental stress. On the other hand, leaf rolls are considered to have a negative effect on immature survival, attracting natural enemies because of their noticeability and subsequent learning or specialization. In this study, we directly tested the effects of leaf rolls using an attelabid species by comparing the fate of immature insects between artificial leaf rolls and unrolled leaves. The results showed the following positive effects of leaf rolls: avoidance of parasitism by eulophid wasps and avoidance of egg predation by unknown predators. On the other hand, a negative effect of leaf rolls was also detected, specifically and increase in mortality via leaf roll herbivory. This study indicated that leaf shelters are not only protective refuges but are also sometimes risky hiding places, although total survival rates increased in leaf shelters.