Rhyacophila aphrodite Malicky 1975

Waringer, Johann & Malicky, Hans, 2019, Identification and morphology of a rhyacophilid caddisfly larva from Cyprus: Rhyacophila aphrodite Malicky 1975, Zootaxa 4623 (3), pp. 563-570 : 564

Description of the final instar larva of Rhyacophila aphrodite Malicky 1975

Biometry. Body length of final instar larva 18.2 to 22.0 mm, head width 1.24 to 1.34 mm (n = 2). Chaetotaxonomy according to Williams & Wiggins (1981) and Friedrich et al. (2015), anal proleg terminology following Nielsen (1942).

Head. Head capsule elongate, mean length: width ratio 1.33, lateral margins slightly convex with maximum width at height of posterior tip of frontoclypeal apotome ( Fig. 1 ); surface finely wrinkled. Base coloration yellow, with conspicuous reddish brown, oval muscle attachment spots on dorsal, ventral, and lateral sides of parietalia, on frontoclypeal apotome, and along coronal suture ( Figs. 1–3 ). Additional brown pigmentation on parietalia, dorsally from posterior frontoclypeal suture along posterior coronal suture to foramen occipitale, laterally from setae #12 and #14 to apophysis of foramen occipitale and ventrally, from foramen occipitale to center of parietalia ( Figs. 1–3 ). On each parietal, setae #7, #9, #12, #14, #15, and #16 long and conspicuous ( Fig. 1 ). Frontoclypeal apotome with deep central constriction, 5 pairs of primary setae, dark brown anterior margin, and U-shaped light brown pigmented area posterior of central constriction including 4–5 light muscle attachment spots ( Fig. 1 ). Antennae inconspicuous, close to anterior parietal border, with short flagellum (not visible in Fig. 1 ). Yellowish labrum with 6 pairs of primary setae ( Fig. 1 ). Ventral apotome ( Fig. 2 va) shaped like isosceles triangle, dark brown, with thickened anterior border ( Figs. 2 , 4 ). Sclerites of maxillolabium yellowish brown; lateral borders of cardines, stipites, and mentum dark brown to black ( Fig. 4 ). Mandibles medium brown, almost black apically, and asymmetrical ( Fig. 4 ): right mandible with short, stout basal tooth ( Fig. 4 bt), lacking on left mandible and replaced there by straight cutting edge ( Fig. 4 ce). Each mandible with apical tooth ( Fig. 4 at) and 2 lateral setae ( Fig. 4 , arrows).

Thorax. Pronotum fully covered by 2 large sclerites with their maximum widths at insertions of setae # 7 and 9; sclerites tapering anteriorly and posteriorly; lateral borders slightly concave ( Fig. 5 ). Pronotal sclerites yellowish, each with reddish brown muscle attachment spots over light brown pigmentation creating arrow-shaped pattern pointing mesad ( Fig. 5 ). In addition, oval concentrations of muscle attachment spots in posterolateral sections of sclerites, each with seta #5 near its anterior border. Additional muscles attachment spots and narrow stripes of pigment bordering posterior half of median suture ( Fig. 5 ). Posterior margin thick and black, with pair of semicircular posterior submesal bulges each with yellow center ( Fig. 5 pm) and posterolateral prolongations ( Fig. 3 pp). Posterolateral border of pronotal sclerites with black stripe fading laterally, absent anterior of insertion of seta #9; with thin black stripe above insertions of setae #9 and #7 ( Fig. 3 ). Pronotal notch at anterolateral corner semicircular, with 2 long setae ( Figs. 3 and 5 , #22, #23) and 3 tiny setae ( Fig. 5 , dotted oval). Prosternal horn lacking, prosternite ill-defined, quadrangular, yellowish white ( Fig. 2 p ). Meso- and metathoraces totally unsclerotized, with pale purplish-blue coloured areas subdivided by whitish longitudinal and transversal stripes; each with single pair of anterior (setal area 1 = sa 1) setae and pair of groups of one long and two tiny posterior (setal area 2 = sa 2) setae.

Procoxae each with triangular conical basal process ( Fig. 3 bp) touching ventral extension of black pleural suture ( Fig. 3 ps). Dorsal apex of pleural suture close to posterolateral prolongations of pronotum ( Fig. 3 pp). Proepisternum small, quadrangular, yellowish brown; pro-epimeron very narrow, creating yellowish ventral plate below pleural suture ( Fig. 3 em). Protrochantin triangular, yellow, with dark posterior tip and dark dorsal and ventral borders ( Fig. 3 tr); its anterior process finger-shaped, bearing seta #10 ( Fig. 6 ). Episterna and epimera of meso- and metathoraces almost completely reduced to black vertical pleural sutures ( Fig. 9 ps), fused with horizontal trochantin bearing seta #10 ( Lepneva 1964; seta #10 hidden by thoracic gill in Fig. 9 ). Legs yellowish brown, with forefemora distinctly wider than mid- and hind femora, and sclerite borders dark brown to black ( Figs. 6–9 ). Counts of long setae on each leg as follows: coxa 5 (#1, #3, #4, #5, #6; Figs. 6 , 9 ), trochanter 5 (#3–#6 visible in anterior view), femur 6 (#1, #2, #5, and #6 visible in anterior view), tibia 6 (#3–#6 and one secondary seta visible in anterior view), tarsus 4 (#1–#4; Fig. 6 ). Tarsal claws sickle-shaped, pointed (in Fig. 6 , tarsal claw heavily worn), with basal spur originating from conical base ( Figs. 6–8 ).

Abdomen. Abdomen slightly depressed (flattened dorsoventrally), with purplish–blue dorsal colouration subdivided by whitish lines. Laterally and ventrally pale cream coloured. Each segment with 2 pairs of long dorsal primary setae ( Fig. 10 , setae #2, #5), one pair of tetrafilament lateral gills ( Fig. 10 ), and pair of ventral setae #10 ( Fig. 11 ). Lateral fringe lacking.

Abdominal dorsum IX covered by large, yellow quadrangular sclerite with black anterior and posterior borders and dark brown markings and pair of lateral black projections; setae #2 and #3 inserted on sclerite, seta #4 on posterior edge and seta #5 inserted on small isolated posterolateral sclerite ( Figs. 11, 12 ). With tufted, white anal gills ( Figs. 11, 12 ag). Anal proleg sclerites yellowish brown, with dark brown borders and dark brown suture between anterior and posterior parts of proximal sclerite ’b’ ( Fig. 11 ). Each proleg having proximal sclerite ’b’ ( Fig. 11 pb) with oblique dark bar of suture extending onto strong basoventral hook ( Fig. 11 h ) anteriorly and with long terminal sword process ( Fig. 11 sp) posteriorly; distal sclerite ’b’ with dorsal hornlike process with blunt tip ( Fig. 11 bd). Ventral sclerite ‘c’ nearly round ( Fig. 11 c ). Ventral sclerite ( Fig. 11 bv) with short median seta. Anal claw (ac) partially divided by ventral membrane into proximal and distal sections, latter fitted with two short basoventral teeth ( Fig. 11 , arrow). Anal claw teeth perpendicular to longitudinal axis of anal claw; distal anal claw tooth shorter than half anal claw width at distal tooth insertion ( Fig. 11 arrow).

Figures

FIGURES 1–3. Rhyacophila aphrodite Malicky 1975, 5th instar larva. 1, head, dorsal (lb = labrum; small numbers refer to setal positions); 2, head, ventral (p = prosternite; va = ventral apotome; small numbers refer to setal positions); 3, head and prothorax, right lateral (bp = basal process of coxa; em = epimeron; es = episternum; pp = posterolateral prolongation; pr = pronotal sclerite; ps = pleural suture; tr = trochantin; small numbers refer to setal positions). Scale bars: 0.5 mm.

FIGURES 4–8. Rhyacophila aphrodite Malicky 1975, 5th instar larva. 4, mandibles and maxillolabium, ventral (at = apical tooth; bt = basal tooth; c = cardo; ce = cutting edge; g = galea; lb = labrum; lm = left mandible; lp = labial palp; mp = maxillary palp; m = mentum; o = orifice of silk gland; pf = palpifer; pg = palpiger; rm = right mandible; s = stipes; sm = submentum; va = ventral apotome; arrows = pair of mandibular basal setae); 5, prothorax, dorsal (pm = posterior submesal bulge; dotted oval = tiny setae of pronotal notch; small numbers refer to setal positions); 6, right foreleg, anterior (small numbers refer to setal positions); 7, right mesothoracic gill and midleg, anterior; 8, right metathoracic gill and hind leg, anterior. Scale bars: 0.5 mm.

FIGURES 9–12. Rhyacophila aphrodite Malicky 1975, 5th instar larva. 9, detail of mesothoracic gill, left lateral (ps = pleural suture; tg = thoracic gill; tr = trochantin; small numbers refer to setal positions); 10, abdominal segments II and III, right lateral (small numbers refer to setal positions); 11, abdominal segments IX, X, and anal proleg, right lateral (ac = anal claw; ag = anal gills; bd = distal ‘b’ sclerite; pb = proximal sclerite ‘b’; bv = ventral ‘b’ sclerite; c = sclerite ‘c’; h = basoventral hook anteriorly on proximal sclerite ‘b’; sp = sword process posteriorly on proximal sclerite ‘b’; small numbers refer to setal positions; arrow = teeth on anal claw); 12, abdominal segments IX, X, and anal proleg, dorsal (ag = anal gills; small numbers refer to setal po- sitions). Scale bars: 0.5 mm.