Lepidoptera are of nocturnal origin but the transition to diurnalism seems to have happened many times and is still happening today.  A major reason for this transition seems to be the pressure exerted on nocturnal Lepidoptera by bats.  It seems that the main catalyst for the start of this process is the development of aposematism.  The main stumbling block for the completion of this process seems to be an inability in moths to adapt their classical nocturnal mate attraction systems using female pheromones to a diurnal lifestyle.  As a result a transitional nocturnal/diurnal stage is observed in some species where mate attraction still takes place at night but other functions are performed during the day.  A new mate attraction mechanism using male pheromones in conjunction with communal visual attraction systems has evolved in species that have completed the transition to diurnalism.

The sexual divergence of light-times for the species Acanthovalva focularia (Hübner) (Geometridae, Ennominae) and Phiala flavipennis (Wallengren) (Eupterotidae, Eupterotinae) is reported.  Adult behavior of Phiala flavipennis and the ennomine species Coenina poecilaria (Herrich-Schäffer), Acanthovalva focularia, Nassinia caffraria (Linnaeus), Nassinia Pretoria (Prout), Nassinia aurantiaca (Prout) and Biclavigera uloprora (Prout) and Biclavigera uloprora (Prout) are reported and discussed.