Description of the larvae of four Japanese Platambus Thomson, 1859 (Coleoptera: Dytiscidae: Agabinae) with phylogenetic considerations Author Okada, Ryohei Author Alarie, Yves Author Michat, Mariano C. text Zootaxa 2019 2019-07-25 4646 3 401 433 journal article 25592 10.11646/zootaxa.4646.3.1 cd8c1df0-d3cd-4d23-804a-54b2ca87f63a 1175-5326 3351180 D9362795-F949-4A1F-9E46-1A466EDD9301 Description of the larvae of Platambus fimbriatus ( Sharp, 1884 ) Source of material. 1 instar I, 1 instar II, 10 instar III, Japan : Echi riv., Tanesato, Notogawa-cho, Shiga Pref. , 22.II.2015 ; 20.XII.2015 ; 10.I.2016 ; R. Okada leg; 5 instar I, 1 instar II, Japan : Abukuma riv., Tsuruo , Saigo-mura , Fukushima Pref. , 8.I.2017 R. Okada leg. Larvae were identified ex societate imaginis . Both Platambus fimbriatus and P. pictipennis occur at these two localities. Larvae of P. fimbriatus , however, could readily be recognized using features listed below. Diagnosis. First instar larva of P. fimbriatus can be distinguished from the other species studied by the following combinations of features: frontoclypeus with less than 10 spatulate setae ( Fig. 29 ); seta FR3 shorter than seta FR2 ( Fig. 29 ); seta PA6 subequal in length to seta PA7 ( Fig. 29 ); primary seta LA10 inserted subapically ( Fig. 36 ); setae TI2, TI3, TI6, TI7, TA6, and TA7 bluntly pointed apically; seta UR4 not inserted contiguously to setae UR2 and UR3; ratio L3/HW <2.90. In addition to color patterns of head capsule ( Fig. 59 ), last abdominal segment, and urogomphi ( Figs 71 , 73–82 ), the total number of spatulate setae on frontoclypeus, secondary setae on pro- and mesofemur, and the presence/absence of ventral setae on protarsus ( Table 2 ) are helpful at discriminating later instars. Instar I ( Figs 29–42 , 74 ). Color. Dorsal surface of head capsule predominantly dark brown; frontoclypeus yellowish anteriorly, dark brown around each egg burster; parietale dark brown, pal- er over occipital region; head appendages pale yellow, A3, A4, MP3, MP2, MP3 and LP2 infuscate apically; thoracic and abdominal terga I to VII pale brown; LAS predominantly dark brown; urogomphi pale yellow basally, dark brown over distal half; legs predominantly pale yellow, dark brown apically. Body. Measurements and ratios that characterize the body shape are shown in Table 3 . Head. Head capsule ( Figs 29–30 ). Rounded, sides slightly diverging posteriorly; frontoclypeus with 10 spatulate setae. Antenna ( Figs 31–32 ). A3’ finger-like. Chaetotaxy. Seta FR3 shorter than seta FR2; seta PA6 subequal or longer than seta PA7; seta PA13 shorter than PA12; prementum with one additional seta on dorsal surface; setae TI2, TI3, TI6, TI7, TA6, and TA7 bluntly pointed apically; seta AB2 shorter than seta AB9; seta AB15 longer than seta AB11; seta UR4 not inserted contiguously to setae UR2 and UR3; position and number of additional setae on legs are shown in Table 1 . Instar II ( Fig. 77 ). As first-instar larva except as follows: Color. Dorsal surface of LAS yellowish anteriorly, dark brown over posterior half. Body. Measurements and ratios that characterize the body shape are shown in Table 3 . Head. Head capsule. Frontoclypeus with 20–21 spatulate setae. Antenna. A3’ bulge-like. Chaetotaxy. Position and number of secondary setae on legs are shown in Table 1 ; parietale with 4 spine-like secondary setae on lateral margin of each side; anterodorsal secondary setae on TI and TA bluntly pointed apically. Instar III ( Figs 59 , 65–66 , 71 , 80 ). As second-instar larva except as follows: Color. Dorsal surface of head capsule yellowish; parietale yellowish with a narrow V-shaped dark brown marking across capsule at about mid-length and some brown maculae posteriorly; pro- and mesotergum and abdominal segments yellowish with several brown maculae, metanotum predominantly dark brown; LAS yellowish anteriorly, dark brown over distal 1/3 to 1/2; urogomphi predominantly yellow. FIGURES 29–30. Platambus fimbriatus ( Sharp, 1884 ) , instar I, head capsule: (29) dorsal aspect (colour pattern not represented); (30) ventral aspect. EB, egg bursters; TP, tentorial pits. Numbers and lowercase letters refer to primary setae and pores, respectively. Scale bar = 0.10 mm. FIGURES 31–37. Platambus fimbriatus ( Sharp, 1884 ) , instar I, head appendages: (31–32) antenna, (31) dorsal aspect; (32) ventral aspect; (33–34) maxilla, (33) dorsal aspect; (34) ventral aspect; (35–36) labium; (35) dorsal aspect; (36) ventral aspect; (37) mandible, dorsal aspect. Numbers and lowercase letters refer to primary setae and pores, respectively; filled squares refer to additional setae. Scale bars = 0.10 mm. FIGURES 38–42. Platambus fimbriatus ( Sharp, 1884 ) , instar I: (38–39) metathoracic leg; (38) anterior aspect; (39) posterior aspect; (40–41) last abdominal segment; (40) dorsal aspect; (41) ventral aspect; (42) urogomphi, dorsal aspect. Numbers and lowercase letters refer to primary setae and pores, respectively; filled squares refer to additional setae. Scale bars = 0.20 mm in (38–39), 0.10 mm in (40–42). Body. Measurements and ratios that characterize the body shape are shown in Table 3 . Head. Head capsule ( Fig. 59 ). Frontoclypeus with 26–31 spatulate setae. Chaetotaxy . Position and number of secondary setae on legs are shown in Table 1 ; parietale with 6–8 spine-like secondary setae along lateral margin. Habitat. Larvae occur along quiet margins of moderate sized rivers flowing on sandy bottom. First-instar larvae are mainly collected along the banks under stones in shallow water. Whereas also collected in shallow parts, both second- and third- instar larvae appear to be more abundant in dry grass deposits ( Fig. 85 ).