http://www.collembola.org/key/hypoidae.htm - Last updated on 2020.11.30 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

The rationale for taxa used and not used as well as subtaxonomic classification for some taxa is to be provided.

Key

Note that no distinction between subtaxa and taxa is made in the 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