Overview
Here, the family 'Empididae' is treated in a more recent restricted sense, or Empididae s.s. Most previous accounts (including the current catalogue to the Australian fauna, Smith 1988, and Nearctic key by Steyskal & Knutson 1981) treat Empididae in a broader and paraphyletic sense (Empididae s.l.), to include what are now recognised as the families Empididae, Hybotidae, Microphoridae and Atelestidae (not known to occur in Australia). See Chvala (1983), Sinclair (1995) and Cumming and Sinclair (2000) for further discussion.
Taxa that superficially might be confused with Empididae include the family Asilidae (which have a prominent ocellar tubercle between the deeply excavated vertex, strong setae or mystax on the clypeus, and a large anal cell cup that nearly reaches the wing margin), some subfamilies of the Bombyliidae (also with a large anal cell cup that nearly reaches the wing margin), and some Platypezidae (these have a 3-segmented arista, rather than the 2-segmented style of most Empididae).
Adult Empididae are often found alongside streams in various forested habitats, on leaves and seeps, although some taxa are associated with heathland vegetation or littoral habitats. Adults are predacious, and take various arthropod prey, although some visit flowers to take nectar, and some are known to feed on pollen (Chvala 1976).
This family contains wingless species.
Description
Body length 2.0 to 12.0 mm. Adults generally of stout build, and usually with brown to black and sometimes yellow cuticle (rarely metallic coloured), often with brown pruinosity. The head, thorax and legs often with abundant black setae and vestiture. Head usually spheroidal and narrower than width of thorax and with large compound eyes, sometimes dorsally holoptic in males. Antenna with basal flagellomere (postpedicel) 1-segmented, and usually with 2-segmented, apical stylus. Proboscis short to elongate, often sclerotised and pointed, labrum usually armed at apex with epipharyngeal blades; palpus 1-segmented. Thorax stout and subrectangular in dorsal view, often with abundant chaetae. Legs varied in length, strength and armature, sometimes sexually dimorphic, empodium usually setiform, pulvilliform in some aquatic groups. Wings of varied shape and size, costa often continuing in reduced thickness around the posterior margin of wing, Rs originating well distad of level of origin of crossvein h, R4+5 usually forked, but sometimes unbranched, and cell cup closed, never reaching wing margin. Abdomen subcylindrical, usually elongate, and some tergites with abdominal plaques laterally. Male terminalia usually unrotated. Female oviscapt usually with stout dorso-apical spines.
The larvae are maggot-like and predacious. They live in moist soil, decayed wood and other vegetation, dung, and aquatic habitats (see Dyte 1967). Very little is known of immature stages in the Australian fauna.
This family contains wingless species.
Distribution
The Empididae comprise the following six subfamilies: Oregetoninae, Empidinae, Hemerodromiinae, Clinocerinae, Ceratomerinae, Trichopezinae, and Brachystomatinae (possibly not in Australia). Only a small fraction of the Australian fauna has been described and many new genera await description. Some of the more prominent taxa are treated below.
Empidinae
. Many Empidinae form mating swarms (see Chvala 1983). The up and down movement of flies within these mating swarms is the basis for the name 'dance flies'. Many Empidinae transfer nuptial gifts from male to female during courtship and mating (Cumming 1994). Depending on the species, these nuptial gifts include prey or various types of inedible objects, in many
Hilarini
('balloon flies') presented in silken balloons secreted from special glands in the swollen basitarsus of male leg I (see Young & Merritt 2003).
The Empidinae are divided into two tribes, the Empidini and Hilarini (see Bickel 1996). The Empidini include many species in the genus
Empis
, and some are large sized and have an elongate proboscis. Some Empidini exhibit sex-role reversed courtship behaviour where females gather in swarms to await males that choose mates. These species exhibit many female secondary sexual characters used in courting males, such as enlarged wings, pinnate leg scales, and eversible abdominal pleural sacs (Cumming 1994).
The Hilarini include two highly speciose and widespread genera,
Hilara
and
Hilarempis
, in which males have swollen basitarsal silk glands, as noted above. Individuals of these two genera are frequently seen skimming back and forth above the surface of streams. For other genera in the Hilarini, see Bickel (1996, 1998, 2002).
Hemerodromiinae
. Members of this subfamily, which includes the genera
Hemerodromia
and
Cladodromia
, have elongate fore coxae and raptorial fore legs (MacDonald 1998).
Clinocerinae
. Included in this subfamily are species of
Asymphyloptera
, which occur on seeps, and seven Australian species of the genus
Clinocera
, found in cascades of Australian streams (Sinclair 2000).
Ceratomerinae
. The genus
Ceratomerus
has a classical Gondwanan distribution of Australia, New Zealand and southern South America. Individuals of this distinctive genus are common on rocks in rainforest streams, and 19 species are known from eastern Australia (Sinclair 2003).