Oreodytes Seidlitz, 1887

Okada, Ryohei & Alarie, Yves, 2020, Description of the immature stages of the endangered Japanese endemic Oreodytes kanoi (Kamiya, 1938) (Coleoptera: Dytiscidae: Hydroporinae) and comparison with the known larvae of Oreodytes Seidlitz, 1887, Zootaxa 4820 (1), pp. 1-18 : 2

Oreodytes Seidlitz, 1887 (sensu novo)

( Figs. 1–25 , 28–29 )

Diagnosis. Larvae of Oreodytes can readily be distinguished from those of other species of Deronectina described in detail (i.e., Deuteronectes Guignot, 1945 ; Hornectes Fery & Ribera, 2018 ; Nectoporus Guignot, 1950 ; Neonectes J. Balfour-Browne, 1944 ) (cf. Alarie & Nilsson 1996; Alarie et al. 1996; Alarie 1997) by the following combination of characters: body fusiform, narrow ( Figs 1–2 ); cephalic capsule distinctly constricted posterior to occipital suture; occipital suture present from instar I ( Fig 5 ); parietale lacking pores PAd and PAe ( Figs 5–6 ); temporal spines acute apically and strongly developed ( Fig 19 ) (instars II and III); lamellae clypeales interrupted medially for a short distance ( Fig 6 ) (instar I); antennomere 2 lacking secondary setae; antennomere 3 with a ventroapical spinula and pore ANf absent ( Figs 7–8 ); primary seta AN2 inserted subapically, either lower or at about level of ventral spinula ( Fig 8 ); maxillary cardo fused to stipes ( Fig 10 ); primary seta MX 1 inserted on maxillary stipes ( Fig 10 ); primary seta MX 5 present; prementum lacking lateral spinulae ( Figs 11–12 ); legs lacking natatory setae ( Figs 20–21 ); primary seta TR2 of trochanters present ( Fig 14 ); spinulae present on ventral margin of tibiae and tarsi ( Figs 14 , 20 ); abdomen segments VII and VIII lacking bluntly rounded secondary setae ( Fig 22 ); abdomen segment VIII strongly constricted posterior to insertion of urogomphi, and short, less than 0.20 times LLAS in instar III ( Figs 16 , 22 ); primary seta AB5 short, not extending beyond apex of siphon ( Fig 16 ); urogomphus elongate, more than 1.9 times HW (urogomphomere 1 more than 1.1 times longer than HW) ( Figs 18 , 23 ); urogomphomere 1 at least 1.7 times longer than urogomphomere 2, with an additional pore and primary setae UR2, UR3, and UR4 about subequally distant ( Fig 18 ), with secondary spine-like setae ( Fig 23 ).

Figures

FIGURES 1–4. Oreodytes kanoi (Kamiya, 1938): (1) instar II, dorsal habitus; (2) instar III, dorsal habitus; (3) pupa. A, dorsal aspect; B, lateral aspect; C, ventral aspect; (4) adult. A, male, dorsal habitus; B, female, dorsal habitus; C, median lobe of aedeagus, lateral aspect; D, paramere, lateral aspect. Scale bars = 0.5 mm in (1–2, 4C–D), 1 mm in (3, 4A–B).

FIGURES 5–6. Oreodytes kanoi (Kamiya, 1938), instar I, head capsule: (5) dorsal aspect (colour pattern not represented); (6) ventral aspect. EB, egg bursters; TP, tentorial pits. Numbers and lowercase letters refer to primary setae and pores, respectively. Scale bar = 0.1 mm.

FIGURES 7–13. Oreodytes kanoi (Kamiya, 1938), instar I, head appendages: (7–8) antenna, (7) dorsal aspect; (8) ventral aspect; (9–10) maxilla, (9) dorsal aspect; (10) ventral aspect; (11–12) labium, (11) dorsal aspect; (12) ventral aspect; (13) mandible, dorsal aspect. Numbers and lowercase letters refer to primary setae and pores, respectively. Scale bar = 0.1 mm.

FIGURES 14–18. Oreodytes kanoi (Kamiya, 1938), instar I: (14–15) metathoracic leg, (14) anterior aspect; (15) posterior aspect; (16–17) last abdominal segment, (16) dorsal aspect; (17) ventral aspect; (18) urogomphus, dorsal aspect. Numbers and lowercase letters refer to primary setae and pores, respectively; filled squares refer to additional setae and pores. Scale bars = 0.1 mm.

FIGURES 19–23. Oreodytes kanoi (Kamiya, 1938), instar III: (19) head capsule, dorsal aspect (colour pattern not represented); (20–21) prothoracic leg, (20) anterior aspect; (21) posterior aspect; (22) last abdominal segment, dorsal aspect; (23), urogomphus, dorsal aspect. Scale bars = 0.5 mm.

FIGURES 24–25. Oreodytes kanoi (Kamiya, 1938), pupa: (24) dorsal aspect; (25) ventral aspect. A, male; B, female. Scale bar = 1 mm.

FIGURES 26–29. Habitats of larvae and pupae of Oreodytes kanoi (Kamiya, 1938): (26) Tôshichi Onsen, Iwate Prefecture, small stream; (27) habitat of pupae; (28) prepupa; (29) pupa in case. Scale bars = 1 mm.