Larval morphology of the Japanese species of the tribes Acidocerini, Hydrobiusini and Hydrophilini (Coleoptera: Hydrophilidae) Minoshima, Yûsuke Hayashi, Masakazu Acta Entomologica Musei Nationalis Pragae 2011 suppl. 2011-06-30 51 1 118 39W8Q Sharp, 1884 Sharp 1884 [360,917,1215,1240] Insecta Hydrophilidae Enochrus Animalia Coleoptera 40 37 Arthropoda species umbratus Holcophilydrus  ( Figs. 1C, 6A, 19–21, 28D, 44B, 45B)   Material examined.   JAPAN: HOKKAIDÔ:2 L3, Shinoro, Sapporo-shi,  26.vi.2009,YM; 6 L3, Kamishinoro, Shinorochô, Sapporo-shi, N43°08.38´, E141°22.27´,  11.vii.2009, YM.  General morphology. Third instar. Colour. Head and sclerotised parts light yellowish brown; membranous parts milky to slightly greyish white ( Fig. 1C).  Head( Figs. 19A, 20). Frontal lines slightly lyriform. Nasale serrate. Right epistomal lobe strongly projecting about as far as nasale; left lobe strongly projecting, not projecting further than nasale; lateral sides of anterior margin of epistome emarginate.  Antenna( Fig. 21A) short, slightly slender. Scape slightly longer than pedicel. Pedicel with inner membranous area completely surrounded by sclerite situated on apical 0.18 of inner face of sclerite.  Fig. 19.  Enochrus( Holcophilydrus) umbratus Sharp, 1884, third instar.A – head, dorsal view; B – spiracular atrium, dorsal view.  Mandibles( Figs. 21B–C) asymmetrical; left mandible with one moderately large inner tooth, the tooth slightly serrate; inner edge of mandibular apex serrate.  Maxilla( Figs. 21D–E): Maxillary palpomere 1 about as long as palpomere 4, palpomere 2 the shortest, palpomere 3 slightly shorter than palpomere 4.  Labium( Figs. 21F–G): Mentum subquadrate, with small cuticular spines on basal half of dorsal surface. Ligula about as long as labial palpomere 1. Labial palpi much shorter than mentum, covered with narrow cuticular spines on intersegmental membrane between palpomeres 1 and 2, and on dorsal surface of sclerite of palpomere 2.  Abdomen. Abdominal segments 2 to 7 similar to segment 1 but anteromedian part with only one small, oval dorsal sclerite on each side; lateral sclerites narrow, very small; segments 3 to 7 with spinose prolegs, spines of prolegs stout, strongly curved at apex ( Fig. 28D).  Spiracular atrium( Fig. 19B): Segment 8 with large, oval dorsal plate; posterior edge of sclerite slightly emarginate medially; procercus incompletely sclerotised, with two long and one rather short setae.  Chaetotaxy of head. Third instar. Frontalealtogether with 42 primary sensilla and two secondary sensilla ( Figs. 20A, C). One short secondary seta at midlength between FR1 and FR5. Rather short setae ( FR5 and FR6) behind antennal socket. Second seta of gFR1 of right side shorter than others. Anterior margin of epistomal lobes each with two setae and one pore-like sensillum (gFR2). Two setae ( FR9 and FR10) and one pore-like sensillum ( FR14) situated medioanteriorly to antennal socket; FR9 moderately long; FR10 rather short. Each epistomal lobe with three sensilla; location of sensilla asymmetrical; FR12 between FR11 and FR13 on right side; FR12 behind FR13 on left side.  Fig. 20. Head capsule of  Enochrus( Holcophilydrus) umbratus Sharp, 1884, third instar.A – dorsal view; B – ventral view; C – detail of anterior margin of head capsule, dorsal view.  Parietalewith 30 sensilla and several secondary sensilla each ( Figs. 20A–B). PA1–2 and PA4–5 forming longitudinal row; PA3 close to PA4, lying laterally of the latter. Three to four short secondary setae situated along frontal line, between PA6 and PA7 but medially of line connecting PA6 and PA7. PA10 situated laterally of line connecting PA7 and PA8. One moderately long secondary seta between PA8 and PA9; one rather short secondary seta situated slightly mediad of PA8. One short secondary seta close to PA10, but sometimes absent. Two rather short secondary setae close to outer margin of antennal socket. One short secondary seta slightly behind PA21; one short secondary seta slightly behind PA15; one rather short secondary seta slightly medioposteriorly to PA13; two rather short setae close to PA15–17, one between PA15 and PA16, the other anterior to PA17; one rather short secondary seta located anteriorly to PA18; one moderately long secondary seta between PA18 and PA28 close to PA18. PA14 rather short seta; PA13, PA16 and PA18 long setae. PA11 short seta. PA23 more distant from PA24–25 than the latter from each other, close to PA22.  Fig. 21.  Enochrus( Holcophilydrus) umbratus Sharp, 1884, third instar.A – antenna, dorsal view; B–C – mandibles, dorsal view; D – maxilla, dorsal view; E – maxilla, ventral view; F – labium, dorsal view; G – labium, ventral view.  Antenna( Fig. 21A): AN2 on distal fourth of antennomere 1. Antennomere 2 with one very small secondary sensillum on basal margin of dorsal surface of sclerite; setae AN10–11 on inner membranous area surrounded by sclerite; SE1 small. Apical sensilla (gAN) with one long trichoid seta, two rather long setae, and several short setae.  Mandible( Figs. 21B–C): Outer face of mandible with three small secondary setae; one on median part close to MN4; two on basal fourth; three to four rather short secondary setae on basal part of mandible.  Maxilla( Figs. 21D–E): Outer face of stipes with two long secondary setae; one on apical part of sclerite, one on basal third of sclerite. MX2 on basal third; MX3 on basal two-fifths. MX23 at midlength of outer face of sclerite; MX20 on subapical part of outer face; MX21–22 situated ventrally on inner part of sclerite; PA22 behind PA21.  Labium( Figs. 21F–G): Dorsal surface of mentum with four rather short, stout secondary setae on lateral face; one pair of short, stout secondary setae situated anteromedially close to distal margin; ventral surface with one short secondary seta on anterior corners. LA8 at midwidth and on posterior third of prementum, on borderline of sclerite and membranous area between prementum and palpi. Apical membranous area of palpomere 2 with one rather long seta and several short setae (gLA).  Habitat.Standing or very slowly flowing water. Larvae were found in water.  Identification.This species is distributed in eastern Japan, and co-occurs with  Enochrus( Methydrus) vilis( Sharp, 1884)in the collecting site in Sapporo, Hokkaidô. The adults of  E. umbratusare much larger than those of  E. vilisand the same may be expected of their larvae. Hence, for this study we have used only the largest third instar larvae collected at the locality – they are all too large to belong to  E. vilisand may therefore be clearly associated with  E. umbratus. 2981890326 [330,879,1288,1308] 2009-06-26 Japan Sapporo-shi Shinoro 40 37 1 Hokkaido 2981890329 2009-07-11 Japan Kamishinoro 43.139668 Sapporo-shi 11 141.37117 Shinorocho 40 37 1 Hokkaido