Two Florida dragonflies of the family Corduliidae perform their territorial patrol flights at different times of the day. Epitheca Stella (Wmsn.) flies during the middle part of the day, as is the case with other species of the genus, but E. sepia (Gloyd) is on territory from late afternoon to dusk. The two species are similar in size, appearance and structure and fly during the same season, and the temporal separation of the territorial flights may be the only reproductive isolating mechanism between them.