Adult empidids are found in a variety of forest habitats, on the leaves of plants, on tree trunks, aquatic vegetation and also in stream beds and seepage habitats. Some species are associated with open areas such as grasslands, agricultural fields, marshes, coastal zones and beaches. Adults capture arthropod prey, including other
Diptera (including other empidids),
Hemiptera,
Homoptera,
Lepidoptera,
Trichoptera,
Thysanoptera,
Hymenoptera,
Neuroptera,
Plecoptera,
Ephemeroptera,
Coleoptera,
Collembola, and
Acari. Because of their predation they are important natural and
biological control agents of various pest insect species and as a group with a vast
species diversity they occupy a wide range of habitats. Some adult Empididae also visit flowers to obtain nectar. At least a few groups (
Iteaphila,
Anthepiscopus,
Anthalia,
Allanthalia and
Euthyneura) obtain all their protein needs by feeding on pollen. Larvae are generally found in moist soil, rotten wood, dung, or in aquatic habitats and also appear to be predaceous on various arthropods, particularly other Diptera larvae. Some Empididae, such as the
European species
Hilara maura, have an elaborate
courtship ritual in which the male wraps a prey item in
silk "balloon" and presents it to the female to stimulate copulation. It was first noticed that these flies carried "nuptial gifts" of silk by
Baron Karl von Osten-Sacken. Empididae show diverse mating systems, ranging from species in which males aggregate in mating swarms, and compete for choosing females to sex-role reversed species in which females do aggregate and compete for the attention of choosing males. In some species, such as the
North American species
Rhamphomyia longicauda, competition for the food provided by males is so strong that females have developed elaborate ornaments, including feathery "pennate" scales on their legs, darkened wings, and inflatable abdominal sacs that enhance their attractiveness. Across the group, nuptial balloons of species in the family range from small balloons containing large prey items (e.g.,
Empis aerobatica,
E. bullifera,
Hilara wheeleri), to balloons stuck to inedible dried prey items (e.g.,
E. geneatis), to completely empty balloons made of silk or saliva (e.g.,
H. sartor,
H. granditarsis). ==Evolution and systematics==