Hydropsyche doehleri Tobias 1972

Vicentini, Heinrich, Wyler, Sofia & Waringer, Johann, 2020, The larva of Hydropsyche doehleri Tobias 1972, based on Swiss material (Hydropsychidae, Trichoptera), Zootaxa 4786 (4), pp. 535-545 : 536-540

Description of the final instar larva of Hydropsyche doehleri Tobias 1972

Biometry. Body length 15.0– 17.8 mm, head width 1.56–1.72 mm (n = 7).

Head. Head capsule prognathous, surface smooth, roundish, maximum width at mid-length, tapering anteriorly and posteriorly ( Figs. 2–5 ). Coloration chestnut brown; on parietalia, with large pale rings around eyes ( Fig. 6 ), and with yellow ventrolateral area extending from near anterior to posterior borders; posterior section of yellow area only half as wide as anterior area ( Fig. 6 ). Frontoclypeal apotome ogival, its maximum width at straight anterior border ( Fig. 2 ); anterior 2/3 of frontoclypeal suture slightly tapering posteriorly and almost parallel-sided; posterior branches of frontoclypeal suture meeting at near right angle ( Fig. 2 ). Frontoclypeal step continuous, present also at center of sclerite ( Fig. 6 , arrow). Typically, yellow patches on frontoclypeal apotome consisting of two pairs of yellow lateral patches, mesal anterior and posterior patches indistinct ( Figs. 2–4 ); in dark individuals, only anterior pair of lateral patches distinctly yellow ( Fig. 5 ). Borders of frontoclypeal apotome and lateral sections of parietalia densely covered by secondary acuminate peg setae ( Figs. 2–4 , 6 ). Ventrally, parietalia dark brown, with narrow yellow anterior border and narrow yellow band along anterior half of hypocranial suture ( Fig. 7 ). Striae of stridulatory file within dark brown coloration ( Fig. 10 , dotted oval). Parietalia touching ventrally, thereby creating anterior ventral apotome (= submentum; sm in Fig. 7 ); posterior ventral apotome reduced. Anterior section of submentum with pronounced median division (arrow in Fig. 7 ), posterior section broadly triangular with short, wide lateral lobes (sm in Fig. 7 ). Yellowish-brown mandibles slightly asymmetrical, with black cutting edges and teeth. Each mandible consisting of dorsal and ventral blades along mesal margin, each blade with one apical tooth; each ventral blade with 3 subapical teeth along its edge, each dorsal blade with small subapical tooth and curved cutting edge ( Fig. 2 m ).

Thorax. Pro-, meso- and metanota fully sclerotized; pronotal sclerites separated by median dorsal ecdysial line, the latter lacking on meso- and metanotal sclerites ( Fig. 8 ). Transverse ecdysial suture lacking on all notal sclerites. Tergites densely covered by small bristles. Pronotal sclerite (pn in Fig. 8 ) dark brown, with black, straight posterior border. Mesonotal sclerites (msn in Fig. 8 ) with black borders and sinuate, M-shaped posterior border heavily sclerotized in median section; mesonotal surface with dark median longitudinal band and dark bands extending from anterolateral corners to center of posterior border. Metanotal sclerites (mtn in Fig. 8 ) yellowish, with black trimming along lateral border and anterolateral corners; posterior border slightly concave, with black central bar; black bands extending from anterolatereal corners to brownish area at rear center of sclerites.

Prosternal plate (a in Fig. 9 ) broadly trapezoidal, with elongate and enlarged anterolateral corners and pair of symmetrical, shallow concavities along black anterior border; with dark bar along posterior border (posterior part of a in Fig. 9 ). Intersegmental fold posterior to prosternal plate with pair of sclerites, each one consisting of dark brown rhomboidal median section (pm in Fig. 9 ) and yellowish, funnel-shaped lateral section (pl in Fig. 9 ), the latter with concave, black lateral border.

Foretrochantin (ft in Fig. 10 ) yellow, with black ventral border, forked (arrows in Fig. 10 ). Mid- and hind pleural sclerites smaller, elongate triangular, with blackish ventral margins (mps and hps in Fig. 11 , respectively). Legs yellow to yellowish brown, with numerous secondary setae on coxae, trochanters, and femora; tibiae and tarsi with smaller numbers of setae ( Figs. 10, 11 ). Each forefemur club-shaped, with broad, concave anterodorsal border apically. All femora with long ventral setal fringes. Tarsal claws long and slender, slightly curved, pointed, each with basal spur ( Figs. 10, 11 ). Prosternum without gills, gills of meso- and metasterna each with branches originating from truncate base.

Abdomen. Abdomen near white to pale purplish–blue, with coloured areas subdivided by pale bands ( Fig. 12 ; coloration may be modified by preservation), and densely covered with hairlike setae (hs in Fig. 13 ) and clavate scale hairs (sh in Fig. 13 ). Each segment with 2 pairs of groups of dorsal primary setae, including posterior subdorsal pair (sa 2 in Fig. 12 ) and dorsolateral pair (sa 3 in Fig. 12 ). In addition, with pupal gill buds [not appearing before the final (fifth) instar in Hydropsychidae ] (dotted oval in Fig. 12 ). Abdominal segments 1–6 with pair of multibranched gills matching morphology of gills on thoracic segments (g in Fig. 12 ). Lateral fringe lacking. Pair of ventral sclerites on each of abdominal segments VIII and IX yellowish brown, conical, pointing in anterior direction, with scler- ites of segment IX much larger (vs in Fig. 14 ). Segment IX with dark dorsal sclerite and pair of dark lateral sclerites (ds and ls in Fig. 15 , respectively). Segment X with anal papillae (ag in Fig. 15 ). Anal prolegs with sclerites orange, each consisting of lateral area sclerite, ventral sole plate, large, sickle-shaped anal claw, and apicodorsal brush of long setae (la, vsp, ac, and st in Fig. 15 , respectively).

Figures

FIGURES 2–5. Hydropsyche doehleri Tobias 1972, 5th instar larvae, heads, dorsal (m = mandible; dashed white lines indicate maximum width of frontoclypeal apotome and its near-right-angled apex). Scale bars: 0.5 mm.

FIGURES 6–11. Hydropsyche doehleri Tobias 1972, 5th instar larvae. 6, head, right lateral (arrow = frontoclypeal step present also at center of sclerite); 7, head, ventral (sm = submentum; arrow = submental notch); 8, thoracic nota, dorsal (pn = pronotum; msn = mesonotum; mtn = metanotum); 9, prosternum, ventral (a = anterior prosternite; pm = median posterior prosternite; pl = lateral posterior prosternite); 10, head, right ventrolateral, and forelegs, with posterior face of right foreleg (ft = fore trochantin; arrows = forks of foretrochantin; dotted oval = striae of file for stridulation); 11, right midleg and hind leg, posterior faces (ml = midleg; hl = hind leg; mps = pleural sclerite of midleg; hps = pleural sclerite of hind leg). Scale bars: 0.5 mm.

FIGURES 12–15. Hydropsyche doehleri Tobias 1972, 5th instar larvae. 12, abdominal segment VI, left lateral (g = multibranched gill; sa2, sa3 = setae of setal areas 2 and 3; dotted oval = pupal gill bud); 13, abdominal tergum V, detail of right dorsolateral section (hs = hairlike setae; sh = clavate scale hairs); 14, abdominal segments VII to X and anal prolegs, ventral (ac = anal claw; vs = paired ventral sclerites of abdominal sterna VIII and IX); 15, abdominal segments V to IX and anal prolegs, right lateral (ac = anal claw; ag = anal papillae; ds = dorsal sclerite; la = lateral area sclerite; ls = lateral sclerite; st = setal tuft; vs = ventral sclerites; vsp = ventral sole plate; arrow = gills lacking on abdominal segment VII). Scale bars: 0.5 mm (except Fig. 13: 0.1 mm).