Copelatus masculinus Régimbart, 1899

Source of material. The five instar II and five instar III larvae studied were reared ex ovo from adults collected at the following locality: Japan. Tarumai-shitsugen, Yonaguni-cho Yonaguni-jima Island, Okinawa Prefecture, 24°26’31.2’’N 122°58’06.2’’E, 17.VI.2018; K. Watanabe leg.

Diagnosis (instar III). The third instar of Copelatus masculinus can easily be distinguished from that of the other species studied in this paper by the following combination of characters: HL = 1.00 mm; L3 <2.00 mm; U <0.40 mm; head capsule rounded, slightly constricted at level of occipital region (Fig. 25), scale-like sculpticels present over frontoclypeus and parietale; anterior margin of frontoclypeus narrowly convex, extending mesally slightly beyond adnasalia (Fig. 25); adnasalia margined with short bluntly rounded teeth (Fig. 64); MP2/MP1> 1.50; GA/MP1> 1.50; LP2/LP1 <1.10; 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; Oriental and Palaearctic.

Description, instar II

Body: Measurements and ratios aimed to characterize body shape are shown in Table 4.

Head: Head capsule rounded, slightly constricted at level of occiput; anterior margin of frontoclypeus narrowly convex, extending mesally slightly beyond level of adnasalia; scale-like sculpticels well-developed over frontoclypeus and parietale; adnasalia margined with short bluntly rounded teeth (see Fig. 64); HL = 0.68–0.72 mm; A/MP = 1.33–1.36; MP/LP = 1.99–2.07; MP2/MP1 = 1.62–1.72; GA/MP1 = 1.92–2.13; LP2/LP1 = 1.33–1.55; MNL/MNW = 2.83–3.33.

Thorax: L3 = 1.32–1.42 mm.

Abdomen: LAS = 0.46–0.54 mm; LAS subcylindrical to subconical, not constricted posteriorly at point of insertion of urogomphi. Urogomphus: U = 0.23–0.25 mm, composed of two urogomphomeres; U/HW = 0.32–0.34; U/LAS = 0.46–0.51.

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

Description, instar III (Figs 25–27, 64). As second-instar larva except as follows:

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

Head (Figs 25, 27, 64): HL = 0.97–0.99 mm; A/MP = 1.34–1.37; MP/LP = 2.04–2.14; MP2/MP1 = 1.51–1.65; GA/MP1 = 1.61–1.85; LP2/LP1 = 1.06–1.12; MNL/MNW = 2.84–2.92.

Thorax: L3 = 1.90–2.00 mm.

Abdomen (Fig. 26): LAS = 0.75–0.77 mm; U = 0.31–0.32 mm, U/HW = 0.29–0.31; U/LAS = 0.40–0.43.

Chaetotaxy: Parietale with 7–9 temporal spines; position and number of secondary setae on legs are shown in Table 7.