Suborder Brachycera

Five or fewer (usually 3) antennal segments, the 3rd sometimes annulated (subdivided by rings), sometimes with a terminal style (illus., p. 275), only rarely with an arista (see opp.). Rs usually 3-branched (6.4+5 forked). No frontal suture. Anal cell generally longer than 2nd basal cell, and in most cases closed near wing margin. Mostly medium-sized to large, relatively robust flies.

The families in this suborder may be divided into 3 groups on the basis of form of 3rd antennal segment and number of pads on last tarsal segment:

1. 3rd antennal segment annulated or subdivided; tarsi with 3 pads: Xylophagidae, Xylomyidae, Stratiomyidae, Taban-idae, and Pelecorhynchidae.

2. 3rd antennal segment not annulated; tarsi with 3 pads: Rhagionidae, Nemestrinidae, and Acroceridae.

3. 3rd antennal segment not annulated; tarsi with 2 pads or none: the remaining families (Hilarimorphidae through Dolichopodidae).

XYLOPHAGID FLIES Family Xylophagidae

Identification: Third antennal segment elongate. M3 cell open (except in Rachicerus, in which the antennae appear many-segmented). Calypters (illus., p. 275) small or vestigial. At least middle tibiae with apical spurs.

Xylophagids are not common; the ones most often seen are in the genera Xylophagus and Coenomyia. Xylophagus flies are slender and ichneumonlike, generally 10-13 mm., with eyes bare, the scutellum lacking spinelike protuberances, and the posterior cells usually longer than wide. Coenomyia flies are robust, 14-25 mm., with eyes pubescent, the scutellum bearing 2 spinelike protuberances and the posterior cells about as long as wide. Other xylophagids are 2-9 mm. and rare. Larvae occur in decaying wood or in the soil.

XYLOMYID FLIES Family Xylomyidae

Identification: Similar to Xylophagidae (most resemble Xylophagus), but with the M3 cell closed.

These flies are not very common, but those most likely to be encountered are slender, ichneumonlike, and 10 mm. or less. Larvae occur in decaying wood or under bark.

SOLDIER FLIES Family Stratiomyidae

Identification: Third antennal segment rounded or elongate. Branches of R crowded toward anterior part of wing, with R5 ending in front of wing tip.

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