Key to the genera of Japanese Scathophagidae (males and females)

1. Fore femur and tibia ventrally with remarkable rows of spine-like setae, longer than diameter of femur and tibia (Hironaga & Suwa 2005)........................................................................ Norellisoma Wahlgren

- Fore femur and tibia without ventral rows of long spine-like setae............................................... 2

2. Palpus short and small, less than length of proboscis (Hering 1955)............................. Parallelomma Becker

- Palpus long and large, longer than length of proboscis........................................................ 3

3. Palpus with strong subapical setae about as long as or longer than palpus (see Iwasa (2020, fig. 7))....... Cordilura Fallén

- Palpus without very strong subapical setae (Fig. 2)........................................................... 4

4. Katepisternum with two or three setae..................................................................... 5

- Katepisternum with one seta (Fig. 44)..................................................................... 6

5. Katepisternum with two setae........................................................... Chaetosa Coquillett

- Katepisternum with three setae (Fig. 16)................................................... Cleigastra Macquart

6. Fore tibia ventrally without rows of long spine-like setae but with 1 or more rows of short black spines (Fig. 45).......... 7

- Fore tibia ventrally without rows of both long spine-like setae and short black spines................................ 8

7. Apex of fore tibia with a stout ventral seta (Suwa 1986)..................................... Acanthocnema Becker

- Apex of fore tibia without stout ventral seta............................................... Microprosopa Becker

8. Anepisternum, katepisternum, and anepimeron wholly covered with dense, long erect fine hairs....................... 9

- Anepisternum, katepisternum, and anepimeron covered with sparse fine hairs or bare.............................. 10

9. Palpus distinctly spatulate (Fig. 54)....................................................... Spaziphora Rondani

- Palpus filiform or clavate.............................................................. Scathophaga Meigen

10. Arista plumose (Fig. 30) or short-haired (Figs 34, 40); body shiny yellow........................................ 11

- Arista bare (Fig. 53) or pubescent (Fig. 7); body shiny black, grey microtrichose or dusted.......................... 12

11. Scutellum with pair of strong setae (Fig. 28).............................................. Megaphthalma Becker

- Scutellum with two pairs of strong setae............................................ Megaphthalmoides Ringdahl

12. Arista relatively short, thick and slightly longer than postpedicel; postpedicel enlarged in males (Fig. 2)..................................................................................................... Acerocnema Becker

- Arista rather thin, and distinctly longer than postpedicel; postpedicel not more enlarged in both sex (Fig. 22)................................................................................................ Gimnomera Rondani