What Bug Is That? The guide to Australian insect families.

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Therevidae

Overview

A cosmopolitan family, containing fewer than 1,000 described species worldwide, with flies of moderate to small size, often with patterned wings and silvery pruinescent markings on the body. Australia has the one of the world's least known therevid fauna with only 40% of the nearly 700 recognised species described. Several important monographs were published in the early 20th Century (White 1915; Mann 1928, 1929, 1933). A large number of descriptive studies have been published since Irwin and Lyneborg (1989) last catalogued this region, with the majority completed in the last decade (Winterton & Irwin 1999; Winterton et al. 1999a,b; Winterton 2000; Winterton et al. 2000; Lyneborg 2001; Winterton & Irwin 2001; Winterton et al. 2001; Hill & Winterton 2004). Field work regularly continues to uncover specimens not yet represented in collections so our estimate of numbers of undescribed species is still increasing.

In Australia there are three major groups, with one currently recognised endemic subfamily, the Agapophytinae (Winterton et al. 2001) distinguished by the velutum patches on fore and hind femora and ventral surface of gonocoxites, no antero-ventral seta subapically on hind femur, and usually wing cell m3 closed. The cosmopolitan Therevinae are represented by the Anabarhynchus genus-group; often stout flies that have no velutum patches on femora or gonocoxites, usually have a small number of long hair-like adpressed setae below the posterior thoracic spiracle, and hind femora often with simple erect setae and dorsally adpressed, whitish, semi-scaly setae. The placement of the Taenogera genus-group (Winterton et al. 1999a) remains a challenge. The Taenogera genus-group are usually fine-bodied flies with an open wing cell m3, no velutum patches on fore and hind femora or ventral surface of gonocoxites, and usually a single antero-ventral seta subapically on hind femur.

The family Apsilocephalidae is very closely related to Therevidae, and will key to this family. Three species are described from Australia, they are found in eastern Tasmania and are all uncommon in collections. They can be distinguished from Therevidae by their highly modified male genitalia, with a coiled phallic complex.

Adults frequent a wide variety of habitats, often in rather dry situations. Anabarhynchus are often found on sand dunes or beaches, Agapophytus is common on tree trunks, and Ectinorhynchus can often be seen hovering in small swarms above and among shrubs. Little is known of the adult habits; some genera are found at flowers, and many track drying creek beds. Adults are often collected in very large numbers in Malaise traps placed across flight paths in gullies (Lambkin et al. 2002). The larvae are smooth and vermiform, with a rather well-developed head; the abdomen is secondarily divided into some 16 apparent segments, and terminates in a pair of tiny pseudopods (Colless & McAlpine 1991). They are found mainly in sand or soil close to the surface, are predacious, and are occasionally reported to give a painful bite (English 1950). The prepupal larva lies in the soil in a characteristically curved attitude.

Description

Many species show marked sexual dimorphism. Some resemble small Asilidae, others Rhagionidae or Apioceridae, while many are wasp mimics. The antennae are sometimes very distinctive, often with a greatly elongate scape in Agapophytus , and a thickened scape in Neodialineura .

Distribution

Australia has the world's richest therevid fauna and the genera show an extraordinary degree of endemism. Of the 24 described genera, 22 are found only in this region. Anabarhynchus , one of Australia's commonest genera, is also dominant in New Zealand, and close relatives are found in South America. Ectinorhynchus is also recorded from New Zealand, and close relatives are found in New Caledonia and Chile. Species of Therevidae are generally most abundant in our semi-arid and arid open forests, they are uncommonly encountered in rainforest habitats. Alpha-diversity can be quite high, for example the Warrumbungle Mountains area is home to more than 100 species. Australia's aridity is geologically recent (beginning 25 mya) and many of its therevid species belong to morphologically similar species-swarms that may have radiated in this period, such as Anabarhynchus and Acraspisa ; however, there are also ancient, clearly Gondwanan, links with Chilean taxa, such as Melanothereva, Pachyrrhiza and Entesia .

  • Therevidae

  • Anabarhynchus sp.

  • Anabarhynchus sp.

  • Therevidae

  • Therevidae, female

  • Therevidae, male

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