Hybogralius hartmeyeri, (REGIMBART, 1908)

Archangelsky, Miguel, Martínez Román, Nicolás Rafael & Fikáček, Martin, 2021, Larval chaetotaxy and morphology are highly homoplastic yet phylogenetically informative in Hydrobiusini water scavenger beetles (Coleoptera: Hydrophilidae), Zoological Journal of the Linnean Society 192 (2), pp. 416-416 : 416-

HYBOGRALIUS HARTMEYERI (RÉGIMBART, 1908)

( FIGS 44–53 )

Note: The larva here described has been mounted whole, therefore parts of the head capsule and ventral mouthparts are not fully visible; only characters accessible for study are described and illustrated.

Diagnosis

Larval morphology: Head capsule subquadrate, with lateral margins subparallel; frontal lines Y-shaped, incomplete; coronal line short; nasale asymmetrical, convexly projected, with five short irregular teeth, median tooth smaller; lateral lobes of epistome strongly asymmetrical, right lobe subtriangular, bearing 12 short setae on distal margin, left lobe more strongly projected with a row of 12 setae on anterolateral margin, outer six shorter, inner six setae stronger, with inner margin slightly dentate, inner margin of lobe with a row of strong cuticular projections pointing mediad; posterior tentorial grooves close to midline, anterior, close to submentum. Cervical sclerites present, subquadrate. Antenna short, basal antennomere the widest, slightly longer than second and third antennomeres combined; sensory appendage short 0.16 × as long as third antennomere. Mandibles strongly asymmetrical; right mandible slightly larger than left one, with three retinacular teeth at midlength, distal tooth larger; left mandible also with three retinacular teeth, distal one larger, subtriangular, irregularly serrated, second tooth slightly smaller, bearing several leaf-like projections pointing downward, third tooth smaller, blunt, also pointing downward; inner margin of left mandible forming a shallow groove. Maxilla with large stipes, longer than palpus, inner margin apparently lacking cuticular projections basally, distally bearing a strong and sharp spine; first palpomere incompletely sclerotized dorsally, bearing an inner appendage distinctly shorter than second palpomere, third palpomere the longest. Labium with submentum fused to head capsule, dorsally with small cuticular projections on mentum; membrane between first and second palpomeres with short cuticular projections; mentum subtrapezoidal, short, wider basally; prementum subrectangular, slightly wider apically; ligula well developed, shorter than first palpomere; second palpomere the longest, 2.2–2.5 × as long as first palpomere. Pronotal plate large, covering most of pronotum, subtrapezoidal, posterior margin wider, with rounded corners and with sagittal line; mesothorax with a pair of triangular plates, metathorax with a pair of semicircular plates on anterior margin. Abdomen membranous, segments one to seven similar in shape, subdivided into three or four transversal folds; segment eight narrower, lacking dorsal plate, subdivided in two transversal folds; segment nine short, slightly concave. Legs well developed, five-segmented. Morphometrics. See Table 3. Chaetotaxy. gFR1 with six short dorsal setae, ventral two setae missing; gFR2 asymmetrical, left side with 11 setae, inner five larger and stouter, projecting mediad, right side with 13 short setae; FR4 as a very short seta; pore PA30 behind pore PA29; A2 with one seta near SE1; pore MN4 much closer to seta MN1 than to MN5; gMX2 apparently with five setae ( MX 7–11); submentum apparently with one pair of setae (LA1), LA2 could not be found; pore LA11 distal; LA15 apparently missing.

Figures

Figures44–53. Hybograliushartmeyeri, third instarlarva.44–46,headcapsule (44,dorsally;45,ventrally;46,labroclypeus).47–48, mandibles, dorsal view (47, left mandible; 48, right mandible). 49, antenna, dorsal view. 50–51, maxilla (50, dorsal view; 51, ventral view).52, mentum and prementum, dorsal view.53, prementum, ventral view.Scale bars:Figs 44–45: 0.1 mm, Figs 46–53: 0.05 mm.