Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

FNZ 24 - Therevidae (Insecta: Diptera) - Popular summary

Lyneborg, L 1992. Therevidae (Insecta: Diptera). Fauna of New Zealand 24, 140 pages.
( ISSN 0111-5383 (print), ; no. 24. ISBN 0-477-02632-X (print) ). Published 04 Mar 1992

Popular summary

Therevidae or stiletto-flies are distributed worldwide, with some hundreds of species in each major zoogeographical region. The Australian/Oceanian region is probably the richest in Therevidae, with an estimated 600 species. Less than one-fourth of these have so far been described.

The New Zealand fauna of Therevidae is especially rich in relation to the size of the country, and will probably prove to comprise about 100 species when fully explored. This figure equals that for the entire European fauna. At present 69 species have been described and named, 52 of them for the first time as a result of this revision of the family.

These 69 species are placed in only three genera, of which Anabarhynchus is by far the largest, with 62 species. The endemic new genus Megathereva has been created for three species, and four are placed in Ectinorhynchus, a genus with Australian affinities.

Adult Therevidae are rather generalised flies varying in length from 5 mm to 18 mm, and mostly with the abdominal segments rather conspicuously 'furry'. They can be met with in a great variety of habitats, but are relatively seldom seen. Preferred habitats are coastal scrub and sandy ocean beaches, and also sandy lake shores and river beds; wetter habitats are also exploited.

Adults have been collected from September to April, but most abundantly in the months of summer, November to February.

The slender, worm-like larvae live in sand or loose soil, are very mobile, and are voracious predators on insect larvae and earthworms. They appear to be 20-segmented, because the 8 abdominal segments are each secondarily constricted. In the prepupal stage the body assumes a U-shaped curvature. The pupal stage lasts for only a week or two, and is especially vulnerable to desiccation and to attack by predators.

There is a great need for more information on the biology of New Zealand's Therevidae.


Adults are readily captured by sweep-netting, and are also often taken in Malaise traps. They should be preserved for study as dry, pinned specimens; moisture can ruin the fine pattern of minute hairs on the body, which may be helpful in identification. Larvae and pupae can be collected by vigorously sifting the top 5-8 cm of substrate in a 20-mesh sieve. Larger larvae and pupae are retained in the sieve, and smaller larvae will appear on top of the sifted soil. Larvae may be cannibalistic, and should be kept in individual tubes.