Lekking in neotropical owl butterflies, Caligo illioneus and C-oileus (Lepidoptera : Brassolinae)

lWe demonstrate that the mating patterns of owl butterflies Caligo illioneu s (Cramer) and C. oileus (Felder) are leks. During 1993-1994, we recorded d istributions of male and female butterflies and larval hostplants in a lowl and Neotropical rain forest in Panama. Caligo illioneus males aggregated al ong forest edges and defended territories against both conspecifics and mal es of the related species C. oileus, which exhibited similar behaviors. Mal e perch sites were not associated with hostplant dispersion or the local ab undance of females. However, unmated female C. illioneus were observed to a rrive and copulate with males on territories that were located near where s treams intersected the roadway. We found some evidence that these leks over lap to form multiple-species aggregations. Caligo illioneus and C. oileus u sed the same sites at similar frequencies during 1993, a pattern that was r epeated during 1994. We could not detect if members of different species we re being attracted by similar environmental features or if they were effect ively attracting one another to the display sites. Independent of populatio n growth, the abundance of males at a particular site was correlated with t he abundance of heterospecific males during 1993, but this pattern was not confirmed in 1994, Overlap in the leks serves as evidence against a resourc e-based "hot-spot" hypothesis of lek formation.