http://www.collembola.org/key/hypoidae.htm - Last updated on 2024.10.31 by Frans Janssens

Checklist of the Collembola: Key to the genera of Hypogastruridae

This key is still under construction. Note that missing figures will be provided as soon as possible. Currently, the key is in the feasibility study phase to find out how to integrate in the checklist in a modular way a key that has been generated with DELTA.

Rationale

Key

1(0). Head with 8 + 8 eyes........................................ 2 Head with fewer than 8 + 8 eyes............................ 18
2(1). Apical organ of third antennal segment with 2 or no papillae.. ......................................................... 3 Apical organ of third antennal segment with 5 papillae (fig.1)............................................. Biscoia
Fig.1.
3(2). Anal spines absent (fig.2a)................................. 4 Anal spines present, at least small (fig.2b)................ 5
Fig.2.
4(3). First thoracic segment with 1 + 1 setae........ Ecuadogastrura First thoracic segment with 3 + 3 setae.......... Choreutinula
5(3). Anal spines 2 or 3.......................................... 6 Anal spines 8 (fig.3).......................... Octoacanthella
Fig.3.
6(5). Furcula absent................................... Knowltonella Furcula present............................................. 7
7(6). Mandible with 1 or no apical teeth or reduced teeth facing forward (fig.4a&b)........................................ 8 Mandible with 3 or more apical teeth facing inward (fig.4c&d). ......................................................... 9
Fig.4.
8(7). Maxilla complex with ciliate lamella (fig.5a)... Barbagastrura Maxilla without ciliate lamella (fig.5b)........ Stenogastrura
Fig.5.
9(7). Labium with only acuminate or truncate setae............... 10 Labium with trumpet shaped apical setae (fig.6)............... ............................................ Gnathogastrura
Fig.6.
10(9). Anal spines 2 (fig.7b-d)................................... 11 Anal spines 3 (fig.7a).......................... Triacanthella 1
Fig.7.
11(10). Anal spines small or large, arising from separate papillae (fig.7c-d)............................................... 12 Anal spines very small and arising from single papilla (fig.7b)........................................... Franzura
12(11). Unguiculus 1/7th or more as long as inner unguis........... 13 Unguiculus less than 1/9th as long as inner unguis......... 17
13(12). Mucro spoon shaped with lateral lobe or spine (fig.8a-e)... 14 Mucro varied but never spoon shaped (fig.8f-j)............. 15
Fig.8.
14(13). Postantennal organ large with posterior arms usually curved around boss (fig.9a); seta m2 present on thoracic segment 2 (fig.9b)...................................... Mitchellania Postantennal organ posterior arms large, not curved around boss (fig.9c); seta m2 absent on thoracic segment 2 (fig.9d).................................... Ceratophysella
Fig.9.
15(13). Postantennal organ absent........................ Celegastrura Postantennal organ present................................. 16
16(15). Maxilla with lamella 4 hooked, strong and reaching beyond tip of lamella 50 (fig.10b)........................ Hypogastrura Maxilla with lamella 4 rounded, shorter than and hidden by lamella 5 (fig.10a)................................ Mucrella 2
Fig.10.
17(12). Postantennal organ with weak lobes (fig.11a&b)..... Schoettella Postantennal organ without lobes (fig.11c)..... Gomphiocephalus
Fig.11.
18(1). Postantennal organ absent.................................. 19 Postantennal organ present (fig.12)........................ 26
Fig.12.
19(18). Apical organ of third antennal segment with 2 or no guard papillae................................................. 20 Apical organ of third antennal segment with 4 or 5 guard papillae (fig.13)................................ Acherongia
Fig.13.
20(19). Eyes 2 + 2 or fewer per side............................... 21 Eyes 4 + 4 - 5 + 5 per side................................ 24
21(20). Eyes 2 + 2...................................... Acheroxenylla Eyes absent................................................ 22
22(21). Furcula & tenaculum often reduced but present (fig.14)..... 23 Furcula absent.................................. Acherontiella
Fig.14.
23(22). Mucro fused to dens (fig.14b) or absent.......... Acherontides Mucro separate from dens (fig.14a).......... Pseudacherontides
24(20). Mandible short without long apex, apical teeth large (fig.15a)........................................... Xenylla Mandible with long thin apex and small apical teeth (fig.15b). ........................................................ 25
Fig.15.
25(24). Fourth antennal segment with 4 heavy blunt setae (fig.16a).... ............................................... Paraxenylla Fourth antennal segment with 5 heavy blunt setae (fig.16b).... ............................................... Thibaudylla
Fig.16.
26(18). Mandible normal (fig.17c).................................. 27 Mandible reduced (fig.17a&b).................... Microgastrura
Fig.17.
27(26). Furcula reduced to single mass, paired rudiments (fig.18b) or absent................................................... 28 Furcula with clear manubrium and dens (fig.18a)............ 31
Fig.18.
28(27). Eyes absent................................................ 29 Eyes present..................................... Parawillemia
29(28). Claw with strong inner teeth (fig.19a)............... Tafallia Claw without inner teeth................................... 30
Fig.19.
30(29). Furcula completely absent............................ Willemia 3 Furcula vestigial (fig.19b).................... Willemgastrura
31(27). Unguis 6 or less times as long as basal width.............. 32 Unguis 8 or more times as long as basal width (fig.20)........ ............................................ Ongulogastrura
Fig.20.
32(31). Anal horns absent.......................................... 33 Anal horns present......................................... 35
33(32). Unguiculus absent.............................. Austrogastrura Unguiculus sometimes reduced (fig.21a&b) but present....... 34
Fig.21.
34(33). Unguiculus large, with clear basal lamella (fig.21c).......... ............................................ Jacutogastrura Unguiculus without basal lamella (fig.21a&b).................. .............................................. Mesogastrura 4
35(32). Base of unguiculus lamellate (fig.21c)..................... 36 Base of unguiculus not lamellate (fig.21a&b)............... 39
36(35). Dens with 6 or fewer dorsal setae.......................... 37 Dens with 7 dorsal setae................................... 38
37(36). Mucro absent or with lamella and/or lateral tooth. Schaefferia Mucro slender tapered, without lamella or tooth. Taurogastrura
38(36). Seta p2 on abdomen 4 larger than p1 (fig.22b).. Typhlogastrura Seta p2 on abdomen 4 smaller than p1 (fig.22a). Bonetogastrura
Fig.22.
39(35). Mucro fused to dens (fig.23a)................. Xenyllogastrura Mucro separate from dens (fig.23b&c)....................... 40
Fig.23.
40(39). Eyes 2 + 2 or fewer.............................. Mesachorutes Eyes 4 + 4 - 6 + 6......................................... 41
41(40). Eyes 4 + 4....................................... Denigastrura Eyes 5 + 5 or 6 + 6............................... Orogastrura

Endnotes

¹ Rare individual specimens of other genera may have 3 anal horns.

² Proxenyllodes will be keyed out here (ecomorphic form). Proxenyllodes is a senior but subjective synonym of Mucrella and is treated here as a nomen dubium.

³ Xenyllogastrura reducta will key out here (see Fjellberg 1991).

⁴ Mesachorutes tiliophilus will key out here. It also shares with this genus the absence of discrete lobes of the PAO which separates other members of Mesachorutes from Mesogastrura.

References