Overview
This family is often called Drosophilid-flies, Ferment-flies or Vinegar-flies.
The biology for most species is unknown, as many are represented in collections by a handful of specimens taken at random over large areas. Species associated with rotting fruit (and therefore easily lured to baits) and those found on deliquescing fungus are well represented in collections. About 40% of the Australian drosophilid fauna-most species of
Mycodrosophila
and
Hirtodrosophila
and some species of
Scaptodrosophila
-can be found on or near fungus, but only about 20% of species are attracted to decaying fruit; these facts highlight the inappropriateness of the name 'fruit flies' for the entire family. Rotting (especially fermenting) fruit in kitchens, gardens and forests will lure these flies, primarily species of
Drosophila
, but also of
Scaptodrosophila
. Most species of the former and few of the latter genus are easily cultured in the lab and, as a consequence, are useful for genetic studies.
It is important to note that the degree to which complexes of cryptic species have been identified among the hundreds in the
Drosophila melanogaster
species group is more a reflection of the depth to which they have been studied in vitro than evidence for a unique evolutionary phenomenon within the family or order. (By contrast, the extraordinary morphological diversification and speciation of hundreds of species in Hawaii is indeed a unique phenomenon within the family). Were other genera amenable to such intensive experimentation and analysis as
Drosophila
, they too would probably also yield complexes of related species. Taxonomic decisions within the genus
Drosophila
, however, continue to rest substantially on identification of differences in the morphology of male terminalia.
Description
Drosophilids are unlike other acalyptrate flies because they have a proclinate, and usually two reclinate, orbital bristles and a bare anepisternum (
Mycodrosophila heterothrix
McEvey & Bock has exceptional anepisternal setulation). Two Australian species lack proclinate orbitals:
Liodrosophila macera
Bock has only one large reclinate and
Scaptodrosophila aclinata
McEvey & Barker has three small reclinates. Drosophilid species with a non-plumose arista are rare in Australia so most workers will jump to that part of a generic key that separates the five largest genera (all with plumose aristae):
Scaptodrosophila
(30% of the fauna),
Drosophila
(13%),
Hirtodrosophila
(11%),
Leucophenga
(9%) and
Mycodrosophila
(9%). Species of
Scaptodrosophila
are characterised by having one, two or all three of the following attributes: three subequal katepisternal bristles, a single vibrissa, and a proepisternal setula;
Hirtodrosophila
and
Drosophila
differ by having unequal katepisternal bristle and no pro-episternal,
Drosophila
species have the second oral seta at least half the length of the vibrissa (Bock 1982). Drosophilid wings are hyaline, infuscate or patterned. In species of
Stegana
and
Eostegana
wings are bent elytra-like over the abdomen when resting. The subcostal break (second incision of vein C) is sometimes deep and formed into a protruding blackened lappet in
Mycodrosophila
sensu stricto,
Paramycodrosophila
,
Styloptera
,
Dettopsomyia
and
Hirtodrosophila lappetata
McEvey & Bock.
Distribution
Geneticists apply the name 'fruit fly' to
Drosophila (Sophophora) melanogaster
, although this is apt for some drosophilids as the name leads to confusion with the 'true' fruit flies-Tephritidae. Unlike tephritids the drosophilids are not known to impact negatively in any area of commerce, nor are they known to be vectors of disease in Australia. They are not known to initiate rot in unspoiled fruit, but are frequently incorrectly regarded as harmful. In error, many a fruit-gardener has invented a device that accumulates and drowns huge numbers of drosophilids as a control against 'fruit fly' (tephritids)!
Drosophila (S.) flavohirta
, an endemic species that breeds in myrtaceous blossom has spread from Australia to South Africa and Madagascar (McEvey et al. 1989), where its presence diminishes honey yield from
Eucalyptus
. Another flower-dwelling species,
Scaptodrosophila hibisci
, and a close congener,
S. aclinata
, spend most of their lives within native Hibiscus flowers and have distributions extending into drier parts of Australia (McEvey & Barker 2001).
The greatest concentration of drosophilids occurs, however, in more humid and shaded forest habitats. Species diversity is highest in north-eastern Australia where it appears to be the product of an overflow of the extremely rich New Guinean fauna. Further south in Australia a second centre of species diversity (in the McPherson botanical region) has a high degree of endemism: of the 108 species reported in north-eastern New South Wales only 42 occur also in rainforests around Cairns (McEvey 1994). About 20 cosmopolitan species are associated with the activities of humans and occur in or near buildings (often in kitchens), especially where ferment-odours accumulate in still air around fruit, vegetable scraps, and wine or beer. In arid parts of Australia, Drosophilidae are difficult to find or rare; for these regions, the family is represented in collections by a small assortment of species, most frequently
Scaptomyza
and
Leucophenga
species.
The family has 70 genera worldwide, and is represented in Australia by 35 of these; five genera
Balara
,
Bialba
,
Collessia
,
Crincosia
and
Poliocephala
are endemic and four are monotypic, but this may change as further material is examined from New Guinea. There are 290 Australian species, with about 40 known but undescribed. In recent years new taxa have emerged by fruit-baiting at different elevations in sclerophyll forests and from Malaise and light traps set across a range of habitats. That part of the fauna (e.g.
Acletoxenus
,
Amiota
,
Cacoxenus
,
Gitona
spp.) associated with insect exudates, animal excreta, sap fluxes, and fermenting nectaries have been very poorly sampled. Worldwide there are scattered records of drosophilid larvae preying on-or feeding near-aphids, mealy bugs, white fly, spider eggs, terrestrial crabs, partially submerged simuliid larvae and bee larvae.