Gyrinidae

Suksai, Benjamart, Gustafson, Grey T., Sites, Robert W. & Sangpradub, Narumon, 2021, The Gyrinidae (Coleoptera) fauna of Thailand: Key to tribes and genera, with new records and keys to species of Dineutini and Gyrinini, Zootaxa 5071 (1), pp. 97-117 : 114

Key to the tribes and genera of adult Gyrinidae in Thailand,

including species of adult Gyrinini and Dineutini

1 Dorsal surface of pronotum and elytron with pubescence; abdominal sternite VIII narrow and long....... Orectochilini , 2

- Dorsal surface of pronotum and elytron completely glabrous ( Figs. 1A–H ); abdominal sternite VIII broad and short....... 3

2 Antenna with six flagellomeres; surface of pronotum and elytron with glabrous regions medially and pubescence marginally............................................................................................... Patrus

- Antenna with nine flagellomeres; surface of pronotum and elytron without glabrous regions, entirely covered with pubescence.................................................................................... Orectochilus

3 Size smaller, length <6.0 mm; pronotum with median transverse depression; scutellum visible; elytron with 11 longitudinal striae ( Figs. 1A–B , 2A–B ).............................................................. Gyrinini , Gyrinus , 4

- Size larger, length 6.0–17.0 mm; pronotum without median transverse depression; scutellum not visible ( Figs. 1C–H ); elytron without evident longitudinal striae.............................................................. Dineutini , 5

4 Dorsally metallic in appearance lateral sides of elytra with bronzy sheen ( Fig. 1A ), intervals VI–X not sulcate............................................................................................ Gyrinus sericeolimbatus

- Dorsally iridescent in appearance ( Fig. 1B ); lateral sides of elytra without bronzy sheen, intervals VI–X strongly sulcate ( Fig. 2B )............................................................................... Gyrinus smaragdinus

5 Labrum short and broad, not triangular in form ( Figs. 1C–G ); apex of protibia without spine................ Dineutus , 6

- Labrum long and triangular in form ( Fig. 1H ); apex of protibia with spine ( Fig. 1H )......... Porrorhynchus marginatus

6 Size smaller, length 6.0– 8.2 mm; profemur of males without sub-apicoventral tooth; protibia wedge-shaped; elytral apices variously shaped........................................................................................ 7

- Size larger, length 13.4–17.0 mm; profemur of males with sub-apicoventral tooth; protibia club-shaped; elytral apices rounded ( Figs. 1E , 5F ).................................................................................. D. sitesi

7 Apex of flagellomere VI darkly colored; elytral apices without parasutural spines; lateral margin of pronotum and elytron black.............................................................................................. 8

- Apex of flagellomere VI lightly colored; elytral apices with parasutural spines ( Figs. 1F , 5J ); lateral margin of pronotum and elytron orange or yellow...................................................................... D. spinosus

8 Size smaller, length 6.0– 6.9 mm; body form narrowly oval; elytral apices with epipleural spines ( Figs. 1G , 6A ) evident in both sexes; elytral apex truncate and straight ( Figs. 1G , 6A ); protrochanter of male apically without patch of thick setae on ventral surface ( Fig. 4D )......................................................................... D. unidentatus

- Size larger, length 7.6–8.2 mm; body form oval; elytral apices of male only with epipleural spines ( Figs. 1C , 5A ), female without epipleural spines ( Figs. 1D , 5B ); elytral apex obliquely truncate ( Figs. 1C–D , 5A–B ); protrochanter of male apically with patch of thick setae on ventral surface ( Fig. 4A ).................................................... D. australis

Figures

FIGURE 1. Habitus of Gyrinini and Dineutini species: (A) Gyrinus sericeolimbatus, dorsal view, female; (B) G. smaragdinus, dorsal view, male; (C–D) Dineutus australis, dorsal view: (C) male; (D) female; (E) D. sitesi, dorsal view, male; (F) D. spinosus, dorsal view, male; (G) D. unidentatus, dorsal view, male; (H) Porrorhynchus marginatus, dorsal view, male; (I) D. sitesi, ventral view, male; (J) D. spinosus, ventral view, male. Scale bars = 3 mm.

FIGURE 2. Gyrinus smaragdinus: (A) female pronotum, median transverse depression (arrow), scale bar = 300 μm; (B) male elytra, spaced puncture (arrow), scale bar = 1 mm; (C) male elytral apex, scale bar = 300 μm.

FIGURE 4. SEM photographs of protochanters in species of Dineutus and Porrorhynchus (males): (A) D. australis, patch of thick setae (arrow), scale bar = 100 μm; (B) D. sitesi, protrochanter without setae (arrow), scale bar = 1 mm; (C) D. spinosus, setae (arrow), scale bar = 100 μm; (D) D. unidentatus, setae (arrow), scale bar = 100 μm; (E–F) P. marginatus, cluster setae (square and arrow): (E) scale bar = 500 μm; (F) scale bar = 100 μm.

FIGURE 5. Elytral apex, aedeagus and gonocoxae of species of Dineutus: (A–E) D. australis: (A–B) elytral apex, scale bar = 2 mm: (A) male; (B) female; (C–D) aedeagus, scale bar = 0.5 mm: (C) dorsal view; (D) lateral view; (E) gonocoxae, ventral view, scale bar = 0.5 mm; (F–I) D. sitesi: (F) male elytral apex, scale bar = 2 mm; (G–H) aedeagus, scale bar = 1 mm: (G) dorsal view; (H) lateral view; (I) gonocoxae, ventral view, scale bar = 1 mm; (J–M) D. spinosus: (J) male elytral apex, scale bar = 2 mm, (K–L) aedeagus, scale bar = 0.5 mm: (K) dorsal view; (L) lateral view; (M) gonocoxae, ventral view, scale bar = 0.5 mm.

FIGURE 6. Elytral apex, aedeagus and gonocoxae: (A–D) D. unidentatus: (A) male elytral apex, scale bar = 2 mm; (B–C) aedeagus, scale bar = 0.5 mm: (B) dorsal view; (C) lateral view; (D) gonocoxae, ventral view, scale bar = 0.5 mm; (E–G) P. marginatus: (E–F) aedeagus, scale bars = 1 mm: (E) dorsal view; (F) lateral view; (G) gonocoxae, ventral view, scale bars = 1 mm.