Species radiation of predatory empidoids (Insecta, Diptera) in lowland rainforest in northern Papua New Guinea

Abstract

Empidoid flies are among the most abundant flies in the lowland rainforests of northern Papua New Guinea. The Empidoidea, as considered here, comprise the families Hybotidae, Empididae, Atelestidae, Microphoridae and Dolichopodidae. Only one representative of the Empididae, a very abundant family in temperate regions, is known from Papua New Guinea. No Atelestidae nor Microphoridae are reported from the area. On the other hand, the Hybotidae and Dolichopodidae have radiated enormously. The stouter hybotids which catch prey with their raptorial hind legs in flight are present but not very common. The small leaf- and especially the soil-dwelling microhybotids are very abundant and very rich in species and they may well be the most important predators of micro-arthropods. The genus Elaphropeza (2–3 mm), the vicariant of the genus Platypalpus in temperate regions, with its numerous species, can be found running on leaves. The genus Nanodromia, known currently only from Papua New Guinea, also has numerous species that are found on leaves or on soil. They possess a piercing proboscis and raptorial front legs. Their small size (about 1 mm) suggests that they feed only on very small arthropods such as mites or collembolans. The dolichopodids occupy two major habitats. The larger, brilliantly green shining Sciapodinae are very commonly seen on leaves of bushes and trees. The other dolichopodids are generally found in humid areas such as the borders of pools, streams or in swamps. The genus Sympycnus, with its relatives, is probably the largest genus with more than 200 species still to be described. The males exhibit complicated secondary sexual characters which may reflect a fast radiation in a new environment (cf. species radiation in Hawaiian flies). Their biology and behaviour is unknown. Since some dolichopodid species are known to be predators of mosquito larvae, they warrant special attention.