Rhyacophila palmeni McLachlan 1879

Karaouzas, Ioannis, Ibrahimi, Halil & Waringer, Johann, 2018, The larva of Rhyacophila palmeni McLachlan 1879 (Trichoptera: Rhyacophilidae) from Greece and Kosovo with notes on ecology and zoogeography including a key to the known Greek Rhyacophila larvae, Zootaxa 4514 (1), pp. 97-106 : 98-102

Description of the fifth instar larva of Rhyacophila palmeni McLachlan 1879

Biometry. Body length ranging from 16.4 to 17.5 mm, head width from 1.08 to 1.39 mm (n = 13). Soft body parts (mesonotum, metanotum, and abdomen) of live specimens green dorsally, pale green ventrally. Specimens in alcohol, purplish-green or purplish brown dorsally; lightly coloured ventrally. Sclerotised areas (head, pronotum, legs, abdominal dorsum IX and anal prolegs) light brown or yellowish with dark brown or black markings ( Figures 1–17 ).

Head. Head capsule elongated, yellowish brown, with lateral margins almost parallel, slightly convergent anteriorly, with slight constriction at eyes ( Figs. 1–8 ). Broad, transverse brown or light brown band across posterior 1/3 of frontoclypeus and adjacent sides of head interrupted by thin pale lines along frontoclypeal sutures, broad pale areas along coronal suture, and pale areas surrounding primary setae, especially setae 15 and 16 ( Figs. 1–6 , 9 ). Conspicuous brown muscle attachment spots at dorsal and lateral sides of parietalia, and along coronal suture ( Figs. 1–6 , 9 ). Dark brown marking at aboral end of frontoclypeus forming spade- or heart-shaped with crescentic row of four characteristic light muscle attachment spots ( Figs. 1–6 , often inconspicuous). Anterior edge of frontoclypeus (anteclypeus) almost straight, margined by light brown. Ventral view pale yellow except pale brown anterior and posterior margins, without any spots ( Figs. 7–8 ). Ventral apotome triangular, light brown or yellowish, merged with rectangular submentum ( Figs. 7–8 sm). Mouthparts ( Figs 4 m , 8 ) and labrum ( Figs 1–3 lb) typical of the genus.

Thorax. Pronotum trapezoidal, covered by two large sclerites tapering posteriorly, wider than head capsule ( Fig. 10 ). Yellowish and usually with few darker attachment spots in anterior half; posterior half mostly covered by transverse brown band bearing group of dark attachment spots, not always visible ( Figs. 6 , 10 tb). Posterior and lateral margins thickened and darkly striped, including anterolateral corners ( Figs. 9, 10 ). Legs pale brown, with numerous setae on coxae, trochanters, and femora; tibiae and tarsi brownish with few smaller and thinner setae ( Figs. 11–14 ). Forelegs shorter and stronger than mid- and hind legs. Forefemora distinctly wider than mid- and hind femora. Tarsal claws long and slender, curved, pointed, each with basal spur ( Figs. 11, 12, 14 ). Thoracic gills with slender, long filaments arising laterally from two basal branches above each coxa, characteristic for the Rhyacophila s. str. Group ( Figs. 12–14 ).

Abdomen. Abdomen slightly flattened dorsoventrally ( Fig. 16 ); most specimens in alcohol pale brown to yellowish-green ventrally and darker purplish-brown to purplish-green dorsally. Tufted gill filaments present on each side of segments I to VIII each arising from common base ( Figs. 15, 16 ). As in all species of Rhyacophila s. str., tracheal gills each consisting of short, thick ventral branch (vb) with numerous filaments near apex, and longer, more-slender dorsal branch (db) with numerous filaments on its dorsal side ( Figs. 15, 16 ). Dorsal sclerite on segment IX ( Fig. 17 ) trapezoidal and light brown in colour, with a darker posterior margin. Setae at posterior end long and black ( Fig. 17 ). Anal appendages each with proximal sclerite ( Fig. 18 b ) with ventral basal hook ( Fig. 18 h ) and with long lateral sword process ( Figs 17, 18 sp), extending beyond suture line but shorter than anal claw; anal claws each with three ventral teeth ( Fig. 18 ac).

Figures

FIGURES 1–4. Rhyacophila palmeni McLachlan 1879, 5th instar larval head, dorsal. 1–3, Specimens from Kosovo (bb = brown band on parietalia; bm = brown markings on frontoclypeus; f = frontoclypeus; lb = labrum; pa = parietale). 4, specimen from Kastori, Greece (m = mandibles). Scale bars: 0.5 mm.

FIGURES 5–8. Rhyacophila palmeni McLachlan 1879. 5, Head, dorsal, 5 th instar larva from Stropones, Greece. 6, Head and pronotum, dorsal, 5 th instar larva from Karpenisi, Greece (pn = pronotum; tb = transverse band). 7, Head, pro– and mesosterna, ventral, prepupa from Stropones, Greece (sm = submentum). 8, Head, ventral, 5 th instar larva from Kosovo (sm = submentum). Scale bars: 0.5 mm.

FIGURES 9–14. Rhyacophila palmeni McLachlan 1879, 5th instar larva. 9, Head and prothorax, right lateral, specimen from Kastori, Greece (pn = pronotum; pt = protrochantin). 10, Pronotum, dorsal, specimen from Kosovo (pn = pronotum; tb = transverse band). 11–14, specimen from Kosovo, right legs: 11, Foreleg, anterior (c = coxa; tr = trochanter; f = femur; ti = tibia; ta = tarsus; tc = tarsal claw; ts = tarsal spur); 12, midleg, anterior; 13, detail of midleg, dorsal (db = dorsal branch of pleural gill, vb = ventral branch of pleural gill); 14, hind leg, anterior. Scale bars: 0.5 mm.

FIGURES 15–18. Rhyacophila palmeni McLachlan 1879, 5th instar larva. 15, Gill of abdominal segment I, right lateral, specimen from Kosovo (db = dorsal branch, vb = ventral branch). 16, Abdominal sterna II–IV, ventral, specimen form Kosovo. 17, Abdominal tergum IX and anal prolegs, dorsal, specimen from Karpenisi, Greece (sp = sword process). 18, Abdominal segment IX and anal prolegs, right lateral, specimen from Kosovo (ac = anal claw; b = ‘b’ sclerite; c = ‘c’ sclerite; h = proximal hook of sclerite ‘b’; sp = sword process; arrows = teeth on anal claw). Scale bars: 0.5 mm.