Key to the males of Xenochironomus

[The species X. lacertus, X. flaviventris and X. longicrus were not included in the key because there are no diagnostic characters in their original descriptions.]

1. Setae of anal tergite distributed in one area................................................................. 2

- Setae of anal tergite distributed in two areas................................................................. 6

2. Inferior volsella with plumose setae....................................................................... 3

- Inferior volsella with simple setae........................................................................ 5

3. Sternite VI with large dark setae.......................................................................... 4

- Sternite VI without large dark setae........................................... Xenochironomus xenolabis (Kieffer)

4. Sternite VI with 14 setae. Superior volsella with microtrichia only in the inner region.................................................................................................. Xenochironomus trochanteratus (Thompson)

- Sternite VI with 4 setae. Superior volsella completely covered by microtrichia............ Xenochironomus tuberosus Wang

5. Superior volsella exposed (visible)............................................ Xenochironomus amazonensis sp. n.

- Superior volsella unexposed (located inside tergite IX)........................ Xenochironomus ugandae (Goetghebuer)

6. Setae in the latero-posterior region of tergite IX present............................... Xenochironomus alaidae sp. n.

- Setae in the latero-posterior region of tergite IX absent........................................................ 7

7. Anal point long; apex of the anal point surpassing or just reaching the inferior volsella...... Xenochironomus mendesi sp. n.

- Anal point short; apex of the anal point not surpassing or reaching the inferior volsella............................... 8

8. Inferior volsella wide; superior volsella long and curved ventrally.................... Xenochironomus ethiopensis sp. n.

- Inferior volsella narrow; superior volsella short and straight.................................................... 9

9. Superior volsella fingerlike; inferior volsella with 2–3 setae at the apex............... Xenochironomus trisetosus (Kieffer)

- Superior volsella pediform; inferior volsella with>3 setae at the apex........................................... 10

10. Gonocoxite with setae as long as the gonostylus; gonostyus rounded........................ Xenochironomus grini sp. n.

- Gonocoxite with setae shorter than the gonostylus; gonostylus narrow apically................................... 11

11. Apex of the inferior volsella rounded............................................................................................. Xenochironomus ceciliae Roque et Trivinho-Strixino, Xenochironomus canterburyensis (Freeman)

- Apex of the inferior volsella spatulate............................................. Xenochironomus martini sp. n.