Trichome Removal by Hitchhikers in Two Leaf-cutting Ant Species (Hymenoptera: Formicidae)

Abstract

Despite the known evidence that hitchhiker ants protect workers against attack by phorid parasitoids, several alternative hypotheses are suggested for the occurrence of hitchhikers on leaf-cutting ants. One hypothesis suggests that hitchhikers clean leaf fragments and remove pathogens. We hypothesized that hitchhikers can act in the removal of leaf trichomes. Activities of hitchhikers (HH) are reported based on three laboratory and eight field colonies of leaf-cutting ants (Atta spp.). We evaluated whether the presence of trichomes increases the frequency of HH in leaf fragments transported to the colony. Furthermore, we evaluated if fragment size and the time that the fragment remains in the foraging arena could influence HH frequency. The removal of trichomes by HH of laboratory colonies was recorded on video. Hitchhikers were more frequent in fragments with trichomes in both laboratory and field colonies. In the field, the distance from the foraging site did not influence the amount of HH. The proportion of HH in laboratory, however, was most frequent only during the first hour of foraging. The presence of HH is correlated to the size of fragments. We also observed removal of trichomes as an additional role of hitchhikers.