Gyrinus species

Gustafson, Grey T. & Short, Andrew E. Z., 2017, Review of the whirligig beetle genus Gyrinus of Venezuela (Coleoptera: Gyrinidae), Acta Entomologica Musei Nationalis Pragae 57 (2), pp. 479-520 : 514-516

Key to the adult Gyrinus species of Venezuela

1 Dorsally black in color ( Figs 33–38 ), venter mostly dark – medially brown to black in color; elytron with punctures of all 11 serial striae distinguishable ( Figs 33–38 , 43, 45 ); metanepisternal ostiole present. Subgenus Oreogyrinus . ................................. 2

– Dorsally olive green in color ( Figs 1–6 ), venter lighter – yellow to orange in color; elytron with at least one (stria I) or more medial serial striae totally effaced or with strongly reduced punctures ( Figs 1–6 , 18, 20 , 25, 27 ); metanepisternal ostiole absent. Subgenus Neogyrinus . .............................................................................................. 5

2 Pronotal transverse crease strongly impressed ( Figs 33–36 , 39–40 ); pronotal and elytral lateral margins densely riffled ( Figs 39–42 ); dorsal surface not iridescent ( Figs 33–36 ); strongly sexually dimorphic, female elytra strongly reticulate laterally ( Figs 33 , 35 , 44, 46 ). .......................................................................................................... 3

– Pronotal transverse crease greatly reduced ( Figs 37–38 ); pronotal and elytral lateral margins without riffles; dorsal surface iridescent ( Figs 37–38 ); not sexually dimorphic in elytral sculpturing. ......................... Gyrinus (Oreogyrinus) iridinus sp. nov.

3 Pronotum relatively weakly wrinkled, laterally with sparserwrinkles ( Fig. 39 ); elytral lateral margin weakly interrupted in apical 1/5 by swelling (as in Fig. 41 ); aedeagus not strongly constricted in apical 1/3, more evenly attenuated towards apex, at most weakly constricted in apical 1/3. .............................................................................. 4

– Pronotum more strongly wrinkled, laterally often with many wrinkles ( Fig. 40 ); elytral lateral margin strongly interrupted in apical 1/5 by large swelling ( Fig. 42 ); aedeagus strongly constricted in apical 1/3 ( Fig. 49 ); gonocoxae curved with truncate apices ( Fig. 59 ). .................................... Gyrinus (Oreogyrinus) vinolentus sp. nov.

4 Female elytron more reticulate, nearly entirely covered in reticulation or at least to elytral interval II; male aedeagus attenuated in basal 2/3, weakly expanded laterally in apical 1/3 ( Fig. 47 ); gonocoxae not studied. Not confirmed to be in Venezuela. ................................................. Gyrinus (Oreogyrinus) colombicus Régimbart, 1883

– Female elytron less reticulate, reticulation reaching at most to elytral interval IV; male aedeagus strongly parallel sided, apex broadly rounded ( Fig. 48 ); gonocoxae relatively straight, not strongly curved, apices weakly emarginate with prominent lateral angle ( Fig. 58 ). ........................................ Gyrinus (Oreogyrinus) venezolensis Ochs, 1953

5 Body form broadly oval ( Figs 1–3, 5 ); elytra with non-uniform reticulation, lateral reticulation distinctly more strongly impressed than medially. ............................... 6

– Body form narrowly oval ( Figs 4, 6 ); elytra with more uniform reticulation, laterally not distinctly more strongly impressed. ................................................................... 8

6 Elytra with at least serial striae VIII–IX sulcate (as in Fig. 7 ); elytral apex obliquely truncate ( Figs 1 , 8 ), at most with incomplete border present laterally; ultimate abdominal tergite without strong medial acumination. ................................................... 7

– Elytra with serial striae VIII–IX at most weakly sulcate ( Fig. 10 ); elytral apex rounded, with complete border ( Fig. 11 ); ultimate abdominal tergite often with strong medial acumination................................. Gyrinus (Neogyrinus) gibbus Aubé, 1838

7 Elytral serial striae VIII–X never lineate, with distinctly separated round punctures ( Fig. 21 ); epipleural angle of elytral apex always distinct, normally with denticle ( Fig. 9 ); aedeagus with median lobe shorter than parameres, apex with broad process ( Fig. 29 ); gonocoxae short, with strongly truncate apices ( Fig. 53 ). Very widespread Neotropical species................................. Gyrinus (Neogyrinus) ovatus Aubé, 1838

– Elytral serial striae VIII–X lineate basally with ovoid punctures; epipleural angle of elytral apex always indistinct, never with denticle; aedeagus with median lobe as long as parameres, apex evenly rounded without broad process ( Fig. 30 ); gonocoxae elongate, apices laterally weakly emarginate with prominent lateral angle ( Fig. 56 ). Species known only from the Gran Sabana in southeastern Venezuela. ..................... ................................................................ Gyrinus (Neogyrinus) sabanensis sp. nov.

8 Elytral serial striae II–XI evident ( Figs 24 , 27 ), striae VI–IX sulcate with distinct round punctures ( Fig. 28 ); elytra without distinct pre-apical medial plica; elytral apex obliquely truncate, with distinct epipleural angle ( Fig. 24 ); aedeagus with median lobe exceptionally long and broad, apex truncate ( Fig. 32 ); gonocoxae shorter with strongly emarginate apices producing a strongly pointed medial angle ( Fig. 55 ). ...... .................................................................... Gyrinus (Neogyrinus) rozei Ochs, 1953

– Elytral serial striae VI–XI evident ( Fig. 22 ), striae VI–X sulcate with linear punctures ( Fig. 26 ); elytra with distinct medial pre-apical plica ( Fig. 23 ); elytral apex rounded, without distinct epipleural angle ( Fig. 23 ); aedeagus shorter than parameres, narrow, apex strongly triangular in form ( Fig. 31 ); gonocoxae more elongate with rounded apices ( Fig. 54 ). .................................... Gyrinus (Neogyrinus) guianus Ochs, 1935

Figures

Figs 29–33. Dorsal and lateral view of the aedeagus of Neogyrinus species, not to scale. 29 – G. ovatus Aubé, 1838. 30 – G. sabanensis sp. nov. 31 – G. guianus Ochs, 1935. 32 – G. rozei Ochs, 1953.

Figs 33–38.Dorsal habitus of Oreogyrinus species, scale bar = 1 mm. 33 – Gyrinus venezolensis Ochs, 1953, female. 34 – G. venezolensis, male. 35 – G. vinolentus sp. nov. female. 36 – G. vinolentus, male. 37 – G. iridinus sp. nov., female paratype. 38 – G. iridinus, male holotype.

Figs 43–46. SEM images of elytral interval reticulation and strial punctures. 43–44 – Gyrinus venezolensis Ochs, 1953. 43 – intervals II and III, striae I–III. 44 – intervals IX and X, striae VIII–X. 45–46 – G. vinolentus sp. nov. 45 – intervals II and III, striae I–III. 46 – intervals IX and X, striae VIII–X.

Figs 1–6. Dorsal habitus of Neogyrinus species, scale bar = 1 mm. 1 – Gyrinus sabanensis sp. nov. 2 – G. gibbus Aubé, 1838 from Amazonian Venezuela. 3 – G. ovatus Aubé, 1838. 4 – G. guianus Ochs, 1935. 5 – G. gibbus ‘var. apicalis’ Sharp, 1877 from Caracas valley, Venezuela. 6 – G. rozei Ochs, 1953.

Figs 18–21. SEM images of elytral interval reticulation and strial punctures. 18–19 – Gyrinus gibbus Aubé, 1838. 18 – intervals II and III, striae I–III. 19 – intervals IX and X, striae VIII–X. 20–21 – G. ovatus Aubé, 1838. 20 – intervals II and III, striae I–III. 21 – intervals IX and X, striae VIII–X.

Figs 25–28. SEM images of elytral interval reticulation and strial punctures. 25–26 – G. guianus Ochs, 1935. 25 – intervals II and III, striae I–III. 26 – intervals IX and X, striae VIII–X. 27–28 – G. rozei Ochs, 1953. 27 – intervals II and III, striae I–III. 28 – intervals IX and X, striae VIII–X.

Figs 39–40. SEM images of the pronotum showing sculpturing of wrinkles and riffles of the lateral margins, arrows indicate pronotal transverse crease. 39 – Gyrinus venezolensis Ochs, 1953. 40 – G. vinolentus sp. nov.

Figs 41–42. SEM images of the elytron of Oreogyrinus species, scale bars = 1mm, arrows indicate the pre-apical swelling interrupting the elytral lateral margin. 41 – Gyrinus venezolensis Ochs, 1953. 42 – G. vinolentus sp. nov.

Figs 47–50. Dorsal and lateral view of the aedeagus of Oreogyrinus species, not to scale. 47 – Gyrinus colombicus Régimbart, 1883, syntype (MNHN). 48 – G. venezolensis Ochs, 1953. 49 – G. vinolentus sp. nov. 50 – G. iridinus sp. nov.

Figs 51–59. Ventral view of gonocoxae of Venezuelan Gyrinus species, not to scale. 51–56 – Neogyrinus species. 51 – G. gibbus Aubé, 1838 from Caracas valley, Venezuela (FMNH). 52 – G. gibbus from Amazonian Venezuela: Amazonas stream along Rio Sipapo (KBMC). 53 – G. ovatus Aubé, 1838 from Venezuela: Falcón: W. Curimagua, Blackwater Lagoon.54 – G. guianus Ochs, 1935 from Amazonian Venezuela:Amazonas:river near Orinoco /Sipapo confluence (KBMC). 55 – G. rozei Ochs, 1953. 56 – G. sabanensis sp. nov. 57–59 – Oreogyrinus species: 57 – G. iridinus sp. nov. 58 – G. venezolensis Ochs, 1953. 59 – G. vinolentus sp. nov.

Figs 7–11. 7–9 – SEM images of Gyrinus ovatus Aubé, 1838 elytral morphology. 7 – elytron, box indicates region shown in Fig. 8, scale bar = 1 mm. 8 – elytral apex, box indicates region shown in Fig. 9. 9 – denticle of epipleural angle of elytral apex. 10–11 – SEM images of G. gibbus Aubé, 1838 elytral morphology. 10 – elytron, box indicates region shown in Fig. 11. 11 – elytral apex of G. gibbus, showing complete border.

Figs 22–24. 22–23 – SEM images of G. guianus Ochs, 1935 elytral morphology. 22 – elytron, box indicates region shown in Fig. 23, scale bar = 1 mm. 23 – elytral apex, arrow indicates medial pre-apical plica. 24 – elytron of G. rozei Ochs, 1953, scale bar = 1 mm.