Gymnochthebius, : Perkins, 1997

Perkins, Philip D., 2005, A revision of the water beetle genus Gymnochthebius Orchymont (Coleoptera: Hydraenidae) for Australia and Papua New Guinea, Zootaxa 1024 (1), pp. 1-161 : 1-161

Key to species of Gymnochthebius of Australia

and Papua New Guinea

1 Elytral lateral margin with arcuate setae which extend outward to form a fringe (e.g., Figs. 3 , 7 , 62, 66); legs generally shorter and stouter, with setae denser and finer....... 2

­ Elytral lateral margin with rather indistinct setae which lie flat on cuticle, not extending outward to form a fringe (e.g., Figs. 17 , 42, 60); legs often longer and more slen­ der, with protibial and mesotibial setae sparser and stouter........................................ 16

2 Elytral discal punctures non­serial (Fig. 62) ....................................... inlineatus n. sp.

­ Elytral discal punctures serial ...................................................................................... 3

3 Pronotum with anterior and posterior foveae on each side of median groove ............. 5

­ Pronotum without posterior foveae; strongly shining species ...................................... 4

4 Pronotum median sulcus deep, highlighted by shining surrounding cuticle; anterior foveae not confluent with respective pit at anterior extreme of lateral depression; explanate margin of elytra very narrow (Fig. 27) ............................ lustrosulcus n. sp.

­ Pronotum median sulcus almost absent, very faint line interrupted in midlength; anterior foveae each confluent with anterior extreme of lateral depression; elytral margin not explanate, side vertical, very smooth and shining (Fig. 25) ............ radiatus n. sp.

5 Hydrofuge pubescence present on more than first two ventrites ................................. 7

­ Hydrofuge pubescence restricted to first two ventrites; very small species (ca. 1.25– 1.40 mm) with dorsal setae thickened basally .............................................................. 6

6 Dorsum densely clothed in decumbent, short squamiform setae; elytral punctures large, transverse, obliterating intervals; elytral margin with very long fringe of arcuate setae (Fig. 66)...................................................................................... squamifer n. sp.

­ Dorsal pubescence much less dense, setae thinner; elytral punctures closely spaced, about equal in width to intervals; elytral marginal fringe shorter (Fig. 64) .................. ............................................................................................................ nanosetus n. sp.

7 Pronotum and elytra dull but without apparent microreticulation, i.e., pruinose; elytral punctures smaller, about 1/4 width of intervals; (Fig. 40) ....................... levis (Deane)

­ Pronotum and elytra shining ........................................................................................ 8

8 Truncate species, length/width ca. 2.10; convex, shining, uniformly dark brown species ( Fig. 7 ) ......................................................................................... truncatus n. sp.

­ More elongate species. ................................................................................................. 9

9 Pronotal anterior and posterior foveae confluent, forming sinuate longitudinal impressed line; elytra transversely and longitudinally very convex (Fig. 29) ............... ............................................................................................................ trilineatus n. sp.

­ Pronotal anterior and posterior foveae separate ......................................................... 10

10 Elytra deeply striate­impressed, subsulcate (Fig. 54) ...................... subsulcatus n. sp.

­ Elytra not subsulcate ................................................................................................... 11

11 Pronotal anterior margin with small apicomedian point; head and pronotum impunctate; elytral punctures large, deep; pronotum transverse, foveae large; Papua New Guinea (Fig. 70) ........................................................................................ papua n. sp.

­ Pronotal anterior margin arcuate, bisinuate or biangulate; combination of other characters not as above .......................................................................................................... 12

12 Pronotal anterior margin arcuate; elytra very convex, summit of posterior declivity at or slightly before midlength; elytra striate­impressed, intervals with sparse, erect setae (Fig. 31) ....................................................................................................... nicki n. sp.

­ Pronotal anterior margin bisinuate or biangulate; elytra less convex, summit of posterior declivity at about posterior 0.6; elytra various .................................................... 13

13 Pronotal anterior margin angulate where lateral depressions meet anterior margin of disc ( Fig. 5 ) .................................................................................... angulonotus n. sp.

­ Pronotal anterior margin bisinuate ............................................................................. 14

14 Elytral punctures on disc without perceptible setae; head and pronotum very brightly shining (Fig. 21) ............................................................................... resplendens n. sp.

­ Elytral punctures on disc each with decumbent seta .................................................. 15

15 Elytral intervals with sparse, erect, moderately long setae, especially developed on sides and over posterior declivity; setal fringes of pronotum and elytra more developed; aedeagus as illustrated ( Fig. 3 ) ...................................................... setosus n. sp.

­ Dorsal setae less developed; dorsal sculpture generally less impressed; aedeagus as illustrated ( Fig. 1 ) ...................................................................... australis (Blackburn)

16 Elytral discal punctures serial .................................................................................... 17

­ Elytral discal punctures non­serial; metasternal glabrous area flat, tabelliform, subrhomboidal, strongly densely punctate; comparatively flat species (Fig. 68) ................ ........................................................................................................... pluvipennis n. sp.

17 Hydrofuge pubescence covering ventrites 1–4 and present laterally and anteriorly on ventrite 5, forming markedly arcuate hair­line; metasternal glabrous area longer than wide; female last tergite with stout spines ................................................................. 18 ­ Hydrofuge pubescence present on not more than ventrites 1–4; female last tergite without spines ............................................................................................................. 19

18 Head black, contrasting with testaceous pronotum and elytra; pronotal disc less coarsely punctate; form less parallel­sided; females with margin of last tergite arcuate (Fig. 50) ................................................................................................ nigriceps n. sp.

­ More darkly colored species of slightly narrower and more parallel­sided form; pronotal disc more coarsely punctate; females with margin of last tergite sharply angulate (Fig. 52)................................................................................................ fontinalis n. sp.

19 Hydrofuge pubescence covering ventrites 1–2, and present basally on ventrite 3 ..... 20

­ Hydrofuge pubescence covering ventrites 1–3 and present basally on ventrite 4....... 22

20 Pronotal impressions strongly microreticulate, reliefs punctate over effacedly microreticulate ground sculpture; dorsum with faint metallic reflections (Fig. 56) ................... ........................................................................................................ minipunctus n. sp.

­ Pronotal reliefs and impressions shining, non­microreticulate .................................. 21

21 Head black, contrasting sharply with testaceous to light brownish pronotum and elytra; body wider, length/width ca. 2.28; Western Australia (Fig. 19) .......... hesperius n. sp.

­ Dorsum dark brown to piceous; body narrower, length/width ca. 2.45; eastern and northern Australia ( Fig. 13 ) ................................................................... clarki (Deane)

22 Pronotal reliefs dull, matte or microreticulate ............................................................ 23

­ Pronotal reliefs shining between punctures; punctation varying from very fine and sparse to coarse and dense .......................................................................................... 25

23 Pronotal lateral depression produced in obtuse point slightly before midlength (Fig. 39) ..................................................................................................... tenebricosus (Deane)

­ Pronotal lateral depressions arcuate on lateral margins .............................................. 24

24 Elytral punctures smaller than intervals, weakly striate­impressed; pronotal reliefs nearly impunctate; metasternal glabrous area shining (Fig. 35) .................................... ............................................................................................. brisbanensis (Blackburn)

­ Elytral punctures larger than intervals, not striate impressed; pronotum distinctly punctate over matte ground sculpture; metasternal glabrous area matte (Fig. 37) ........ ............................................................................................................... fumosus n. sp.

25 Metasternal glabrous area longer than wide; elytral punctures striate­impressed ..... 26

­ Metasternal glabrous area not longer than wide; elytral punctures various ............... 29

26 Elytral striae deeply impressed; intervals raised, 4th and 6th continuing in raised condition to elytral apices; pronotal foveae deep and large.............................................. 27

­ Elytral striae less deeply impressed; 4th and 6th intervals not continuing in raised condition to elytral apices ................................................................................................. 28

27 All elytral intervals uniformly raised (Fig. 42) .............................. benesculptus n. sp.

­ Even­numbered intervals distinctly higher than odd­numbered intervals (Fig. 46) ..... ...................................................................................................................... weiri n. sp.

28 Head black, pronotum, elytra and appendages testaceous or light brown; central Australia (Fig. 44) ....................................................................................... coruscus n. sp.

­ Dorsum brownish, head darker; explanate margin distinctly wider in females than males; far western Australia (Fig. 48) .............................................. sexplanatus n. sp.

29 Pronotal lateral hyaline border anterior extreme at basal 0.3 of lateral depression ( Fig. 9 ) ............................................................................................................... lividus (Deane)

­ Pronotal lateral hyaline border less developed, anterior extreme at base of lateral depression....................................................................................................................30

30 Pronotal anterior and posterior foveae confluent, forming sinuate longitudinal impressed line; elytra transversely very convex; Papua New Guinea (Fig. 33) ............. ............................................................................................................... bacchusi n. sp.

­ Pronotal anterior and posterior foveae separate ......................................................... 31

31 Pronotal reliefs finely sparsely punctate, highly shining; male with large, probe­like apicomedian process of labrum (Fig. 23) ................................................. probus n. sp.

­ Pronotal reliefs more coarsely, densely punctate ....................................................... 32

32 Pronotal lateral depressions with lateral margin bisinuate, that is, emarginate in front of and behind midlength; elytra strongly punctate, not or only very weakly striateimpressed; narrow species with elytra transversely very convex, semicylindrical( Fig.17 ) ....................................................................................................... semicylindrus n. sp.

­ Pronotal lateral depressions with lateral margin not distinctly emarginate in front of midlength, distinctly emarginate behind midlength; elytra not semicylindrical ........ 33

33 Pronotal anterior­posterior foveae confluent; dorsum black or very dark brown; elytra more deeply striate­impressed; southeastern Australia and Tasmania ( Fig. 15 ) ............ .................................................................................................................... wattsi n. sp.

­ Pronotal anterior and posterior foveae not confluent ................................................. 34

34 Pronotal setae very indistinct; pronotal median groove very narrow; elytral intervals wider than serial punctures; metasternal glabrous area oval ( Fig. 11 ).. notalis (Deane)

­ Pronotal setae very distinct; pronotal median groove wider, deeper; metasternal glabrous area rhomboidal ................................................................................................ 35

35 Dorsum more strongly punctate; margins of pronotal foveae punctate; elytral punctures deep and serially contiguous, intervals zig­zag; elytral setae narrow (Fig. 58) .... ............................................................................................................ perpunctus n. sp.

­ Margins of pronotal foveae very discrete, not obscured by punctures; elytral intervals more discrete; elytral setae subsquamose (Fig. 60) ........................... rhombus n. sp.

Figures

FIGURE 1. Gymnochthebius australis, lectotype. Dorsal and lateral habitus.

FIGURE 3. Gymnochthebius setosus, holotype. Dorsal and lateral habitus.

FIGURE 5. Gymnochthebius angulonotus, holotype. Dorsal and lateral habitus.

FIGURE 7. Gymnochthebius truncatus, holotype. Dorsal and lateral habitus.

FIGURE 9. Gymnochthebius lividus, holotype female. Dorsal and lateral habitus.

FIGURE 11. Gymnochthebius notalis, holotype. Dorsal and lateral habitus.

FIGURE 13. Gymnochthebius clarki, holotype female. Dorsal and lateral habitus.

FIGURE 15. Gymnochthebius wattsi, holotype. Dorsal and lateral habitus.

FIGURE 17. Gymnochthebius semicylindrus, holotype. Dorsal and lateral habitus.