BRACHYCERA, Muscomorpha Schizophora Calyptratae, Oestroidea

Number of British species: 11

Size: M-L

Difficulty: 2

Medium sized to large flies (9-18 mm). Body largely without bristles, nearly bare, or body and legs covered in a soft pilosity, making these insects resemble bees or bumblebees. Mouth opening small, mouthparts rudimentary; antenna small; ptilinal suture usually with the ends converging below the antennal insertions. Lower calypter large. Vein M₁ strongly curving or with an angle in the direction of the wing margin or ending in vein R₄₊₅; in the latter case cell r₄₊₅ petiolate. Subscutellum flat or strongly swollen; meron in some cases with bristles along its hind margin, near the posterior spiracle (often difficult to see because of the dense pilosity).

The larvae are parasites in the nostrils or nasal cavities of mammals, especially sheep and goats but also occasionally antelopes, deer, camels and horses. The host relation is rather specific. Oestridae are larviparous which means that larvae (instead of eggs) are deposited into the nostrils of the host, usually from a distance. The female hovers just in front of the host and ejects the larvae into the host's nostrils. The larvae migrate to the nasal cavities and, in most cases, later into the pharynx. Fullgrown larvae leave their host through the nostrils or mouth opening and pupate in the soil. The adults have reduced mouthparts and do not feed. They seem to be rather inactive insects and are relatively rarely observed. A conspicuous phenomenon in this family is hilltopping, i.e., the habit of the adults seeking out high places or landmarks, in order to raise the chances of males and females meeting each other.

Emden (1954), Zumpt (1965)