Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Adult males and females of many insect species are expected to adjust their daily activity pattern in order to avoid stressful climatic conditions and increase the chances to encounter sexual partners. Using scan sampling methods associated with focal individual observations it was found that two satyrine butterflies of similar size and morphology, Hermeuptychia hermes (Fabricius) (Leptidoptera: Nymphalidae) and Paryphthimoides phronius (Godart), show completely different daily activity patterns on forest edges in southeastern Brazil. Hermeuptychia hermes presents one abundance peak in the morning and another in the late afternoon, while P. phronius abundance peaks in the mid-day, remaining stable until 1700 h. This difference is probably due to the occurrence of territorial behavior in the later species. The beginning of territorial defense by P. phronius males coincided with the time of new-born female activity. However, newly hatched females were not sexually receptive. The afternoon territoriality in male P. phronius may be in part related to mate acquisition. However, why the abundance of H. hermes decreases when the abundance of P. phronius increases is less clear.9Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)