Other Common Names
Balloon Flies, Empids, Dagger Flies
Synonyms and other taxonomic changes
used to be treated in a broad sense to include all the Empidoidea except Dolichopodidae(1)(2)(3)
; here treated as defined in(4)(5)
, with the subfamilies Hybotinae, Ocydromiinae, and Tachydromiinae treated in Hybotidae; Brachystomatinae, in Brachystomatidae
~460 spp. in >30 genera of 3 subfamilies in our area(3)
, >3,140 spp. in >100 genera total(6)
Small to medium sized flies, usually elongated and mostly dark colored. They have a rounded head and a distinct neck, a large and humpbacked thorax and long tapered abdomen. The legs are slender and sometimes the front legs are raptorial, for grasping other insects. The proboscis is often long and pointed.(5)
small insects, and occasionally nectar; larvae often feed on decaying organic matter in the soil, some are predatory
Larvae found in a variety of situations--aquatic, semiaquatic, in dung, in bird nests, among roots and fungi(3)
In mating swarms, males fly up and down in a sort of dance. They have captured an insect, wrapped it in silk, and hold as an offering for females. Females seem to choose the male with the most enticing offering. Sometimes a male may offer just an empty ball of silk.
Paul Beuk on swarming:
You may have male swarms, female swarms and mixed swarms. In the case of the first two it may be that the other sex does not form swarms but joins the existing swarm for mate selection, or there are nearby separate swarms and specimens from one of those leave for the other to select a mate.
Different species swarm at different times of day. Some may swarm during the whole day, others maybe only for an hour at dusk, etc.
The location of the swarm is determined by markers. These may be very specific (under an overhanging branch in the sun, so the swarms may move with the sun) or rather 'generally defined' (along a slope, creating a very 'long' swarm, or over the water surface in a brook).
Nuptial gifts are not known for all mating dance flies. They are mostly found in the Empididae Empidinae (in genera like Empis, Rhamphomyia, Hilara) (the latter including the balloon flies).