Acrotrichis
Creators: name: Darby, Michael
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Ptiliidae
Acrotrichis

description: Key to the known species of Acrotrichis from Madagascar
Note: dissection of genitalia is an essential prerequisite for most determinations (although it is sometimes possible to see the shape of the spermatheca in specimens in alcohol without the need for dissection).
1. Posterior margin of mesosternal collar strongly sloping at humeri (as Fig. 3 F), larger species (> 0.75 mm)............... 2
- Posterior margin of mesoventral collar barely sloping at humeri (as Fig. 10 G), smaller species (<0.75 mm)............. 25
2. Sides of pronotum and elytra with outstanding setae (note: if there is doubt as to whether these have become abraded, the ante- rior margin of the pygidium without setae)...................................................... A. discoloroides
- Sides of pronotum and elytra without outstanding setae........................................................ 3
3. Mesoventral collar with a median pointed projection (Fig. 6 F).................................................. 4
- Mesoventral collar without a median pointed projection....................................................... 5
4. Smaller species with a more pronounced curve to the pronotal margins (Fig. 31 B)...................... A. superbioides
- Larger, broader species with a less pronounced curve to the pronotal margins (Fig. 6 B)....................... A barclayi
5. Mesoventral collar with a clearly marked median keel (Fig. 7 H)................................................. 6
- Mesoventral collar without a median keel.................................................................. 8
6. Sides of pronotum more rounded (Fig. 35 B), antennomeres 3–8 longer (Fig. 35 C).......................... A. tuberosa
- Sides of pronotum less rounded and antennomeres 3–8 shorter.................................................. 7
7. Keel on mesoventral collar more pronounced (Fig. 7 H), pronotal sides less curved (Fig. 7 B), spermatheca distinctive (Figs. 7 D)........................................................................................... A. bibula
- Keel narrower and less pronounced, pronotal sides more curved (Fig. 24 B), spermatheca distinctive (Fig. 24 D).. A. malitiosa
8. Submentum with 12+ setae.............................................................................. 9
- Submentum with less than 12 setae....................................................................... 13
9. Setae on submentum long (some as long as the mentum) and directed posteriorly (Fig. 12 F), pronotum much broader than the elytra....................................................................................... A. cuspida
- Setae on submentum shorter, width of pronotum not so pronounced............................................. 10
10. Mentum with 8 setae arranged 4.2.2 (Fig. 4 E)....................................................... A. africana
- Mentum with more than 8 setae arranged differently......................................................... 11
11. Smaller (<0.90 mm), reddish brown species, mentum setae arranged 3.4.10 + (Fig. 5 I).................... A. africanoides
- Larger (> 0.9 mm), blackish/dark brown species, mentum setae arranged differently................................ 12
12. Submentum with +/- 13 setae; mentum setae arranged 5.2.4........................................... A. impressa
- Submentum with +/- 18 setae; mentum setae arranged 5.3.5......................................... A. subafricana
13. Hind angles of pronotum rounded, not or barely angled....................................................... 14
- Hind angles of pronotum pointed or clearly angled.......................................................... 15
14. Smaller, very rounded species with a distinctive spermatheca (Fig. 32 D)............................... A. tampoketsae
- Larger, flatter species with short and broad elytra.................................................... A. truncata
15. Elytra distinctly narrowed posteriorly, very large species (+/- 1.22 mm), mentum with a pair of long setae at each of the anterior corners (Fig. 29 G).............................................................................. A. strenua
- Elytra parallel sided or rounded, not narrowed posteriorly, smaller species........................................ 16
16. Sides of pronotum sinuate before the hind angle (often the sinuation is slight).................................... 17
- Sides of pronotum clearly rounded or straight before the hind angles, not sinuate.................................. 20
17. Metaventral posterior margin between metacoxae very short (Fig. 22 F).................................. A. loganovi
- Metaventral posterior margin between metacoxae longer (Fig. 16 J)............................................. 18
18. Sides of pronotum strongly curved before hind angles and only very slightly sinuate (Fig. 23 B); male genitalia distinctive.............................................................................................. A. magnifica
- Pronotal margin moderately curved...................................................................... 19
19. Male ventrites six and seven very distinctive (Figs. 6 F,G)............................................ A. hammondi
- Male ventrite six with a few narrow spines only (Fig. 27 G) and seven without any distinctive features......... A. perexigua
20. Mentum with 13 setae in +/- four rows and sides of pronotum feebly curved (Figs. 9 B,H)..................... A. clareae
- Mentum with fewer setae and more strongly curved pronotal sides.............................................. 21
21. Posterior margin of metaventrum between metacoxae short (Fig. 17 H)..................................... A. heissi
- Posterior margin of metaventrum between metacoxae broader (Fig. 3 G)......................................... 22
22. Large blackish species (<0.95 mm)................................................................ A. absona
- Smaller (> 0.9 mm) black or reddish brown species.......................................................... 23
23. Black very shining species, aedeagus with a pointed tip (Fig. 21 D)......................................... A. lauta
- Reddish brown, less shining species...................................................................... 24
24. Ventrite six of male with long fringe of spines, aedeagus distinctive (Fig. 11 I)............................. A. cursitans
- Ventrite six of male with 10 or less spines................................................................. 25
25. Ventrite six of male with one spine (Fig. 20 G) aedeagus pear shaped (Fig. 20 E)........................... A. lacrimosa
- Ventrite six of male without a single spine................................................................ 26
26. Sides of pronotum evenly rounded to hind angle, not sinuate, yellow species (Fig. 13 B)...................... A. difficilis
- Sides of pronotum sinuate before the hind angle (in most cases the sinuation is slight).............................. 27
27. Larger species (> 0.76 mm)......................................................................... A.hova
- Smaller species (> 0.74 mm)............................................................................ 28
28. Yellowish brown species with very sharply pointed pronotal hind angles (Fig. 8 B)............................ A. boothi
- darker species, hind angles of pronotum less pointed (Fig. 24 D)................................................ 29
29. Very small paler species (0.53 mm). The sinuation in the pronotal sides barely detectable.................... A. terminalis
- larger darker species> 0.58 mm ......................................................................... 30
30. The six small species in this category: colini, exigua, minuscula, obscura, and perfida are very difficult to separate on external criteria particularly when specimens are teneral and are best determined by examination of the genitalia, see Figs in the species descriptions.
description: Published as part of Darby, Michael, 2014, Studies of Madagascan Ptiliidae (Coleoptera) 3: The genus Acrotrichis including twenty seven new species, pp. 151-201 in Zootaxa 3866 (2) on pages 156-157, DOI: 10.11646/zootaxa.3866.2.1, http://zenodo.org/record/249555