Hydropsyche pygmalion, Malicky, 2001

Karaouzas, Ioannis, 2018, The larvae of three Greek species of Hydropsyche (Trichoptera: Hydropsychidae) and key for larvae of known Aegean Hydropsyche species, Zootaxa 4382 (2), pp. 381-392 : 386

Hydropsyche pygmalion , 5th instar larva

( Figs. 15–21 )

Body length: Ranging from 16 to 20 mm (n = 8).

Head: Head in dorsal view ( Figs. 15 & 16 ) rectangular, slightly longer (length: 1.7–1.8 mm, mean = 1.75 mm, n = 8) than wide (width: 1.6–1.7 mm, mean = 1.69 mm, n = 8). Cephalic capsule ( Figs. 15, 16 ) brown to dark brown. Frontoclypeal apotome ( Fig. 17 ) longer than wide, ogival, anterior margin and anterior sides straight or slightly concave, with posterior sides rounded, posterior tip almost pointed. Oral light spot absent ( Fig. 15 ) or faint ( Figs. 16, 17 ). Lateral and aboral light spots clearly visible and most noticeable. Anteromedian lobes of aboral light spots not joined with lateral ones, separated on each side by thin transverse stripe in middle, bordered posteriorly and anteriorly by light lyrate marking. In ventral view ( Fig. 18 ), pair of distinctive longitudinal, wide, dark bands usually covering stridulatory files and most of cephalic capsule except area behind submentum. In lightly-coloured specimens, longitudinal bands lighter and not covering most of cephalic capsule. Submentum ( Fig. 18 ) brown, with lateral lobes short and wide (width-length ratio: 0.21–0.23, mean = 0.22, S.D. = 0.01, n = 6). Seta 9 of dorsal surface dark, slender, longer than other setae of head; seta 1 long, dark and longer than other setae of anterior margin of frontoclypeus; seta 7 dark, situated near anterior margin, slightly shorter and thinner than seta 9; seta 11 situated nearby on outer side thin, small, and dark; ventral seta 8 similar to seta 7; seta 10 small, situated anterior to eye; seta 14 long, dark, situated posteriorly to eye; setae 15 and 16 short, situated near suture. Secondary setae numerous, short and spine-like, dorsolateral on each side of head.

Thorax: Notal plates brown to dark brown; pro- and mesonota same colour as head; metanotum slightly lighter than pronotum and mesonotum ( Fig. 19 ). Median regions of posterior prosternites strongly pigmented, dark brown, irregular, and transversely oblong ( Fig. 20 ). Lateral regions of posterior prosternites lighter, separated from median regions by light areas ( Fig. 20 ). Ventral gills present on meso- and metasterna. Legs brown, setae mainly black. Forelegs prehensile, slightly shorter but thicker than midlegs and hind legs. Anterior margin of each forecoxa with 1 long, slender, black, spine-like seta and few very short black and pale spine-like setae; ventral surface covered densely with many pale, thin setae; at external (posterior) surface, one long, dark, slender, ventral seta, reaching midlength of trochanter. Foretrochanters on external (posterior) surfaces, each with 3 long, dark, slender setae on ventral margin, mixed with row of several pale, median, slender setae. Forefemora each with numerous dark, median, slender setae on ventral margin, mixed with row of several short and median pale, spine-like setae. Foretibiae longer than foretarsi, both with few very short, pale, thick, spine-like setae on ventral margins and several long, pale, thick, spine-like setae on dorsal margins. Mid- and hind legs similar in siZe, shape, and structure. Trochanters and femora of midleg, each with several median, pale and dark, spine-like setae on ventral margin and one dark, very long, slender seta; trochanters of hind legs each with several median, pale, spine-like setae and one long and one very long dark, slender, spine-like setae ventrally; femora of hind legs each with several median, pale, spine-like setae on ventral margin and two long slender almost equal-length setae on ventral margin. Tibiae and tarsi of mid- and hind legs, each with short and median, pale, spine-like setae and 1 dark, long, slender seta on apicodorsal margin of tarsus.

Abdomen: Abdominal gills present on segment VII. Abdominal sterna with two types of gills: single-stemmed gills and bifid-stemmed gills. Pair of ventrolateral gills with bifid stalks on abdominal sterna I–VII. Pair of ventromesal gills with single-stemmed stalks on abdominal sterna II–VI. Pair of lateral (pleural) gills on each of abdominal segments III–VII simple, finger-like. Pair of sternites VIII subtriangular, dark reddish brown, with tapered, short, thick spike-like setae emanating from prominent sockets; posterior borders of these sternites each with more than 10 long, thick black bristles. Pair of sternites IX subtriangular, reddish brown; setae on posterior parts of these sternites almost as long and thick as those of segment VIII; posterior borders of these sternites with long, thick, black bristles ( Fig. 21 ). Anal prolegs each with bent claw and cluster of tapered, dark, long slender setae. Ventral side of each anal proleg bearing series of tapered, long, dark, hair-like setae lacking prominent setal sockets. Ventral membranous areas covered with hair-like setae and few long dark bristle-like hair ( Fig. 21 ).

Figures

FIGURES 15–21. Hydropsyche pygmalion Malicky 2001, larva. 15, head, dark specimen, dorsal; 16, head, light specimen, dorsal; 17, frontoclypeal apotome, dorsal; 18, head & submentum, ventral; 19, head, pro-, meso-, and metathoraces, right lateral; 20, prosternites, ventral; 21, plates on abdominal sterna VIII and IX, ventral. Scale bars: Figs. 15, 16 & 18: 0.75 mm; Figs. 17, 20: 0.5 mm; Fig. 19: 2.0 mm.