species have the thorax black dorsally and yellowish laterally. Larvae occur in decaying wood. These flies are not very common.

TRIXOSCELIDID FLIES Family Trixoscelididae

Identification: Sc usually complete. Oral vibrissae present. 2nd basal and discal cells separated. Postvertical bristles converge. Tibiae with preapical bristles. Costa spiny. Orbital plates long, extending nearly to antennae.

Trixoscelidids are very small flies, generally 2-3 mm., most of which occur in the West; only 2 rather rare species occur in the East, 1 in Florida and 1 in Maryland. Some species occur in grassy areas and woodlands; others, including many western species, live in desert areas. Larvae of 1 eastern species inhabit bird nests.

HELEOMYZID FLIES Family Heleomyzidae

Identification: Similar in general appearance to Sciomyzidae (p. 290), but antennae smaller and not projecting forward, oral vibrissae present, and postvertical bristles converging. Costa usually spiny. Orbital plates short, not reaching antennae.

Heleomyzids are fairly common flies usually found in areas of abundant vegetation. Most are brownish and some have spots on the wings. Larvae occur in fungi, bird nests, mammal burrows, and in other places where there are decaying materials.

CHYROMYID FLIES Family Chyromyidae Not illus.

Identification: Small yellow flies with golden eyes. Sc complete. Oral vibrissae weakly developed. 2nd basal and discal cells separated. Tibiae without preapical bristles. Postvertical bristles converge.

Adults of this small but widely distributed group usually occur on vegetation. Larvae probably are scavengers.

SMALL DUNG FLIES Family Sphaeroceridae

Identification: Very small and blackish or brownish. Sc incomplete. Basal segment of hind tarsi somewhat swollen and shorter than 2nd segment.

Sphaerocerids usually occur near manure or other refuse, and are very common. Larvae live in dung and various decaying materials.

ASTEIID FLIES Family Asteiidae

Identification: Mostly 2 mm. or less, and usually light-colored. Sc incomplete. R2+3 ends in costa just beyond end of R\. Post-vertical bristles diverge.

The group is a small one, its members relatively rare. Immature stages are unknown.

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