Plectrocnemia renetta, Malicky, 1975

Waringer, Johann & Malicky, Hans, 2019, The larva of Plectrocnemia renetta Malicky 1975 (Trichoptera, Polycentropodidae), including a discriminatory matrix to the larvae of Plectrocnemia Stephens 1836 species of Greece, Zootaxa 4568 (2), pp. 372-382 : 373-378

Description of the 5th instar larva of Plectrocnemia renetta

Biometry. Body length of 5th instar larvae ranging from 25.5 to 28.9 mm, head width from 2.32 to 2.57 mm (n = 3).

Head. Head capsule prognathous, surface smooth, slightly elongated in shape, posterior third tapering ( Figs. 1, 2 ). Coloration yellowish brown, with dark brown muscle attachment spots on frontoclypeus and parietalia ( Figs. 1, 2 ). Large pale ring present around eyes ( Fig. 3 ). Head capsule with complete set of primary setae (most of them visible in Fig. 1 and numbered). Frontoclypeus bell-shaped, with deep central constriction posterior of eye level; its posterior spots arranged in a half-trapezoidal pattern ( Fig. 1 , dotted line). Antennae very small, near anterior parietal border and frontoclypeal suture, consisting of pale tubercle with four pale, tiny apical setae (not visible in Fig. 1 ). Anteclypeus light brown, with three white longitudinal stripes ( Fig. 4 ). Labrum sclerotized, whitish to pale yellow, with narrow dark anterior border and distinct posterior mark ( Fig. 4 , arrow); with complete set of 6 primary setae per side. Anterior ventral apotome medium brown, very narrow, with elongated lateral lobes ( Fig. 2 a ); submental sclerite medium brown, trapezoidal ( Fig. 2 ss); maxillary lobe and palp light to medium brown ( Fig. 2 ml, mp); labial spinneret short, not extending anterior of head margin, with labial palps appressed to its sides ( Fig. 2 ls). Yellowish-brown mandibles with black cutting edges and teeth. Each mandible consisting of dorsal and ventral blade along mesal margin and one apical tooth ( Figs. 5 a, 6 a ); each ventral and dorsal blade with 3 subapical teeth along its edge except right upper blade with only 1 large subapical tooth and 1 tiny subapical tooth very close to large one ( Figs. 5, 6 , arrows). Small group of setae in central concavity of left mandible (not visible in Figs. 5, 6 ), but lacking in right mandible.

Thorax. Pronotum sclerotized, tapering posteriorly; pronotal sclerite pale yellow to yellowish brown, with medium brown muscle attachment spots ( Figs. 1, 3 ). As common in Polycentropodidae , posterior pronotal corners prolonged ventrally in long pointed processus ventrales almost meeting at midline ( Fig. 2 , arrows). Posterior and posterolateral margins of pronotum thickened and darkly striped; anterior end of dark stripe touching pleural suture ( Fig. 3 ); anterior border with widely spaced, continuous row of straight setae ( Fig. 1 ), with 18–22 setae of varying lengths distributed along border of each pronotal half. Prosternal horn lacking, as in other Polycentropodidae .

Mesonotum and metanotum completely membranous, with purplish hue dorsally and whitish coloration laterally and ventrally. Meso- and metathoraces with one pair of short anterodorsal setae ( Fig. 7 ad), one pair of long posterodorsal setae ( Fig. 7 pd) and one short and one long pleural setae ( Fig. 7 pl). Foretrochantin ( Figs. 3 t , 8 t ) yellowish brown, elongate, digitiform and acute, fused with yellowish brown episternum ( Figs. 3 , 8 s ) without suture; with black pleural suture between episternum and epimeron ( Figs. 3 , 8 m ), the latter posteriorly elongated, acute and strongly bent ventrad ( Fig. 2 m ). Mid- and hind pleural sclerites ( Fig. 10 mp) much smaller, elongate triangular, with blackish ventral margins.

Legs yellow to yellowish brown, with numerous secondary setae on coxae, trochanters, and femora; tibiae and tarsi with smaller numbers of setae ( Fig. 8 ). Foretarsi each distinctly more than half as long as its tibia ( Fig. 8 , double arrow). Femora, especially mid- and hind femora, each with long ventral setal fringe. Each tibia with two long, black, slender apical spurs (e.g., Fig. 10 , arrows), foretibia with additional subapical spur (not visible in Fig. 8 ). Tip of each tarsus with ventral, semicircular fringe of tiny setae. Tarsal claws long and slender, slightly curved, pointed, each with basal spur ( Figs. 8–10 ).

Abdomen. Abdomen without gills, slightly flattened dorsoventrally (depressed), with purplish hue dorsally and whitish coloration laterally and ventrally. Abdominal segments I–VIII each with one pair of ventral ( Fig. 11 v ), two pairs of dorsal ( Fig. 11 ad, pd) and one pair of pleural setae ( Fig. 11 pl); in addition, abdominal segments II– VIII each with lateral longitudinal band of 25–35 short setae, creating ‘lateral fringe’ ( Fig. 11 , dotted oval). Last abdominal sternum (sternum IX) with 27–39 sternal setae; secondary setae usually much shorter than all 8 primary setae ( Fig. 12 op, ip, p). Abdominal dorsum IX without sclerite but with trio of setae on each side of body: one long primary seta ( Fig. 13 p ) and two tiny secondary posterolateral setae ( Fig. 13 is, os); outermost secondary seta ( Fig. 13 os) distinctly longer than median secondary seta ( Fig. 13 is).

Anal prolegs very prominent, incorporating section of abdominal segment IX, and consisting of unsclerotized basal ( Fig. 14 so) and sclerotized apical sections ( Fig. 14 sc) with 143–158 and 49–57 setae, respectively. Anal claw obtuse-angled, inner margin without teeth ( Fig. 14 ).

Figures

FIGURES 1–6. Plectrocnemia renetta Malicky 1975, 5th instar larva. 1, head and prothorax, dorsal (dotted lines = halftrapezoidal pattern of spots on posterior frontoclypeus, about 100°; small numerals refer to setal positions); 2, head and prosternum, ventral (a = anterior ventral apotome; ls – labial spinneret; ml = maxillary lobe; mp = maxillary palp; m = ventral process of epimeron; ss = submental sclerite; arrows = ventral processes of pronotum); 3, head and prothorax, right lateral (m = epimeron; s = episternum; t = foretrochantin); 4, labrum, dorsal (arrow = central pigmented mark); 5, mandibles, dorsal (a = apical tooth; arrows = subapical teeth); 6, mandibles, ventral (a = apical tooth; arrows = subapical teeth). Scale bars: 0.5 mm.

FIGURES 7–11. Plectrocnemia renetta Malicky 1975, 5th instar larva. 7, metathorax, right lateral (ad = anterodorsal seta (sa1); mp = metapleuron; pd = posterodorsal seta (sa2); pl = pleural seta (sa3)); 8, left foreleg, posterior (m = epimeron; s = episternum; t = foretrochantin; double arrow = projected half length of tibia); 9, right midleg, anterior; 10, right hind leg, anterior (mp = metapleuron; arrows = apical spurs on tibia); 11, abdominal segment V, right lateral (ad = anterodorsal seta (sa1); pd = posterodorsal seta (sa2); pl = pleural seta (sa3); v = ventral seta; dotted oval = lateral fringe). Scale bars: 0.5 mm.

FIGURES 12–17. Figures 12–14. Plectrocnemia renetta Malicky 1975, 5th instar larva: 12, abdominal segment IX, ventral (ip = innermost primary seta; op = outermost primary seta; p = intermediate primary setae); 13, abdominal segment IX, dorsal, posterolateral setal trio (is = inner secondary seta; os = outer secondary seta; p = primary seta); 14, left anal proleg, left lateral (sc = distal sclerotized section; so = proximal unsclerotized section; dotted lines = right angle superimposed on obtuse-angled anal claw). Figure 15. P. kingi McLachlan 1881, 5th instar larva, left foreleg, posterior (double arrow = projected half length of tibia). Figure 16. P. g. geniculata McLachlan 1871, 5th instar larva, abdominal segment IX, ventral (ip = innermost primary seta; op = outermost primary seta; p = intermediate primary setae). Figure 17. P. c. conspersa (Curtis 1834), 5th instar larva, abdominal segment IX, ventral (ip = innermost primary seta; op = outermost primary seta; p = intermediate primary setae). Scale bars: 0.5 mm.