Key to European species of Ptilomyia Coquillett.

1 wing hyaline, dm-cu not dark infuscated; costal index I = 0.9-1.0; frons obviously blueish grey; abdomen densely grey dusted; ♂ terminalia as Fig. 3: epandrium small and broadly divided before cercus (Fig. 3: dep); surstylus complex (Fig. 3: su) with large cube-shaped lateral evagination and distinct anteriorly directed medial spine; hypandrium H-shaped (Fig. 3: hy); tip of phallus ending in one slightly sclerotised spine (Fig. 3: sph)............................ shoka Mathis & Zatwarnicki

- wing slightly brownish, dm-cu distinctly brownish infuscated; costal index I may be <0.9; frons and face brown to blue-grey; abdomen dusted to subshining; ♂ terminalia otherwise........................................................ 2

2 4 rows of acrostichal setae; costal index I <0.85; ♂ tergite 5 subshining and distinctly longer than tergite 4; ♂ terminalia as Fig. 1: epandrium broad and not divided before cercus, with distinct ventrally directed lateral keels (in dorsal view visible as dark stripes, Fig. 1: vkep); surstylus (Fig. 1: su) medially directed, with submedial teeth; hypandrium more X-shaped (Fig. 1: hy); tip of phallus ending in three sclerotised spines (Fig. 1: ph)................................... angustigenis (Becker)

- 6 rows of acrostichal setae; costal index I> 0.9; ♂ tergite 5 dusted and only slightly longer than tergite 4; ♂ terminalia as Fig. 2: epandrium narrow and divided before cerci (Fig. 2: dep), without keels; surstylus posteriorly directed, simple shaped with straight edges (Fig. 2: su); hypandrium U-shaped (Fig. 2: hy); tip of phallus simple, without any sclerotisation or spines (Fig. 2: ph)................................................................................. kairensis (Becker)