The family contains about 1,600 described species worldwide, most diverse in arid and semiarid regions with sandy soils.

[1] Adult Therevidae are small- to medium-sized with a body length of 2.4 to 18 mm and a hairy integument.

The coloration ranges from shades of yellow to black, but commonly the background colour is masked by the tomentum.

The scape and pedicel are pubescent; In contrast to the related and confusingly similar family Asilidae, the labium in the Therevidae is not a piercing, predatory organ, but ends in two fleshy labella adapted to the sucking of liquid foods.

The abdomen is tapered and elongated, typically 3 to 4 times as long as its broadest width when not extended for activities such as oviposition.

The wing venation is relatively complex but without a particular conformation to distinguish the Therevidae from other families of Asiloidea.

This has an elongated shape and terminates at the apex with three angles from which the first three branches of media spring.

The fourth branch, M 4 (or CuA 1 according to a different interpretation), originates from the apex of the posterior basal discal cell.

The cubit and anal converge on a short common branch before reaching the apex.

The larva is apodous and eucephalic, cylindrical, very long and thin, and with tapered ends.

The postembryonic development in known forms, five instars and pupation takes place in the spring.

Larvae also are located in other substrates such as decomposing organic matter and under the bark of trees.

The observation of the behaviour of known forms highlights voracious feeding and agile movements.

When exposed to light, the larvae of the Therevidae dig back into the substrate with rapid movements.

Although inhabiting semiarid regions, or possibly for that very reason, since that is where prey for their larvae are likely to be plentiful, adults are particularly attracted to water, generally remaining near pools or other sources of moisture.

Revision of the higher taxa, based on the phylogenetic cladistic relationships between various groups of Asiloidea has led to a better understanding of their ranks and interrelationships.

Asilidae Bombyliidae Clade showing relationship of Asiloidea At present, over 1, 600 species are known.

After taxonomic revisions by Lyneborg (1976) and Winterston et al. (2001), the family is divided into four subfamilies, among which the most representative in size and diffusion is the Therevinae: In addition to the 121 living genera are several extinct genera known from Cenozoic deposits including Dasystethos, Glaesorthactia, Kroeberiella, and Palaeopherocera, in doubt is Helicorhaphe.

[citation needed] The oldest known member of the family is Cretothereva from the Early Cretaceous (Aptian) Crato Formation of Brazil.

[3] The habitat of the Therevidae is more varied than that of other Asiloidea, but as in Asiloidea, preferred ecosystems better suit the larvae, so these insects are more common in thickets of xerophilous plants (garrigue and maquis, in deserts and on sandy beaches.

The Therevinae are present in all continents,[citation needed] with a lower frequency in the eastern region .

A revision of the North American two-winged flies of the family Therevidae.

Cole, F.R., 1960 Stiletto-flies of the genus Furcifera Kröber (Diptera: Therevidae).

Phylogeny, classification, and biogeography of the cycloteline Therevinae (Insecta: Diptera: Therevidae).

Brasilian Therevidae (Diptera): a checklist and descriptions (sic) of species.

A revision of the Therevine stiletto-flies (Diptera: Therevidae) of the Ethiopian Region.

of Entomology [eds] Diptera of Patagonia and South Chile, based mainly on material in the British Museum (Natural History).