Key to females of Callomyia species in North America

Females of C. argentea, C. bertae and C. browni are unknown and thus are not included here.

1. Antenna with first flagellomere subtriangular (Fig. 44); abdomen with alternate black and silver-grey markings (Fig. 37)...................................................................................... C. gilloglyorum Kessel

- Antenna with first flagellomere short-oval (Fig. 43); abdomen with yellow, pale orange, metallic bluish-white and/or silverblue markings (Figs 33, 35, 36, 38–40)..................................................................... 2

2. Abdomen entirely yellow (sometimes more brownish-yellow or brownish-orange) (Figs 27, 35)............ C. calla Kessel

- Abdomen darker, never entirely one colour, with yellow, pale orange, metallic bluish-white and/or silver-blue markings (Figs 33, 36, 38–40)........................................................................................ 3

3. Thorax mainly silver-blue dusted with black median dorsal stripe on scutum (Figs 28, 36)............... C. corvina Kessel

- Thorax mainly brown to black with metallic bluish-white or silver-blue markings on lateral portion of presutural scutum, notopleuron and most of postsutural scutum (Figs 25, 30–32, 33, 38–40).......................................... 4

4. Abdominal tergites 1 and 2 pale orange with silver-white dusting, tergite 6 metallic bluish-white (Fig. 33); halter pale orange; legs mainly brown (Fig. 25)..................................................... C. arnaudi Cumming sp. nov.

- Abdominal tergites 1, 2 and sometimes 3 yellow, tergite 5 or 6 silver-blue (Figs 38–40); halter yellow; legs mainly yellow to yellowish-brown with hind leg darker (Figs 30–32)........................................................... 5

5. Abdomen with only tergites 1 and 2 yellow (both interrupted by median dorsal dark band) (Fig. 38); tergite 5 black and tergite 6 silver-blue; mid tibia with long median dorsal seta (Fig. 51)................................... C. proxima Johnson

- Abdomen with tergites 1–3 entirely yellow (Figs 39, 40); tergite 5 silver-blue and tergite 6 black; mid tibia with median dorsal

seta short (Fig. 52) or absent............................................................................. 6 6. Abdomen with silver-blue on tergite 5 interrupted by median dorsal dark band (Fig. 39) (sometimes partially interrupted); scutum with 2–3 presutural intra-alar setae, 3 at least on one side (Fig. 45); mid tibia usually with short median dorsal seta (Fig. 52).................................................................................. C. velutina Johnson

- Abdomen with tergite 5 entirely silver-blue (Fig. 40); scutum with only 2 presutural intra-alar setae (Fig. 46); mid tibia with median dorsal seta absent.................................................................. C. venusta Snow