Mesophylax impunctatus subsp. aduncus

Description of the final instar larva of

Mesophylax impunctatus aduncus (Navás 1923)

(Figs 15–24)

Biometry. Body length of 5th instar larva 16.1–16.2 mm, head width 1.32–1.36 mm (n = 2). All morphological characters identical to those of Limnephilus minos except as noted below.

Head. Head capsule light brown, with medium brown, conspicuous muscle attachment spots (Fig. 15). Labrum medium brown (Fig. 15). Ventral apotome very narrow, elongate, medium brown; postgenal suture approximately 15–17% of apotome length (Fig. 16 va). Mandibles black, without terminal teeth, and without ridges in central concavity (Fig. 15, arrow).

Thorax. Pronotum (Fig. 17 p) yellow, with light brown muscle attachment spots. In total, 55–68 dark setae of varying lengths distributed over each pronotal half. Yellow central prosternite conspicuous, outlined like a flying bird’s silhouette: slightly pointed at anterior center, with pointed winglike lateral sections and fan-shaped, brown posterior extension (Fig. 18 ps). Mesonotum (Fig. 17 ms) yellow, with dark brown muscle attachment spots. Lateral and posterior margins strongly sclerotized, creating continuous black frame of mesonotum extending to anterolateral corners (Fig. 17 ms). Anterior mesonotal setal group sa 1 each with 12–15 setae, posterior group sa 2 each with 10–13 setae, lateral group sa 3 each with 16–21 setae (Fig. 17). Metanotal sclerites sa 1 yellow, transversely narrow and wide; with 8–10 setae per sclerite and additional small group of 3–4 setae lateral of each sclerite (Fig. 17 sa 1). Yellow sclerites of sa 2 with 6–8 setae per sclerite (Fig. 17 sa 2) and with small group of setae between them (Fig. 17, dotted oval). Yellow sclerites of sa 3 with dark brown muscle attachment spots, each with 16–23 setae (Fig. 17 sa 3); with small group of setae on each side between sa 2 and sa 3. Mesosternum with 4–8 dark setae, metasternum with 15–26 dark setae (Fig. 18 mss, mts). Legs yellowish brown, femora of 2nd and 3rd legs each with one proximodorsal seta, with additional setae on anterior and posterior faces (Fig. 19, dotted oval), and with 4–7 ventral-edge setae (Fig. 19, arrows). Proximal section of each mid- and hind trochanter with additional setae.

Abdomen. Abdominal segment I dorsal sa 1 and sa 2 confluent on each side, with 9–16 setae; sa 3 with 4–8 setae each, with very tiny brown basal sclerites (Fig. 17). Abdominal sternum I on each side with 14–17 setae in sa 1, 18–24 setae in sa 2, and 5–7 setae in sa 3 (Fig. 18). 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 present from segment II (postsegmental) to segment IV (pregmental). Chloride epithelia lacking. Number of posterodorsal setae on abdominal segment VIII 10–12, with 8 long and remainder short (Fig. 21 pds); with 1–2 posterolateral setae (Fig. 21 pls). Abdominal tergite IX yellow, with dark brown muscle attachment spots (Fig. 21); posterior border with 10–12 long and several shorter setae (Fig. 21). With small groups of setae on both sides of anal slit (Fig. 22, dotted oval).

Case. Fifth instar larval case 13.9–14.7 mm long (n = 2), straight, slightly tapering posteriorly (width at anterior opening 3.1–4.0 mm and at posterior opening 2.1–2.7 mm) (Fig. 24), consisting of mixed mineral particles.