Ant-treehopper associations as visual cues for egg-laying Parrhasius polibetes (Lycaenidae), a facultative myrmecophilous butterfly

Oviposition is an important event for lepidopterans given that caterpillars have reduced mobility, and consequently cannot choose the place where they will live. While searching for an oviposition site, gravid females may rely on olfactory, visual, tactile and gustative cues, all of which usually originate from the host plant. However, the presence of natural enemies or mutualistic partners can also be used in host plant selection by egg-laying butterflies. In the Brazilian cerrado savanna, larvae of the butterfly Parrhasius polibetes feed on inflorescences of Schefflera vinosa (Araliaceae) and are facultatively tended by several ant species. Butterfly females prefer to oviposit on inflorescences occupied by aggregations of the ant-tended treehopper Guayaquila xiphias (Membracidae), near which the caterpillars benefit from increased survival. Given the conspicuousness of ant-treehopper aggregations, we investigated whether gravid butterflies would use their presence on foliage as a visual cue for oviposition. Field experiments were carried out using paired branches of S. vinosa containing dried ants and treehoppers. Butterfly eggs were counted and removed daily. The visual signal of ants plus treehoppers on branches resulted in greater oviposition activity by females compared to neighboring control branches without ants and treehoppers. The sole presence of ants or treehoppers, however, did not trigger a significant response by females. This reveals the importance of vision for oviposition site selection by P. polibetes, and also enhances the relevance of the combined visual signal from ants and treehoppers for egg-laying decisions by females. Olfactory and tactile cues, however, may also be used (FAPESP, CNPq).