Key to males of Callomyia species in North America

1. Abdomen with yellow or brownish-yellow markings; if silver-blue markings present, restricted to tergite 5............... 2

- Abdomen dark brown to black, without yellow or brownish-yellow markings; silver-grey, silver bluish-grey, silver-blue or metallic bluish-white markings usually present.............................................................. 4

2. Yellow markings on abdomen more brownish-yellow (Figs 9, 19); tergite 5 without silver-blue markings; hind tarsomere 1 long and narrow, slightly narrower than apical width of hind tibia; hypandrial process with long finger-like basoventral lobe (Fig. 59).................................................................................. C. calla Kessel

- Yellow markings on abdomen yellow to bright yellow (Figs 7, 14, 8, 24); tergite 5 usually with lateral to anterolateral silverblue markings (Figs 7, 14); hind tarsomere 1 thicker, subequal to or slightly broader than apical width of hind tibia; hypandrial process with shorter basoventral lobe (Figs 58, 64)........................................................... 3

3. Lemon yellow markings on abdominal tergites 1–4 (Figs 7, 18); sternite 8 yellow; hind tarsomere 1 length approximately 2X width, slightly broader than apical width of hind tibia; molar-like surstylus in posterior view with ventral inner cusp broadly truncate medially (Fig. 66)........................................................ C. browni Cumming sp. nov.

- Yellow markings only on abdominal tergites 1–3 (Figs 14, 24), sometimes only on tergites 1–2; sternite 8 brown to grey; hind tarsomere 1 length approximately 2.5X width, subequal to apical width of hind tibia; molar-like surstylus in posterior view with ventral inner cusp more narrowly truncate medially (Fig. 69).................................. C. venusta Snow

4. Thorax partially dark brown to black with distinct metallic bluish-white or silver-blue markings on lateral portion of presutural scutum and most of postsutural scutum (Figs 5, 8, 16, 17); abdominal markings more blue, either metallic bluish-white or silver-blue (Figs 5, 6, 8).................................................................................. 5

- Thorax mainly dark brown to black, sometimes with silver-grey dusting on scutum (Figs 15, 20–23); abdominal markings more silvery, either silver-grey or silver bluish-grey (Figs 4, 10–13) (indistinct in some specimens)..................... 6

5. Metallic bluish-white markings on abdominal tergites 1–4 and 6 (Figs 5, 6); legs mainly brown (Fig. 5); halter dark brown; surstylus broadly lamellate with narrow ventral process, hypandrial process trifid (Fig. 56)...... C. arnaudi Cumming sp. nov.

- Silver-blue markings only on abdominal tergites 1–4 (Fig. 8); legs mainly pale yellow with hind leg darker (Figs 8, 17); halter yellowish-orange; surstylus bifid with long outer and inner processes, hypandrial process bifid (Fig. 57)..... C. bertae Kessel

6. Abdomen primarily dark brown to black with silver-grey markings (when present) restricted to tergites 1 and 2 or tergites 3 and 4 (Figs 12, 13)..................................................................................... 7

- Abdomen partially dark brown to black with more extensive silver-grey or silver bluish-grey markings on at least tergites 1–5 (Figs 4, 10, 11)........................................................................................ 8

7. Mid tibia with median anterodorsal seta usually present above median dorsal seta (Fig. 49); abdomen usually with posterolateral to posteroventral silver-grey markings on tergites 3 and 4 (Fig. 12); surstylus bifid with long outer and inner processes, hypandrial process bifid (Fig. 62)......................................................... C. proxima Johnson

- Mid tibia with median anterodorsal seta absent, only median dorsal seta present (Fig. 50); abdomen with lateral silver-grey dusting on tergites 1 and 2 (rarely absent), sometimes extending to tergites 3 and 4 (Fig. 13); surstylus molar-like, hypandrial process trifid (Fig. 63)................................................................... C. velutina Johnson

8. Wing clear (Fig. 47); base of hind femur with strong stout posteroventral seta (Fig. 53); surstylus molar-like (Fig. 55)................................................................................... C. argentea Cumming sp. nov.

- Wing yellowish-brown tinted (Fig. 48); base of hind femur with long thin posteroventral seta (Fig. 54); surstylus broadly lamellate with narrow ventral process (Figs 60, 61)........................................................... 9

9. Halter brown to dark brown; silver markings on abdomen silver-grey (Fig. 11); antenna with first flagellomere elongate-conical (Fig. 42); scutum with 7–8 notopleural setae; mid tibia with median anterodorsal seta absent, only median dorsal seta present (see Fig. 50); hypandrial process trifid, with 2 apical projections and 1 basoventral lobe (Fig. 61); epandrial apical process elongate and pointed (Fig. 61); epandrial ventral lobe short and broad (Fig. 61)................... C. gilloglyorum Kessel

- Halter orange; silver markings on abdomen more silver bluish-grey (Fig. 10); antenna with first flagellomere short-oval (see Fig. 41); scutum with 6 notopleural setae; mid tibia with median anterodorsal seta usually present above median dorsal seta (see Fig. 49); hypandrial process simple, without projections (Fig. 60); epandrial apical process short and broad (Fig. 60); epandrial ventral lobe long and narrow, curved posteriorly (Fig. 60)................................ C. corvina Kessel