Hydropsyche cerva Li & Tian 1990

Ge, Xinyu, Wang, Yinchang, Wang, Beixin & Sun, Changhai, 2020, Descriptions of larvae of three species of Hydropsyche Pictet 1834 (Trichoptera Hydropsychidae) from China, Zootaxa 4858 (3), pp. 358-374 : 359-363

Hydropsyche cerva Li & Tian 1990

General Description. Larvae (5th instar). Body length 10–13 mm (n = 5). Body grayish white in alcohol. Head and pronotum dark brown, legs and anal claws yellowish brown.

Head. Head ( Fig. 2A ) capsule subquadrate, nearly square, 1.3 mm long, 1.1 mm wide in dorsal view. Dorsum of head uniformly black or very dark brown, except for small yellowish areas around eyes and posterolaterally, otherwise without conspicuous light marks or stripes. Frontoclypeal apotome with anterior margin slightly convex; with conspicuous transversal crease at midlength; and with posterior angle ogival, at about 70° angle. Posterior portion of each frontoclypeal suture nearly straight. In lateral view ( Fig. 2B ), eyes oval, black. Head with posterolateral regions yellowish. In ventral view ( Fig. 2C ), anterior ventral apotome (avp) nearly triangular, brown, with anterior border slightly concave and anterolateral angles rounded. Ventral ecdysial line more than twice as long as anterior ventral apotome. Posterior ventral apotome tiny, triangular, dark brown. Dorsum of head with brown hair-like setae, short yellowish-brown truncate peg-like setae, and short acuminate peg-like setae. Labrum dark brown, with its anterior margin convex and each anterior lateral margin with hair- like setae. Mandibles ( Fig. 2D ) brown, triangular in dorsal view, left mandible with apical tooth and four subapicomesal teeth; with about eight setae at lateral margin and with brush of about dozen stiff hairs at middle of inner side. Right mandible with apical tooth and four subapical teeth and with about ten setae at lateral margin. Submentum ( Fig. 2E ) in ventral view with basal 2/3 somewhat trapezoidal and distal 1/3 divided, forming two lobes; posterior margin slightly convex posteriorly; each anterolateral corner with some long, strong setae and many short setae. Maxilla ( Fig. 2E ) each with cardo drop-shaped, brown; stipes ( Fig. 2F ) with three clusters of setae, each stipes with about seven setae on membranous portion, five setae and six setae in lateral and medial clusters, respectively, on triangular ossification of stipes. Each maxillary palp 5-segmented, tapering from base to apex, galea adjacent to medial margin of palp. Labium ( Fig. 2F ) triangular and short with notched brown mentum in ventral view.

Thorax. Pronotum ( Fig. 3A ) subrectangular and dark brown in dorsal view, pronotum subdivided longitudinally by mesal suture, posterior margin nearly black, especially submesally. Pronotum covered with brown acuminate peg-like setae; short and transparent truncate peg-like setae, and slender, short, black hair-like setae. Prosternal plate ( Fig. 3B , ppl) nearly trapezoidal, width about five times length; anterior margin blackish, slightly sinuous, slightly convex anteriorly on meson, posterior margin slightly concave. Intersegmental fold often covering two pairs of sclerites ( Fig. 3B , lpi, mpi) posterior of prosternal plate; on each side lateral sclerite piece (lpi) and submesal sclerite piece (mpi) behind posterior prosternal sclerite fused into subrhombic sclerite ( Fig. 3B ), lateral sclerite irregularly notched posterolaterally.

Mesonotum ( Fig. 3C ) brown in dorsal view, undivided on midline, anterolateral angles lateral margins and posterolateral angles with black borders; posterior margin with black convex arc-shaped mark at middle; pair of posterolateral regions without dark marks. Diagonal grooves scarcely discernible. Muscle scars darker than background. Sparse truncate peg-like setae scattered over whole surface of notum, anterior margin with many hair-like setae and few truncate or acuminate peg-like setae.

Metanotum ( Fig. 3D ) of same color as mesonotum and undivided on midline; posterior margin shallowly concave, with mesal black transverse mark. Broad and deep diagonal groove issuing from each anterolateral angle, extending 2/3 distance toward posterior meson of notum. Muscle scars darker than background, longitudinally arranged. Setae on metanotum and mesonotum less dense than on pronotum. Mesosternum and metasternum with one and two pairs of single-stemmed gill, respectively.

Legs. Legs ( Figs 4A, 4C, 4D ) yellowish brown. Forelegs slightly shorter and thicker in structure and darker in color than mid- and hind legs. Each foretrochantin bifurcate ( Fig. 4B ), two branches divergent at angle of about 70º, with about eight setae, upper branch slender, lower one stout. Forecoxae shorter than mid- and hind coxae and somewhat conical in lateral view, each having dorsal margin with 7–10 spike-like setae. Trochanters ( Fig. 4A ) each two-segmented and approximate triangular, each with basal segment subtriangular and shorter than subtriangular apical segment, trochanteral brush usually present on apical segment, ventral margin with more than 15 spike-like setae and two long-slender setae. Forefemora in lateral view pentagonal, with dorsal margin (scraper) protruding at midlength, dorsal and ventral margins with dense long-slender setae and spike-like setae, respectively. Foretibiae and foretarsi shorter and stouter than mid- and hind tibiae and tarsi. Tarsal claws of forelegs slightly curved downwards, each with basal seta small. Mid- and hind coxae cylindrical, with dense spike-like setae. Trochanters each two-segmented and approximately triangular, with dense spike-like setae and some long-slender setae. Mid- and hind femora cylindrical, with few long-slender setae and several shorter spike-like setae. Tarsal claws short, slightly curved downwards subapically, each with basal seta stout.

Abdomen. Abdominal segments I–IX covered with dense black hair-like setae and sparsely scattered, halferect scale-hair setae ( Fig. 4E , sh). Segment I with two pairs of bifid-stemmed gills; segments II–VI each with pair of ventrolateral bifid-stemmed gills and pair of ventromesal single-stemmed gills; segments III–VI with pupal gill buds laterally; segment VII with pair of bifid-stemmed gills. Subtriangular sterna of segments VIII and IX each with pair of ventral plates ( Fig. 4F , vs), these sternites yellowish brown, covered with tapered, short acuminate peg-like setae, posterior borders of these sternites with some black long slender setae. Anal prolegs ( Fig. 4G ) each slightly sclerotized with spike-like setae and apical part with about 30 long slender setae arranged in one plane similar to spines of Chinese fan. Anal claws ( Fig. 4G ) yellowish brown, hook-like, angled about 90º.

Diagnosis. The larva of H. cerva is similar to that of H. grahami Banks 1940 , (morphotype c1 of Zhou, 2007), but differs from it by the head capsule with posterolateral corners of parietals pale brown, not black to brown. It is also similar to the larva of H. orientalis Martynov 1934 , but can be distinguished from the latter by the anterior margin of frontoclypeal apotome slightly concave, not straight.

Material examined. Three larvae and three males, CHINA, Yun-nan Province , Qiao-jia County, Xiao-niulan cun, Xiao-niu-lan-jiang, 27°38’90”N, 103°10’39”E, Alt. 612 m, 18 Aug 2019, collected by Chang-hai Sun & Yin-chang Wang ; two larvae, Qiao-jia County, Yi-li-he, 27°78’73’’N, 103°02’45”E, Alt. 738 m, 17 Aug 2019, collected by Chang-hai Sun & Xin-yu Ge ; two larvae, Yong-ren County, Wan-bi-cun, Yu-pao-jiang, 26°34’05”N, 101°19’78”E, Alt. 1128 m, 17 Aug 2019, collected by Bei-xin Wang & Xin-yu Ge; one larva, Yuan-mou County, Jiang-bian-cun, Long-chuan-jiang, 25°85’15”N, 101°87’08”E, Alt. 967 m, 16 Aug. 2019, collected by Bei-xin Wang & Yin-chang Wang; one larva, Si-cuan Province, Jin-yang County, Lu-gao Town, Jin sha jiang, 27°55’31”N, 103°19’61”E, Alt. 588 m, 18 Aug 2019, collected by Chang-hai Sun & Xin-yu Ge ; one larva and three males, Ningnan County, Hu-lu-kou town, Hei shui he, 26°96’56”N, 102°87’63”E, Alt. 610 m, 17 Aug 2019 , collected by Chang- hai Sun & Xin-yu Ge; 2 larvae, Jin-yang County, Dui-ping Town , Shan-jiang-cun, 27°25’47”N, 102°95’67”E, Alt. 750 m, 18 Aug 2019, collected by Chang-hai Sun & Xin-yu Ge.

Notes. The larvae of H. cerva were collected in tributaries of Jinsha River basin, they were found in both clean and polluted habitats. The substrate consists of silt, pebbles, cobble and boulders. Altitude distribution between 588–1128 m. Water velocity relatively low.

Figures

FIGURE 2. Head of Hydropsyche cerva Li & Tian 1990. 2A, dorsal; 2B, right lateral; 2C, ventral; 2D, left mandible, dorsal; 2E, submentum, cardo, and anterior ventral apotome, ventral; 2F, maxillae and labium, ventral. avp = anterior ventral apotome; car = cardo; lab = labrum; labi = labium; mpa = maxillary palp; pva = posterior ventral apotome; sub = submentum; vel = ventral ecdysial line. Scale bars: 0.1 mm.

FIGURE 3. Thorax of Hydropsyche cerva Li & Tian 1990. 3A, pronotum, dorsal; 3B, prosternal plates and posterior prosternal sclerites, ventral; 3C, mesonotum, dorsal; 3D, metanotum, dorsal; lpi. = lateral piece; mpi. = median piece; ppl. = prosternal plate. Scale bars: 0.1 mm.

FIGURE 4. Legs and abdomen of Hydropsyche cerva Li & Tian 1990. 4A, right foreleg, right lateral; 4B, right propleuron, right lateral; 4C, right midleg, right lateral; 4D, right hind leg, right lateral; 4E, setae of abdominal tergum VII, left dorsolateral; 4F, sclerotized plates on abdominal sterna VIII and IX, ventral; 4G, left anal proleg, left lateral. apr = anal proleg; ls = long-slender setae; sh = scale-hair setae; sl = spike-like setae; vs = ventral sclerites. Scale bars: 0.1 mm.