Aridefferia arida (Williston)

Erax aridus Williston, 1893: 254 .

Recognition characters: Grayish black species; length 16–26 mm; mystax white with black bristles below and on sides; mesonotum black, setae black, anteriorly on postpronotal lobe (humeri of authors) and laterally, above wings white; bristles white; scutellar setae, long black, in female few white basally, 18–24 marginal bristles; wings hyaline, veins brown; abdominal segments of male 1–5 thinly brownish pollinose, apex of 5 grayish, 6–7 white pollinose; female sides of 1–7 and posterior margins 2–6 grayish pollinose; genitalia black; legs black.

Distribution: TETON: Teton Park, 9 Aug. 1949 (GD-USU).

Habitat: Sagebrush steppe shrub and grassland vegetation type.

Ethology: Nothing known.

Prey: None known.