Schizopelex huettingeri Malicky 1974

Description of the final instar larva of Schizopelex huettingeri Malicky 1974

Biometry. Body length ranging from 11.4 to 11.9 mm, head width from 1.59 to 1.75 mm (n = 3).

Head. Head capsule nearly round, dorsally medium to chestnut brown, posterolaterally and ventrally yellowish white, with smooth surface and large, pale muscle attachment spots (Figs. 1–3). Distinct white semicircle beneath each eye (Figs. 1, 3). Dorsolateral ridge extending from posterodorsal corner of white semicircular ring around each eye (Fig. 3) to anterior parietal margin where ridge creating inward-bent conical projection bearing antenna (Fig. 1, arrow). Frontoclypeus narrow and elongated, with shallow central constriction and subapical bulge (Fig. 1). Head capsule with complete set of 18 pairs of primary setae: 10 dorsal and 2 ventral primary setae on each parietal, 6 pairs of primary setae on frontoclypeus. Labrum medium brown, narrowly rectangular, with 3 pairs of primary setae. Submentum broadly triangular, light brown, with dark brown anterior transverse band (Fig. 2). Mandible bases yellowish brown, distal sections black, of shredder type, right mandible with terminal tooth and up to 3 teeth along mesal edge, left mandible slightly serrate (Fig. 1).

Thorax. Anterior section of pronotum medium to dark brown, posterior section yellowish brown to medium brown, with pale muscle attachment spots. Pronotum without transverse ridge (present in other caddisfly taxa; e.g., Limnephilinae), heavily sclerotized, with anterolateral corners elongated and pointed; pair of plates meeting mesally in narrow, straight suture; surface smooth (Figs. 3, 5). Ventrolateral pronotal margin straight (Fig. 3, dotted line). Each pronotal half covered by 160–180 setae concentrated on anterior, darker pronotal section; setal type 1 pale, flexible and procumbent, setal type 2 long, straight and medium to dark brown. Anterior pronotal margin with single row of setae of both types (Figs. 3, 5). Anterior part of coxopleurite long and corniform (Figs. 3, arrow, 4). Prosternal sclerites and prosternal horn lacking.

Mesodorsum covered by 4 sclerotized plates (2 large central, 2 small lateral), whitish, with pale yellow muscle attachment spots, distinct anterior margin, less-distinct posterior margin (Figs. 5 ms, 6cs, 6ls); suture between central and lateral plates inconspicuous (Fig. 6, arrows). Setal counts per central sclerite are 75–85 in anterior group and 25–30 in posterior group (Fig. 5 ms); lateral sclerite with 45–50 black setae (Fig. 6 ls).

Metadorsum covered by colourless and barely visible, weak sclerites arranged in 2 parallel transverse bands. Setal counts per sclerite: 44–48 setae in anterior group, 20–25 setae in posterior group (Fig. 5 mt).

Legs medium to light brown (Figs. 7–9). Forelegs short and stout, each with proximal section of femur enlarged and flattened, strongly narrowing apically, thereby creating edge interacting with tibia when bent inwards (Fig. 7). Coxa with ventral group of long black setae, trochanter with dense ventral brush of pale, flexible setae. Dorsal edge of femur with large groups of proximodorsal and distodorsal black setae. Tibia with groups of long black dorsal and ventral setae and with pale apical spine. Strong tarsal claw sickle-shaped, with stout pale basal spine. Midlegs much more slender, coxae weakly sclerotized, femora not enlarged. Hind legs even more slender, tarsal claws elongated, setation less than on other legs (Figs. 7–9).

Abdomen. Abdominal segment I with pair of flat, oblique lateral and 1 low, inconspicuous dorsal protuberances (Fig. 11); setation consisting of 1 pair of ventral sa 1 setae (Fig. 10, arrows) and 1 lateral protuberance seta per side (Fig. 10 lp). Gills consisting of tiny single filaments and in presegmental position only. Dorsal gills present at most on abdominal segments I to IV, ventral gills on segments III to VII and lateral gills on II to III. Lateral fringe lacking; however, with lateral row of tiny serrate lamellae on each side of abdominal segments III to VII (Fig. 12), and with row of forked lamellae on each side of segment VIII (Fig. 13).

Dorsal sclerite of abdominal segment IX lacking, soft cuticle with 18–41 black setae of almost equal length on posterodorsal border (Figs. 14, 15 pds). Dorsum of each anal proleg with cluster of 30–40 black setae (Figs. 14, 15 aps). Weakly sclerotized lateral sclerite of each anal proleg with 22–25 black setae of varying length (Fig. 15 ls). Anal proleg claws each with sharply angled crook and dorsal accessory hook (Fig. 15, arrow).

Larval case. Cylindrical, tapering, strongly curved, made of flat sand grains of uniform size arranged in puzzle-like pattern, thereby creating rather smooth surface (Fig. 16). Case length 11.5 to 13.1 mm, anterior width 2.7 to 2.8 mm, posterior width 1.8 to 1.9 mm (n = 3). Posterior foramen partly closed by slightly conical, silken membrane with round central hole 0.55 mm in diameter (Fig. 17).