Hydropsyche mostarensis, Klapalek, 1898

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 : 384

Hydropsyche mostarensis , 5th instar larva

( Figs. 8–14 )

Body length: Ranging from 15 to 17 mm (n = 6).

Head: Rectangular, about as long (mean length: 1.39 mm, S.D = 0.02, n = 6) as wide (mean width: 1.32 mm, S.D = 0.02, n = 6) ( Figs. 8, 9 ). Cephalic capsule ( Fig. 8, 9, 12 ) light brown to brown (chestnut). Frontoclypeal apotome ( Fig. 10 ) longer than wide (width of anterior edge similar to width of posterior third), ogival, anterior margin and anterior sides nearly straight to slightly concave, posterior sides rounded, posterior tip pointed. Lateral and aboral light spots always joined on each side, leaving dark and elongated patch with Y shape in middle of apotome ( Figs. 8, 9 ) and with aboral light spots forming V or Y figure in posterior half of frontoclypeus. Oral light spot usually absent ( Figs. 8, 9 ), sometimes present ( Fig. 10 ). In ventral view ( Fig. 11 ), two distinctive longitudinal, wide dark bands covering stridulatory files and most of cephalic capsule. Submentum ( Fig. 11 ) light brown or darker, with lateral lobes short and wide (length-width ratio: 0.21–0.24, Mean = 0.23, S.D. = 0.01, n = 6). Seta 9 of dorsal surface dark and longer than other setae of head; seta 1 long, dark and longer than other setae of anterior margin of frontoclypeus; seta 7 dark, slightly shorter than seta 9; seta 11 situated nearby on outer side thin, small, and dark; ventral seta 8 similar to seta 7; seta 10 small, pale, situated anterior to eye, shorter than setae 11 and 12; seta 14 long, dark, situated posteriorly to eye; setae 15 and 16 short, pale, spine-like, situated near suture. Secondary setae numerous, pale, short, and spine-like, dorsolateral on each side of head.

Thorax: Notal plates light brown ( Fig. 12 ). Metanotum lighter than pronotum and mesonotum. Pronotum and mesonotum of same colour as head or lighter. Median regions of posterior prosternites strongly pigmented, light brown (chestnut) and irregularly oblong ( Fig. 13 ). Lateral regions of prosternites lighter, almost invisible, may be separated from median regions by light areas ( Fig. 6 ). Ventral gills present on mesosternum and metasternum. Legs yellowish, light brown; setae mainly dark. Forelegs prehensile, slightly shorter but thicker than midlegs and hind legs. Anterior margin of each forecoxa with 7 thick, dark, short spine-like setae and long, dark, primary basal seta; several dark, short, spine-like setae at posterior margin; at external (posterior) surface, one long dark, thick, ventral seta reaching midlength of trochanter. Foretrochanters and forefemora on external (posterior) surfaces each with numerous long, slender, dark, setae on ventral margin, mixed with row of several dark and pale, median setae. Foretibiae longer than foretarsi, both with few short, pale, thick, spine-like setae on ventral margins and several long and median, pale, thick, spine-like setae on dorsal margins. Mid- and hind legs similar in siZe, shape, and structure; trochanters and femora of midlegs each with several median, pale and dark, spine-like setae on ventral margin and one dark, very long, slender seta; trochanters of hind legs with several median, pale, spine-like setae on ventral margin and two dark, long, slender setae; femora of hind legs each with several short, thick, pale, spine-like setae on ventral margin and long, slender, black seta. Tibiae and tarsi of mid- and hind legs each with short, 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 each of abdominal sterna I–VII. Pair of ventromesal gills with single-stemmed stalks on each of abdominal sterna II–VI. Pair of lateral (pleural) gills present on each of abdominal segments III–VII simple, finger-like. Pair of sternites VIII subtriangular, light brown–ochre; anterior parts of these sternites with tapered, short, thick setae; posterior borders of these sternites each with seven long, thick black bristles. Pair of sternites IX subtriangular, light brown–ochre; setae on anterior parts of these sternites with tapered, short, thick setae; posterior borders of these sternites with black bristles longer than those of segment VIII ( Fig. 14 ). 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, thick dark hair-like setae lacking prominent setal sockets. Ventral membranous areas covered with hair-like setae. Caudal lobes lacking setae ( Fig. 14 ).

Figures

FIGURES 8–14. Hydropsyche mostarensis Klapálek 1898, larva. 8, head, dark specimen, dorsal; 9, head, light specimen, dorsal; 10, frontoclypeal apotome, dorsal; 11, head & submentum, ventral; 12, head & pronotum, left lateral; 13, prosternites, ventral; 14, plates on abdominal sterna VIII and IX, ventral.Scale bars: Figs.8, 9, 10, 11, 13 & 14: 0.5 mm; Fig.12: 1.0 mm.

FIGURES1–7. Hydropsyche cetibeli Malicky & Sipahiler 1993, larva.1, habitus, right lateral; 2, head, dark specimen, dorsal; 3, head, light specimen, dorsal; 4, frontoclypeal apotome, dorsal; 5, head & submentum, ventral; 6, prosternites, ventral; 7, plates on abdominal sterna VIII and IX, ventral. L = lateral light spot; La = lateral aboral light spot; Lp = lateral section of posterior prosternites; M = median aboral light spot; Mp = median section of posterior prosternites; O = oral light spot; S = submentum. Scale bars: Fig. 1: 3.0 mm; Figs. 2, 3, 5 & 6: 0.75 mm;Fig.4: 0.5 mm; Fig.7: 1.0 mm.