Apatania theischingerorum Malicky 1981

Description of the fifth instar larva of Apatania theischingerorum

Biometry. Body length of 5th instar larva ranging from 5.1 to 8.3 mm, head width from 0.82 to 0.90 mm (N = 8).

Head. Head capsule medium to orange brown, distinctly granulated, with whitish muscle attachment spots and rings around eyes (Figs. 2–5); sometimes with paler areas on frontoclypeal center, posterior and anterior of eyes (Figs. 2, 3), and around foramen occipitale (Fig. 5). Dark brown along posterior half of frontoclypeal suture and at anterior frontoclypeal corners (Fig. 2). With set of 18 pairs of primary setae (nomenclature by Wiggins 1996): 10 dorsal and 2 ventral pairs of primary setae on parietalia, frontoclypeus with 6 pairs of primary setae, 3 of them along anterior border (Figs. 2, 3). Setae 9, 14, and 15 long and conspicuous (Fig. 2); seta 15 about 0.5x to 0.75x as long as seta 14. In addition, head capsule with many short, pale and almost translucent secondary setae. Frontoclypeus bell-shaped, with deeply sunken tentorial pits at central constriction (Fig. 2). Antennae situated halfway between eyes and anterior head margin (Fig. 2, arrow). Setal ratio (= median separation 'a' of frontoclypeal setae 5 alveoli divided by distance to frontoclypeal border 'b') is> 8 (Fig. 4). Labrum medium brown apically, base black, with pale setal brush at anterolateral corners originating from whitish pads of soft cuticle; with 6 pairs of primary setae (Fig. 2). Submentum mushroom-cap-shaped, light brown, with dark brown posterior half. Ventral apotome ogival, acute posteriorly. Postgenal suture short, less than 17% of apotome length. Scraper-type mandibles black, without terminal teeth along cutting edge (Fig. 5).

Thorax. Pronotum surface distinctly granulated (Fig. 6), without transverse groove at anterior 3rd (Fig. 7), medium to reddish brown, with yellowish anterior and posterior borders (Figs. 7, 8). Posterior margins thickened and darkly striped especially at posterolateral corners (Fig. 7). Pronotal surface covered by pale, translucent, tapering setae with flexible tips, especially along anterior border (Fig. 6); in addition 8–15 longer and darker setae present at each pronotal half (Figs. 7, 8). Prosternite very pale and indistinct, prosternal horn present (Fig. 7, arrow). Mesonotum completely covered by 2 medium brown sclerites with posterolateral margins darkly sclerotized (Fig. 8). Metanotum partially covered by only 1 pair of medium brown lateral sclerites with dark brown core (sa3), with anterior groups of approximately 10 setae per sclerite (Fig. 8). Setal area 1 (sa 1, sensu Wiggins 1996) without sclerites and each with 8–12 setae. Each setal area 2 (sa 2) with 6–8 setae and 2 tiny sclerotized spots (Fig. 8). Legs yellowish to light brown with numerous setae on coxae, trochanters, and femora; tibiae and tarsi with only few setae (Figs. 9–11). Femora each with several proximodorsal setae (Fig. 11, arrows). Coxa, femur, and tibia of each foreleg (Fig. 9) wider than those of mid- and hind legs (Figs. 10–11). Additional setae present on anterior and posterior faces of all femora. Setae lacking at distal sections of trochanters on all legs. Each claw with long, pale seta originating from subapical socket (Figs. 9–11).

Abdomen. Abdominal segment I with 1 dorsal and 2 lateral fleshy protuberances (Figs. 12, 13). Setal transversal band at abdominal dorsum I interrupted at center (Fig. 12). Setal group posterior to dorsal protuberance lacking (Fig. 12). Setae lacking on each side of abdominal segment I between dorsal setal group above lateral sclerite and setae associated with lateral protuberance (Fig. 13, dotted oval). On abdominal sternum I, setal areas sa 1 and sa 2 fused, creating continuous field of setae with tiny basal sclerites; setal number is 31–37. Setal areas sa 3 each with 6–8 setae (Fig. 14). Transversely elongate, oval chloride epithelia on abdominal sterna II–VII (Fig. 14 ce).

All gills single filaments; however, 2 single filament gills sometimes present in close proximity at dorsal presegmental position, most frequently on segment II (Fig. 13, arrows). Dorsal gills present at most from segment II (presegmental position) to segment VI (postsegmental position). Ventral gills ranging from segment II (presegmental) to segment VII (postsegmental). Lateral gills lacking. Lateral fringe extending from anterior border of segment II to end of segment VII. Forked lamellae (Figs. 15f) present dorsally of lateral fringe (Fig. 15l): 3–4 lamellae on each side of segment III, 0–2 lamellae on each segment IV to VII.

Abdominal dorsum VIII with 2 long (Fig. 17, arrow) and 10 short posterodorsal setae (Fig. 17 ds). Mostly 1 posterolateral seta present on each half of abdominal dorsum IX. Tergite of abdominal segment IX ovoid, yellowish brown, with 28–32 setae, 2 central and 2 lateral setae conspicuously enlarged (Figs. 16, 17). Anal prolegs of limnephilid type, light brown, each with black bar at anterodorsal border of claw base; lateral sclerite with 5 setae along posterior edge; anal claw dark brown, without accessory hook (Fig. 16).

Case. Fifth instar larval case 5.8_ 7.8 mm long (N = 8), curved, slightly tapering posteriorly (width at anterior opening 2.5–3.4 mm and at posterior opening 1.3–1.6 mm), consisting of mineral particles of varying size, mixed with larger particles which are mostly attached laterally (Figs. 18–19).