Divided and undivided compound eyes in Ascalaphidae (Insecta, Neuroptera) and their functional and phylogenetic significance

The external morphology of the compound eyes of 13 species of the Ascalaphidae family (Insecta, Neuroptera) from Africa, Asia and Europe was studied in relation to the habitat, phylogeny and time of activity during the day. The six species with undivided eyes (Haplogleniinae) are nocturnal; four inhabit more or less open terrain, while two inhabit more or less dense vegetation. Of the seven species with divided eyes (Ascalaphinae), three are diurnal, one is crepuscular and nocturnal, and three are nocturnal. It was found that two of the diurnal species inhabit open terrain and open forest, and one inhabits dense vegetation; the crepuscular and nocturnal species inhabits open terrain; and two of the nocturnal species inhabit open terrain, while one inhabits dense vegetation. The results are discussed in relation to the hypothesis that divided eyes evolved from undivided eyes, originally serving as an adaptation to daytime vision in open terrain.