General morphological characteristics of the instar III larvae of Mystonectes Fery & Ribera, 2018

Diagnosis: Instar III larvae of Mystonectes can readily be distinguished from those of other genera of Deronectina described in detail (i.e., Deuteronectes Guignot, 1945, Deronectes Sharp, 1882, Hornectes Fery & Ribera, 2018, Leconectes Fery & Ribera, 2018, Nectoporus Guignot, 1950, Neonectes J. Balfour-Browne, 1944, Oreodytes Seidlitz, 1887, and Scarodytes Gozis, 1914 .) by the following combination of characters: lateral margin of nasale convex along posterior half (Figs 4, 18); dorsal surface of prementum not fully sclerotized (Fig. 12); lateral margin of prementum with elongate spinulae (Figs 12–13); ratio L3/HW> 3.40 (Table 1); natatory setae along dorsal margin of femora, tibiae, meso- and metatarsi present (Figs 14–15, 20–21), present (one only) or absent on protarsus; urogomphal annuli present (Fig. 6); ratio U1/U2> 4.00 (Table 1); ratio U1/HW> 2.50 (Table 1).

Description, instar III (Figs 3–15, 17–21)

Body (Figs 3, 17): Fusiformate, narrow. Measurements and ratios that characterize the body shape are shown in Table 1.

Head (Figs 4–13, 18): Head capsule (Figs 4, 18) pear-shaped, longer than broad, maximum width posterior to stemmata at about level of occipital suture, with neck constriction distinctly delimited; ecdysial line well marked, coronal line short; occipital foramen broadly emarginate ventrally; frontoclypeus bluntly rounded, lateral margin of nasale convex along posterior half; ventroapical margin of frontoclypeus with 31–35 spatulate setae [= lamellae clypeales of Bertrand (1972)], not interrupted medially; gular suture not visible; ocularium present, stemmata not visible ventrally; tentorial pits visible medioventrally. Antenna (Figs 7–8) elongate, four-segmented, about half as long as HW; A4 the shortest, A2 and A3 the longest, subequal in length, A3 with a ventroapical spinula, A3’ short. Mandible (Fig. 9) falciform, curved inward and upward apically; mandibular channel present. Maxilla (Figs 10–11) with cardo fused to stipes; stipes short, narrow; galea and lacinia absent; MP elongate, three segmented, slightly shorter than antenna, MP1 the longest, MP3 the shortest. Labium (Figs 12–13) with prementum small, subquadrate to subtrapezoidal, slightly longer than broad, with elongate lateral spinulae, anterior margin slightly sinuated medially; LP slightly shorter than MP, two segmented, LP2 shorter than LP1.

Thorax (Figs 3, 14–15, 17, 20–21): Pronotum trapezoidal dorsally, ovate laterally, widest at posterior margin; subequal to meso- and metanotum combined; pronotum without transverse carina; both meso- and metathoracic terga with an anterotransverse carina; sagittal line visible on the three tergites; thoracic sterna membranous; mesothorax with a spiracular opening on each side. Legs (Figs 14–15, 20–21): long, composed of six segments (including pretarsus), L1 the shortest, L3 the longest; CO robust, elongate, TR divided into two parts, FE, TI and TA slender, subcylindrical; pretarsus with two long, slender, slightly curved claws, posterior claw shorter than anterior one on L1 and L2, claws subequal in length on L3; claws lacking basoventral spinulae; TI and TA with elongate spinulae along ventral margin, less developed on metatarsus.

Abdomen (Figs 3, 5–6, 17, 19): Eight-segmented, segments I–VI sclerotized dorsally, membranous ventrally; segments VII–VIII completely sclerotized, ring-like; tergites I–VII narrow, transverse, rounded laterally, without sagittal line, with anterotransverse carina, with long setae along lateral and posterior margins; segments I–VII with a spiracular opening on each side; segment VIII (= LAS) (Figs 5, 19) short, subtrapezoidal, lateral margin subparallel, slightly converging from base to point of insertion of urogomphi, abruptly converging thereafter, with anterotransverse carina dorsally and laterally; siphon short, bluntly rounded to acute apically. Urogomphus (Fig. 6) elongate, two-segmented; U1 much longer than LAS, with several non-sclerotized annuli.

Chaetotaxy (Figs 4–15, 18–21): Head capsule with numerous secondary setae; lateroventral margin of PA with 6–8 spine-like secondary setae; primary seta PA3 elongate, much longer than setae PA1 and PA2 (Figs 4, 18); AN, MX, and LA lacking secondary setae; MN with one hair-like secondary seta on basoexternal margin; thoracic and abdominal sclerites with numerous secondary setae; natatory setae present on dorsal margin of femora, tibiae, and tarsi (Figs 15, 21); secondary leg setation detailed in Table 2; urogomphomere 1 with several secondary setae (Fig. 6).