Helochares (Hydrobaticus) anchoralis Sharp, 1890

Minoshima, Yûsuke & Hayashi, Masakazu, 2011, Larval morphology of the Japanese species of the tribes Acidocerini, Hydrobiusini and Hydrophilini (Coleoptera: Hydrophilidae), Acta Entomologica Musei Nationalis Pragae (suppl.) 51, pp. 1-118 : 61-64

Helochares (Hydrobaticus) anchoralis Sharp, 1890

( Figs. 35–37 )

Material examined. JAPAN: KYÛSHÛ: Kagoshima-ken: 35 L1, Kasekenmata, Tatsugô-chô, Amami-ôshima I., 1.vii.2008 (fixed) (egg case carried by the adult collected in the field), MH.

General morphology. First instar. Colour. Head and sclerotised parts light yellowish brown; membranous parts milky white.

Head ( Fig. 35A ). Nasale projecting slightly further than left epistomal lobe, but not projecting further than right lobe ( Fig. 36C ). Epistomal lobes rounded, asymmetrical; right lobe projecting further than left lobe.

Antenna ( Fig. 37A ) short, rather stout. Scape slightly shorter than pedicel.

Mandibles ( Figs. 37 B–C): Distal inner teeth serrate; inner face of mandible serrate.

Maxilla ( Figs. 37 D–E): Maxillary palpomere 1 about as long as palpomere 4, palpomere 2 the shortest, palpomere 3 slightly longer than palpomere 4; palpomere 1 the widest.

Labium ( Figs. 37 F–G): Mentum longer and slightly wider than prementum, with small cuticular spines on dorsal surface. Labial palpi about as long as mentum; palpomere 1 much shorter than palpomere 2.

Thorax. Mesonotum with two dorsal sclerites on each side, each with five very long setae. Metanotum with one large dorsal sclerite on each side, each with five very long setae each.

Abdomen. Segment 1 with three visible dorsal sclerites on each side; anterior one narrow, small, posterior two very small, weakly sclerotised; each posterior sclerites with one long seta; segments 2 to 7 similar to segment 1 but dorsal sclerites very indistinct or absent.

Spiracular atrium ( Fig. 35B ): Segment 8 with large, oval dorsal plate; dorsal plate with four projections on posterior edge, inner two with two setae each; lateral part of dorsal plate with three long setae on each side, median one very long; procercus with one rather long stout seta and two rather long setae. Segment 9 trilobed; median lobe with two rather short and two moderately long setae on posterior edge; each lateral lobe with two moderately long setae on posterior edge.

Primary chaetotaxy of head. Frontale with 46 sensilla altogether ( Figs. 36A, C ). FR 2 between FR 1 and FR 3. FR 5 short seta. FR 6 moderately long scale-like seta situated laterally of line

connecting FR 5 and FR 7; FR 7 moderately long seta. Nasale with a group of six stout, short setae and two small, pore-like sensilla (gFR1). Each epistomal lobe with two short setae on inner part, and two short, scale-like setae mediolaterally (gFR2). FR 10 placed between FR 4 and FR 9, mesally of line connecting FR 4 and FR 9; one pore-like sensillum ( FR 14) situated anteriorly to inner margin of antennal socket. Location of FR 11–13 slightly asymmetrical. Right lobe with FR 11 situated anteriorly to FR 12, close to lateral seta on nasale, FR 12 situated between FR 11 and FR 13, but laterally of line connecting FR 11 and FR 13. Left lobe with FR 12 located more laterally of line connecting FR 11 and FR 13 than on right lobe.

Parietale ( Figs. 36 A–B): PA 1–5 forming slightly irregular row. PA 7 long trichoid seta; PA 12 rather long seta. PA 20 moderately long seta. PA 16 long, narrow scale-like seta situated anteriorly to PA 18, and between PA 15 and PA 17; PA 17 close to PA 16, situated anteromesally to PA 16. PA 26–28 situated ventrally on anterior and lateral 0.45 of parietale; PA 27 situated mesally of line connecting PA 26 and PA 28. Two pore-like sensilla ( PA 29–30) located ventrally on about basal fourth of parietale.

Antenna ( Fig. 37A ): Antennomere 2 with one pore-like sensillum ( AN 6) situated dorsally close to distal margin of sclerite, and five setae ( AN 7–11) on intersegmentary membrane between antennomeres 2 and 3; AN 7 rather short, rounded apically, AN 8 shorter than AN 7, rather stout, AN 9 minute; AN 7–9 on outer face of antenna next to sensorium SE 1; setae AN 10–11 on inner face of antenna; AN 10 long, narrow scale-like, AN 11 short, both setae close to each other.

Mandible ( Figs. 37 B–C): MN 2 located posteriorly to line connecting MN 3 and MN 4, between MN 1 and MN 3; MN 4 on lateral face. MN 5 small seta.

Maxilla ( Figs. 37 D–E): One pore-like sensillum ( MX 12) and two very long setae ( MX 13– 14) located ventrally on outer face of palpomere 1; MX 12–13 on outer face of distal part of sclerite; MX 12 situated more ventrally than MX 13; MX 14 situated ventrally on median part of distal margin of sclerite. MX 23 and MX 20 on distal part of outer face of sclerite of palpomere 3; MX 20 situated more ventrally than MX 23; MX 21 situated ventrally on inner part of sclerite of palpomere 3, close to distal margin; MX 22 behind MX 21; MX 24 very long, trichoid seta.

Labium ( Figs. 37 F–G): LA 1 very long.

Habitat. Adults from which the larvae were reared were found in standing water.

Identification. Larvae were reared from an egg case carried by an identified adult female.

Figures

Fig. 35. Helochares (Hydrobaticus) anchoralis Sharp, 1890, first instar.A – head, dorsal view; B – spiracular atrium, dorsal view.

Fig. 36. Head capsule of Helochares (Hydrobaticus) anchoralis Sharp, 1890, first instar.A – dorsal view; B – ventral view; C – detail of anterior margin of head capsule, dorsal view.

Fig. 37. Head appendages of Helochares (Hydrobaticus) anchoralis Sharp, 1890, first 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.