Hydropsyche briareus Malicky & Chantaramongkol, 2000

Hydropsyche briareus Malicky & Chantaramongkol, 2000

Materials

Type status: Other material. Occurrence: sex: 2 males; lifeStage: 2 adults, 3 larvae; occurrenceID: EBD13007-C109-5C60-AC1B-6985D2E586FF; Location: country: China; stateProvince: Sichuan; county: Ningnan; locality: Hulukou Town, Heishui River ; verbatimElevation: 610 m; verbatimLatitude: 26°57'46"N; verbatimLongitude: 102°48'27"E; verbatimCoordinateSystem: degrees minutes seconds; Identification: identifiedBy: Xinyu Ge; Event: samplingProtocol: UV light trap, D-frame aquatic net; eventDate: 22 Nov 2023; Record Level: institutionCode: Tianjin Normal University, Tianjin, China (TJNU) GoogleMaps

Type status: Other material. Occurrence: lifeStage: 2 larvae; occurrenceID: 4E6E270B-B296-5096-89AE-7FDF792F9C2F; Location: country: China; stateProvince: Yunnan; county: Yuanmou; locality: Jianshe Village, Longchuan River ; verbatimElevation: 880 m; verbatimLatitude: 25°57'39"N; verbatimLongitude: 101°52'28"E; verbatimCoordinateSystem: degrees minutes seconds; Identification: identifiedBy: Xinyu Ge; Event: samplingProtocol: D-frame aquatic net; eventDate: 19 Nov 2023; Record Level: institutionCode: Tianjin Normal University, Tianjin, China (TJNU) GoogleMaps

Description

Mean length of 5 th instar larvae is about 15 mm (n = 5). Overall body length is similar to most hydropsychid larvae (Fig. 1 View Figure 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.

Head. The head is rectangular in dorsal view, about 1.9 mm long and 1.7 mm wide (Fig. 2 View Figure 2 A). 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. 2 View Figure 2 B). In ventral view, anterior ventral apotome nearly triangular, with anterior border slightly concave and anterolateral angles rounded (Fig. 2 View Figure 2 C). 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. 2 D), 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. 2 View Figure 2 E) 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.

Thorax. Pronotum (Fig. 3 View Figure 3 A) 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. 3 View Figure 3 B) 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. 3 View Figure 3 C) subrectangular and lightly yellowish-brown in dorsal view, covered with dark hair-like setae and truncate peg-hair setae, one long setae at positions sa 2. Anterior margin approaching a straight line in brown; posterior margin mark black, concave slightly inward and U-shaped in the middle. Metanotum (Fig. 3 View Figure 3 D) 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.

Legs. Legs yellowish-brown. Forelegs slightly shorter and thicker than mid- and hind legs (Fig. 4 View Figure 4 A, 4 C and 4 D). Each fore-trochantin short and thick bifurcated, upper branch slender, lower one stout, two branches divergent at angle of about 90 º, 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.

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. 4 View Figure 4 E). There is one long slender seta at each of the sa 2 of the abdominal segments I – VII. Subtriangular sterna of segments VIII and IX each with pair of ventral plates (Fig. 4 View Figure 4 F), 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. 4 View Figure 4 G), each slightly sclerotised with spike-like setae and apical part with about 25 long slender setae arranged in one plane. Anal claws (Fig. 4 View Figure 4 G) hook-like, angled about 60 º.

Diagnosis

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.