Copelatus tenebrosus Régimbart, 1880

Source of material. The single instar III larvae studied was reared ex ovo from were adults collected at the following locality: Japan. Mantaburu, Yonaguni-cho, Yonaguni-jima Island, Okinawa Prefecture, 24°27’04.1”N 122°57’36.8”E, 13.VI.2019; E. K. Watanabe leg.

Diagnosis (instar III). The third instar of Copelatus tenebrosus can easily be distinguished from that of the other species studied in this paper by the following combination of characters: HL = 0.80 mm; L3 <2.00 mm; U <0.40 mm; head capsule rounded, slightly constricted at level of occipital region (Fig. 52), scale-like sculpticels present over frontoclypeus and parietale; anterior margin of frontoclypeus narrowly convex, extending mesally well beyond level of adnasalia (Fig. 52); adnasalia margined with mostly short bluntly rounded teeth (Fig. 65); MP2/MP1> 1.50; GA/MP1> 1.50; 1.30 <LP2/LP1 <1.90; inner margin of stipes lacking a dorsal linear row of spinulae; profemur with less than 3 PV and 4 AV secondary setae; metafemur with less than 3 AV secondary setae; urogomphus composed of two urogomphomeres; U/HW <0.40; U/LAS <0.50; Australia, Oriental, Palaearctic.

Description, instar III (Figs 52–53, 65)

Body: Measurements and ratios aimed to characterize body shape are shown in Table 6.

Head (Figs 52, 65): Head capsule rounded, slightly constricted at level of occiput; anterior margin of frontoclypeus narrowly convex, extending mesally well beyond level of adnasalia; scale-like sculpticels present over frontoclypeus and parietale; adnasalia margined with mostly short bluntly rounded teeth (Fig. 65); HL = 0.84 mm; A/MP = 1.40; MP/LP = 2.03; MP2/MP1 = 1.64; GA/MP1 = 1.85; LP2/LP1 = 1.43; MNL/MNW = 2.87.

Thorax: L3 = 1.73 mm.

Abdomen (Fig. 53): LAS = 0.63 mm; LAS subconical, not constricted posteriorly at point of insertion of urogomphi. Urogomphus, U = 0.30 mm, composed of two urogomphomeres; U/HW = 0.33; U/LAS = 0.47.

Chaetotaxy: Parietale with 5–6 temporal spines; position and number of secondary setae on legs are shown in Table 7.