Plectrocnemia cevennensis, Coppa, 2011

Waringer, Johann & Coppa, Gennaro, 2021, Identification and morphology of two polycentropodid caddisfly larvae from the Cevennes and the French and Italian Alps: Plectrocnemia cevennensis Coppa 2011 and Plectrocnemia praestans McLachlan 1884, Zootaxa 4985 (2), pp. 269-276 : 270-273

Description of the 5th-instar larva of Plectrocnemia cevennensis

Biometry. Body length of 5th-instar larva 16.6–18.9 mm, head width 1.98–2.18 mm (n = 7).

Head. Head capsule prognathous, almost as wide as long, maximum head width at height of frontoclypeal seta #6, then strongly tapering to occiput ( Fig. 1 ). Surface smooth, coloration brownish yellow, with dark brown muscle attachment spots creating circular pattern on frontoclypeal apotome center; in addition, with pair of triple spots near anterior frontoclypeal border. On parietalia, rows of muscle attachment spots along each frontoclypeal suture, along both sides of coronal suture, scattered between eyes and occiput, and in two longitudinal rows on ventral face of parietalia and around foramen occipitale ( Figs. 1, 2 ). Frontoclypeus bell-shaped, with deep semicircular constriction anterior of frontoclypeal seta #6 and with shallow bulge medially of parietal seta #11 ( Fig. 1 ). Anteclypeus yellowish brown, with 3 white longitudinal stripes. Labrum sclerotized, pale yellow, with two darker posterolateral markings, with narrow dark anterior border and with 2 small dark spots at each side of central pit; without central pigmented mark at posterior margin ( Fig. 1 la). Fused maxillolabial sclerites ( Fig. 2 s ), anterior ventral apotome ( Fig. 2 a ) and ventral head surface yellowish brown ( Fig. 2 ). Mandibles yellowish brown to dark brown, each consisting of dorsal ( Fig. 1 d ) and ventral blade ( Fig. 1 v ) along mesal margin and one apical tooth ( Fig. 1 a ); each ventral and dorsal blade with 2 or 3 subapical teeth.

Thorax. Only pronotum sclerotized, tapering posteriorly; pronotal sclerites pale yellow, with light to medium brown muscle attachment spots arranged in large, C-shaped arc in posterior half ( Fig. 3 , within white dashed line). Posterior margin of pronotum thickened, black; anterior end of dark stripe touching pleural suture. Posterolateral pronotal corners prolonged ventrally in long pointed extensions almost meeting ventrally ( Hickin 1967). Anterior border of pronotum with widely spaced, continuous row of straight setae. In total, up to 32 setae of varying lengths distributed over each pronotal half. Prosternal horn lacking. Mesonotum and metanotum purplish, more intensively on dorsal side. Pronotal pleurites large, rhomboid, on each side with dark pleural sulcus dividing epimeron and episternum, and with large, pointed foretrochantin fused with episternum. Mid- and hind pleurites much smaller, elongate-triangular, each with sickle-shaped, pointed anterior process and with blackish ventral margin ( Fig. 3 ). Legs pale yellow, with numerous setae on coxae, trochanters, and femora; tibiae and tarsi with only small number of setae. Foretarsi distinctly more than half as long as foretibiae ( Fig. 4 ). Tarsal claws long and slender, slightly curved, pointed, each with basal spur.

Abdomen. Abdomen slightly depressed (flattened dorsoventrally), terga purplish, with thin white lateral stripes; sterna pale purplish. Gills missing. Abdominal segments I–VIII each with one pair of ventral, two pairs of dorsal setae (sa 1 and sa 2, anterior sa 1 very short) and one pair of pleural setae (sa 3); in addition, abdominal segments II–VIII each with lateral longitudinal band of 25–35 short setae, creating ‘lateral fringe.’ Dorsal sclerite lacking on abdominal tergum IX; its paired trios of posterolateral setae on each body side with outermost ( Fig. 5 o ) and median secondary setae ( Fig. 5 i ) similar in length, black primary seta long and prominent ( Fig. 5 p ). Abdominal sternum IX with paired groups of ventrolateral setae each consisting of 4 long, black primary setae ( Fig. 6 p ) among> 18 shorter secondary setae ( Fig. 6 , dotted oval), in total, of 8 long, black primary setae among> 36 shorter secondary setae.

As usual in Plectrocnemia , Polycentropus , and Holocentropus ( Rinne & Wiberg-Larsen 2017) , as well as in the North American and South American genus Cernotina (John Morse, personal communication), apex of anal prolegs with black X-shaped pattern ( Fig. 7 ). Each anal proleg consisting of soft, unsclerotized basal ( Fig. 8 so) and sclerotized apical sections ( Fig. 8 sc); basal section of anal proleg distinctly longer than apical section and with many bristles. Anal claw obtuse-angled, inner margin without teeth ( Fig. 8 a and dashed line) and without any dorsal accessory teeth.

Figures

FIGURES 1–4. Plectrocnemia cevennensis Coppa 2011, 5th-instar larva. 1, head, dorsal (a = apical tooth; d = dorsal blade; la = labrum; v = ventral blade; 6, 11 = head setae # 6, 11); 2, head, ventral (a = anterior ventral apotome; s = submental sclerite); 3, pro- and mesothorax, right lateral (dotted arc = c-shaped arc of muscle attachment spots); 4, right foreleg, anterior face (double arrow = projected half length of tibia). Scale bars: 0.5 mm.

FIGURES 5–10. Plectrocnemia spp., 5th-instar larvae. Figures 5–8, Plectrocnemia cevennensis Coppa 2011: 5, detail of last abdominal tergum, posterior view of left posterolateral section, paired trio of posterolateral setae (i = median secondary seta, o = outermost secondary seta; p = primary seta); 6, abdominal sternum IX, left ventrolateral (p = primary sternal setae; dotted oval = sternal setae); 7, distal apex of left anal proleg (dotted oval = X-figure); 8, right anal proleg, median (a = obtuse-angled anal claw; sc = sclerotized distal proleg section; so = soft basal proleg section). Figures 9–10, Plectrocnemia praestans McLachlan 1884. 9, head, dorsal (arrow = posterior dark mark on labrum); 10, head, pro- and mesothorax, right lateral. Scale bars: 0.5 mm (except Figs. 5, 7: 0.1 mm).