Mean length of 5^th instar larvae is about 15 mm (n = 5). Overall body length is similar to most hydropsychid larvae (Fig. 1). The colours of the specimens in alcohol are as follows: body creamy-white; head features a mottled pattern of dark brown and yellowish-brown; pronotum, ventral prosternum, abdominal sternum, legs and anal claws yellowish-brown.

Figure 1.  

The overall body shape of larva of H. briareus in lateral view.

Head. The head is rectangular in dorsal view, about 1.9 mm long and 1.7 mm wide (Fig. 2A). Dorsum of head uniformly brown and yellowish-brown. Brown is primarily concentrated in the frontoclypeal apotome and both sides of the parietal bone, while there is a yellowish-brown area around the eyes and the posterior margin of parietal. In dorsal view, two yellowish marks are distributed on the frontoclypeal apotome, both presented in a circular shape. The pattern near the anterior margin is larger, shield-shaped, while the pattern near the coronal suture of the head is significantly smaller. Anterior margin of frontoclypeal apotome is nearly straight. Frontoclypeal apotome with posterior angle ogival, at an angle of about 100°. Head in lateral view is nearly trapezoid, with posterolateral regions yellowish, mandible triangular and margin dark brown, eyes oval and black (Fig. 2B). In ventral view, anterior ventral apotome nearly triangular, with anterior border slightly concave and anterolateral angles rounded (Fig. 2C). Ventral ecdysial line nearly twice as long as anterior ventral apotome. Posterior ventral apotome tiny, triangular, brown. Many acuminate peg-like setae and truncate peg-hair setae distributed throughout the dorsum of head, while many long-slender setae only distributed on the front half part of the head. Mandibles dark brown (Fig. 2D), triangular in dorsal view. Left mandible with about five setae at lateral margin and with brush of about a dozen stiff hairs at middle of inner side, with apical tooth and four subapicomesal teeth. Submentum (Fig. 2E) in ventral view brown, with basal 2/3 somewhat trapezoidal and distal 1/3 divided, forming two lobes, lobes nearly square. Submentum posterior margin slightly convex posteriorly, each anterolateral corner with some few stout long setae and many short setae.

Figure 2.  

Head of H. briareus. A dorsal; B, right lateral; C, ventral; D, left mandible, dorsal; E, submentum, cardo and anterior ventral apotome, ventral. Abbreviations: avp. anterior ventral apotome; car. cardo; lab. labrum; pva. posterior ventral apotome; sub. submentum; vel. ventral ecdysial line.

Thorax. Pronotum (Fig. 3A) subrectangular and yellowish-brown in dorsal view, pronotum subdivided longitudinally by mid-dorsal ecdysial line, both sides are shaped nearly like squares and covered with many short acuminate peg-like setae, hair-like setae and few truncate peg-hair setae. Anterior margin of pronotum straight on both sides of mid-dorsal ecdysial line and colour is darker than the middle; posterior margin shows a circular arc shape in dark brown on both sides of mid-dorsal ecdysial line, concave inward at mid-dorsal ecdysial line, concave-shaped rectangular. Prosternal plate (Fig. 3B) trapezoidal, with width about 4 times its length, slight protrusions on the left and right quarter; anterior margin sinuous, protruding outwards in the middle, the colour is dark on the sides and light in the middle. Posterior margin slightly concave inwards, the dark area in the middle is rectangular. Lateral piece and median piece behind each end of posterior prosternal sclerite fused into rhombic piece on each side, each with anterolateral and posteromesal corners acute, with width about 3.5 times its length. Mesonotum (Fig. 3C) subrectangular and lightly yellowish-brown in dorsal view, covered with dark hair-like setae and truncate peg-hair setae, one long setae at positions sa2. Anterior margin approaching a straight line in brown; posterior margin mark black, concave slightly inward and U-shaped in the middle. Metanotum (Fig. 3D) subrectangular lightly yellowish and length less than mesonotum and pronotum in dorsal view, Broad and deep diagonal groove issuing from each anterolateral angle extending 2/3 distance towards posterior meson of notum. Muscle scars darker than background, longitudinally arranged. Anterior margin of metanotum similar to those of mesonotum; posterior margin shallowly concave, with mesal black quadrate mark. Setae on metanotum and mesonotum less dense than on pronotum. Mesosternum and metasternum with one and two pairs of single-stemmed gill, respectively.

Figure 3.  

Thorax of H. briareus. A pronotum, dorsal; B prosternal plates and posterior prosternal sclerites, ventral; C mesonotum, dorsal; D metanotum, dorsal. Abbreviations: lpi. lateral piece; mpi. median piece; ppl. prosternal plate.

Legs. Legs yellowish-brown. Forelegs slightly shorter and thicker than mid- and hind legs (Fig. 4A, 4C and 4D). Each fore-trochantin short and thick bifurcated, upper branch slender, lower one stout, two branches divergent at angle of about 90º, with about 8 setae. Fore coxae shorter and thicker than mid- and hind coxae and shaped conical; mid- and hind coxae are relatively long and shaped cylindrical. Trochanters each two-segmented and approximately triangular, each with basal segment subtriangular and shorter than subtriangular apical segment, ventral margin with more than 15 spike-like setae and two long-slender setae. Fore femora in lateral view pentagonal, each with dorsal margin protruding at mid-length; ventral and dorsal margins with dense long-slender setae and spike-like setae, respectively. Fore tibiae and fore-tarsi tube-like stouter than mid- and hind tibiae and tarsi. Trochanters each two-segmented and approximate triangular with dense spike-like setae and some long slender setae. Mid- and hind femora cylindrical. Tarsal claws of fore-, mid- and hind legs each slightly curved downwards apically.

Figure 4.  

Legs and abdomen of H. briareus. A left foreleg, left lateral; B left propleuron, left lateral; C left mid-leg, left lateral; D left hind leg, left lateral; E setae of abdominal tergum VI, left dorsolateral; F plates on abdominal sterna VIII and IX, ventral; G anal prolegs, left lateral. Abbreviations: apr. anal proleg; ls. long slender setae; sh. scale-hair setae; sl. spike-like setae; vs. ventral sclerites.

Abdomen. Abdominal sterna with three types of gills: bifid-stemmed gill, single-stemmed gill and pupal gill. Segment I ventrally with two pairs of bifid-stemmed gill, segments II–VI each with ventrolateral bifid-stemmed gill and ventromesal single-stemmed gill, segments III–VI with pupal gill buds laterally, segment VII with pair of bifid-stemmed gills. Abdominal segments I–IX covered densely with black hair-like setae and sparsely with half-erect scale-hair setae (Fig. 4E). There is one long slender seta at each of the sa2 of the abdominal segments I–VII. Subtriangular sterna of segments VIII and IX each with pair of ventral plates (Fig. 4F), yellowish-brown, covered with tapered, short acuminate brown peg-like setae, posterior margin of these sternites with long, black spike-like setae. Anal prolegs and claws yellowish-brown. Anal prolegs (Fig. 4G), each slightly sclerotised with spike-like setae and apical part with about 25 long slender setae arranged in one plane. Anal claws (Fig. 4G) hook-like, angled about 60º.

The larva of H. briareus is very similar to the larva of H. serpentina Schmid, 1965 in the cephalic colour patterns and the overall shape in dorsal view, but differs from it in the following characteristics: (1) the posterior margin of metanotum has a mesal black punctate mark; (2) frontoclypeal apotome has two yellowish-brown stripes, the anterior margin is larger, shield-shaped; (3) the anterior margin of the frontoclypeal apotome is slightly concave; (4) the posterior angle of frontoclypeal apotome is ogival, at an angle of about 100°, with posterior portion of each frontoclypeal suture slightly sinuous.

Mean length of 5^th instar larvae about 21 mm (n = 5). Overall body shape as usual in hydropsychid larvae (Fig. 5). The colours of the specimens in alcohol are as follows: body creamy-white; head dark brown with yellow stripe; pronotum, ventral prosternum, abdominal sternum, legs and anal claws yellowish-brown.

Figure 5.  

The overall body shape of larval H. kozhantschikovi in lateral view.

Head. Head at dorsal view roughly rectangular, about 2.7 mm long and 2.4 mm wide. Dorsum of head mostly light brown, with yellowish area around eyes, frontoclypeal apotome and parietal (Fig. 6A). Yellowish marks divided into three columns with two marks in each column on the frontoclypeal apotome, the stripes on the front left and front right are crescent-shaped, with rest of the marks nearly circular. Anterior margin of frontoclypeal apotome slightly concave, with mediotransversal fold arm conspicuous, anterior margin slightly convex, posterior angle ogival, about 120°. Dorsum of head with dark brown hair-like setae, short and brown truncate peg-like setae and short acuminate peg-like setae. Head in lateral view nearly trapezoid, parietal almost yellowish, eyes oval and black (Fig. 6B). In ventral view (Fig. 6C), pair of files brown, parietals otherwise yellow; anterior ventral apotome nearly triangular, brown, with anterior border slightly concave and anterolateral angles rounded. Ventral ecdysial line about 3 times the length of anterior ventral apotome. Posterior ventral apotome tiny, triangular, brown. There is a concave-shaped triangle at 2/3 distance posterior of ventral ecdysial line. Mandibles (Fig. 6D) triangular, dark yellow basally and mostly brown in ventral view, each with two apical teeth and 3 subapicomesal teeth; left mandible with about 10 setae at lateral margin and with brush of about dozen stiff hairs at middle of inner side. Right and left mandibles nearly symmetrical. Submentum (Fig. 6E) in ventral view with basal 2/3 somewhat trapezoidal and distal 1/3 divided, forming two lobes, two lobes nearly oval, posterior margin slightly convex posteriorly. Each anterolateral corner with few long setae and many short setae and each posterolateral corner with stout, short setae. Maxilla (Fig. 6E) each with cardo drop-shaped, brown, stipes.

Figure 6.  

Head of H. kozhantschikovi. A dorsal; B right lateral; C ventral; D left mandible, dorsal; E submentum, cardo and anterior ventral apotome, ventral.

Thorax. Pronotum (Fig. 7A) subrectangular and yellowish-brown, with its width about 4 times its length in dorsal view, subdivided by mid-dorsal ecdysial line. Anterior margin straight and dark brown, posterior margin slightly concave black or dark brown. Pronotum covered with many brown short acuminate peg-like setae, hair-like setae and few truncate peg-hair setae in dorsal view. Prosternal plate large (Fig. 7B), nearly trapezoidal, with its width about 5 times its length; anterior margin blackish, slightly sinuous and slightly convex anteriorly on meson, posterior margin slightly concave. Intersegmental fold often covering two pairs of sclerites posterior of prosternal sclerite; on each side, lateral and submesal sclerite pieces behind prosternal sclerite fused into subrhombic sclerites (Fig. 7B) and with width about 3.5 times its length. Mesonotum (Fig. 7C) yellow brown in dorsal view, undivided on mid-line, with anterior margin straight, anterolateral angles and lateral margins and posterolateral angles black, pair of tint lines issuing from anterolateral angles extending anteromesad to level of ends of V-shaped black mark on middle of posterior margin, each line with anteromesal end bulging and darkened. Diagonal grooves indistinct. Anterior margin with many black hair-like setae and few truncate or acuminate peg-like setae. Metanotum (Fig. 7D) subrectangular and lighter than pronotum and mesonota in lightly yellowish-brown and undivided on mid-line in dorsal view. Anterior margin slightly sinuous, convex anteriorly on meson. Posterior margin shallowly concave, slightly sinuous black mark on middle of posterior margin, anterolateral angles and lateral margins black; broad and deep diagonal grooves issuing from anterolateral angles and more conspicuous than those of mesonotum extending 2/3 distance towards posterior meson of notum. Muscle scars darker than background, longitudinally arranged. Setae on mesonotum and metanotum less dense than those on pronotum. Mesosternum and metasternum with one and two pairs of single-stemmed ventral gills, respectively.

Figure 7.  

Thorax of H. kozhantschikovi Martynov, 1924. A pronotum, dorsal; B prosternal plates and posterior prosternal sclerites, ventral; C mesonotum, dorsal; D metanotum, dorsal.

Legs. Legs yellowish-brown. Forelegs slightly shorter and thicker in structure than mid- and hind legs (Fig. 8A, 7C and 7D). Each fore-trochantin bifurcate (Fig. 8B), two branches divergent at angle of about 90º, with about 10 setae, upper branch slender, lower one stout. Fore-coxae shorter than mid- and hind coxae and somewhat conical, mid- and hind coxae are relatively long and shaped cylindrical in lateral view. Trochanters (Fig. 8B) 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 20 spike-like setae and two-three long slender setae. Fore-femora in lateral view pentagonal, dorsal and ventral margins with dense long slender setae and spike-like setae, respectively. Fore-tibiae and fore-tarsi shorter and stouter than mid- and hind tibiae and tarsi. Mid- and hind femora cylindrical, with few long slender setae and several shorter spike-like setae. Trochanters each two-segmented and approximately triangular, with dense spike-like setae and some long slender setae. Every tibiae and tarsus shaped like tube, forelegs are stouter than those of mid- and hind legs. Tarsal claws slightly curved downwards, of which mid-legs and hind legs fork.

Figure 8.  

Legs and abdomen of H. kozhantschikovi. A right foreleg, right lateral; B right propleuron, right lateral; C right mid-leg, right lateral; D right hind-leg, right lateral; E setae of abdominal tergum VI, left dorsolateral; F plates on abdominal sterna VIII and IX, ventral; G anal prolegs, left lateral.

Abdomen. Abdominal segments I–IX covered densely with slender, dark hair-like setae, segments I–VIII also covered with flat end, brown scale-hair setae (Fig. 8E). There is one long slender seta at each of the sa2 of the abdominal segments I–VII. Abdominal sterna with three types of gills: bifid-stemmed gill, single-stemmed gill and pupal gill. The gill distribution pattern is similar to that of H. briareus. Subtriangular sterna of segments VIII and IX each with pair of ventral plates (Fig. 8F). Pair of sternites VIII subtriangular, yellowish-brown, covered with acuminate peg-like setae; posterior margin of these sternites with long, dark brown spike-like setae. Pair of sternites IX subtrapezoid, yellowish-brown; acuminate peg-like setae on posterior parts of these sternites longer and thicker than those of segment VIII; posterior margin also covered with long, dark brown spike-like setae. Anal prolegs and claws yellowish-brown (Fig. 8G). Anal claws hook-like, angled about 60º, basal part of anal prolegs with about 30 long slender setae.

The larva of H. kozhantschikovi can be diagnosed by the combination of the following features: (1) frontoclypeal apotome with posterior angle ogival, about 120°, with posterior portion of each frontoclypeal suture slightly sinuous; (2) frontoclypeal apotome have yellow stripes divided into three columns with two patches in each column on the frontoclypeal apotome, the stripes on the front left and front right being crescent-shaped, while the rest are circular; (3) each fore-trochantin bifurcate, two branches divergent at angle of about 90º.