Other Common Names
Balloon Flies, Empids, Dagger Flies
Synonyms and other taxonomic changes
Marshall
(1) states that family may be polyphyletic--some groups more closely related to Long-legged Flies,
Dolichopodidae.
Sometimes spelled Empidae.
Explanation of Names
From genus
Empis, which is from New Latin (Linnaeus, 1767) from Greek, εμπισ (εμπιδ-), "a mosquito, gnat, larva of the gadfly"
(2).
Numbers
63 Nearctic genera.
Arnett lists 728 species for North America
(3).
Identification
"Empididae are 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."—Canadian Biodiversity Website (see Internet Sources, below).
Summary of characters:
thorax typically robust (humbpacked), abdomen typically tapered
coloration dark to black, sometimes yellowish or brown, not metallic as in the allied
Dolichopodidae (3)
legs slender, sometimes raptorial (modified for predation)
distinct "neck", proboscis often long, pointed
third antennal segment usually rounded, with a terminal style (hair-like process)
(4)Food
Tiny insects, and occasionally nectar as well. Larvae often feed on decaying vegetation or organic matter in the soil, some may be predatory.
Life Cycle
Larvae found in a variety of situations--aquatic, semiaquatic, in dung, in bird nests, among roots and fungi
(3).
Remarks
In mating swarms, males fly up and down in a sort of dance. They have captured an insect and wrapped it in silk, and hold it as an offering for females. Females seem to choose the male with the most enticing prey offering. Writers have recorded some instances of individual males cutting corners and offering only an empty ball of silk.
Male with "nuptial balloon"
"About swarming:
1. 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.
2. Different species swarm at different times of day. Some may swarm during the whole day, others maybe only for an hour at dusk, etc.
3. 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).
4. Nuptial gifts are not known for all mating dance flies. They are mostly found in the Empididae Empidinae (in genera like Empis, Rhamphomyia and Hilara) (the latter including the balloon flies)." Paul Beuk.
Print References
Marshall, pp. 399-400, photos, pp. 460-461
(1)
The Century Dictionary, entries for
Empidae, Empis +
(2)
