Hydropsyche trifora (Li & Tian 1990)

Xu, Ji-Hua, Sun, Chang-Hai & Wang, Bei-Xin, 2018, Descriptions of larvae of three species of Hydropsyche (Trichoptera, Hydropsychidae) from China, Zootaxa 4374 (1), pp. 1-24 : 17-23

Hydropsyche trifora (Li & Tian 1990) , Ceratopsyche

( Figs. 12–15 )

Description. Larvae (5th instar). Body length 10–15 mm (n = 5). Head. Head capsule ( Fig. 12A ) subquadrate in dorsal view, 1.7 mm long, 1.2 mm wide at midlength. Overall coloration mostly dark brown, with 3 yellow oval patches longitudinally arranged on frontoclypeal apotome, of which anterior one largest, middle one second, and posterior one smallest; in dorsal view parietals each with oblique pale brown stripe along posterolateral margin; in lateral view each stripe and yellow area around each eye fused into U-shaped patch, collectively resembling shoulders, neck, and head of bird ( Fig. 12C ); muscle scars on parietals dark brown ( Fig. 12A , msc), and those on postgenae light brown. Eyes oval, black. Frontoclypeal apotome ogival, with frontoclypeal suture arms slightly sinuous. Dorsum of head with hair-like setae, dark brown truncate peg-like setae, and acuminate peg-like setae. Labrum yellow, with its anterior margin round and hair brush at each anterolateral corner. Mandibles ( Fig. 12D ) yellow, triangular in ventral view, each with 5 apical teeth; left mandible with about 20 setae at basal half of lateral margin and with brush of stiff hairs at middle of inner side; right mandible with more than 20 setae at basal half of lateral side. Maxillae each with cardo transverse and sub-rectangular, brown ( Figs 12B, 12F ); stipes oblique and subrectangular, palpifer with about 29 setae, palp 5-segmented, and maxillary lobe adjacent to mesal margin of palp ( Fig. 12G ). Labium ( Fig. 12G ) triangular and short in ventral view. Submentum ( Fig. 12E ) in ventral view with basal 2/3rds somewhat trapezoidal and distal 1/3rd incised mesally, forming two lobes; posterior margin slightly convex posteriorly; each anterolateral corner with 3–5 long, strong setae and many short setae; each posterolateral corner bearing stout, brown setae. Anterior ventral apotome ( Fig. 12B ) nearly triangular, brown, with anterior margin slightly concave and anterolateral angles rounded. Ventral ecdysial line about twice as long as anterior ventral apotome. Posterior ventral apotome tiny, triangular, brown.

Thorax. Pronotum ( Fig. 13A ) dark brown, sub-rectangular and subdivided longitudinally, covered with hairlike setae, truncate peg-like setae, and acuminate peg-like setae; three types of setae alternatively arranged along anterior margin, with 2 types of peg-like setae as long as hair-like setae; muscle scars distinct; prosternal plate ( Fig. 13E ) dark brown in posterior 2/3rds, pale in anterior 1/3 except with dark anterior border, with its width about 7 times its length, anterior margin sinuous and convex anteromesally, posterior margin slightly sinuous and concave posteromesally; lateral piece and median piece behind each end of posterior prosternal sclerite fused into subrectangular piece on each side, each with anterolateral and posteromesal corners acute. Mesonotum ( Fig. 13B ) dark brown dorsomesally, then gradually paler laterally, but lateral borders black, anterior margin with lateral portion black, middle portion brown, U-shaped posterior marking black and pair of lateral fusiform marks indistinct; muscle scars darker, distinct, longitudinally arranged; hair-like setae and 2 types of peg-like setae scattered over surface of notum. Metanotum ( Fig. 13C ) lighter than pro- and mesonota; color patterns similar to those of mesonotum, but dorsomesal stripe much narrower; posterior marking straight; anterior margin mostly with hair-like setae and dotted with truncate peg-like setae; posteromesal margin with 6–7 teeth.

Legs. Legs yellow to brown. Forelegs shorter and stouter than mid- and hind legs ( Figs. 14A – 15C ). Each foretrochantin bifurcate ( Fig. 13D ), two branches divergent about 70°, with about 15 setae. Forecoxae somewhat conical; those of mid- and hind legs cylindrical. Trochanters triangular and 2-segmented, each with basal segment subtriangular and shorter than subtriangular apical segment, ventral trochanteral brush present on forelegs, with more than 15 spike-like setae. Forefemora in lateral view pentagonal, each with dorsal margin angulate and lower margin possessing dense long-slender setae and spike-like setae, mid- and hind femora cylindrical, with each lower margin bearing spike-like setae. Each tibia and tarsus more slender than its femur. Tarsal claw of each foreleg stout, about half as long as its tarsus, curved slightly downwards, its basal seta slender; that of each midleg about half as long as its tarsus, with its base thick, curved slightly downwards, with apex acute; that of each hind leg about 1/3rd as long as its tarsus, curved about 90°.

Abdomen. Abdominal segments I–IX ( Fig. 13F ) covered with black hair-like setae and sparsely scattered with flattened scale -hair setae (arrows). Dorsolateral areas (sa 2) of segments I–VII with 3 long setae on each side. Tergum IX with distinct pair of triangular tergites covered with hair-like setae and each with 4 long-slender setae at posterior margin ( Fig. 13G ); sterna of segments VIII–IX each with pair of ventral plates, covered with spike-like setae. Anal prolegs slightly sclerotized, heavily setose apically; anal claws yellowish brown, hook-like, angled about 90° ( Fig. 13H ).

Diagnosis. See diagnosis for H. columnata .

Materials examined. CHINA, An-hui Province : 6 larvae, Huang-shan , Tang-kou Town, Fu-xi-cun, Fu-xi, 30.24°N, 118.54°E, alt. 614 m, 13 Jul. 2015, by Bei-xin Wang & Shu-zhao Gao . Zhe-jiang Province : 3 males, Lin-an , Gao-hong Town, Mt. Da-shan, 30.39°N, 119.62°E, alt. 507 m, 9 May 2015, by Ji-hua Xu, Si-wen He & Shu-zhao Gao.

Known distribution. China (An-hui, Gui-zhou, He-nan, Jiang-xi, Shaan-xi).

Key to 5th instar larvae of 15 Chinese Hydropsyche species

1. Dorsum of head uniformly black or blackish brown, except for small area around eye ( Hur et al. 2000, fig. 1)............ 2

- Dorsum of head with marks or stripes ( Figs. 3A , 6A , 9A , 12A )................................................. 3

2. Posterolateral corners of parietals black to pale brown, with distinct muscle scars near coronal suture, Yunnan ( Zhou 2007, fig. 24a).......................................................................... H. grahami (morphotype c1)

- Posterolateral corners of parietals light yellow, without muscle scars ( Hur et al. 2000, fig. 1)... H. orientalis Martynov 1934

3. Anterior margin of frontoclypeal apotome not straight, with teeth or notably convex ( Lepneva 1964, fig. 678; Zhou 2007, fig. 28a)................................................................................................ 4

- Anterior margin of frontoclypeal apotome straight or slightly concave ( Figs. 3A , 6A , 9A , 12A )....................... 5

4. Anterior margin of frontoclypeus with upturned tooth or denticle on each side ( Lepneva 1964, fig. 678)............................................................................................... H. ornatula McLachlan 1878

- Anterior margin of frontoclypeus asymmetrical, more convex on right side than on left side ( Zhou 2007, fig. 28a).................................................................... H. quadrata ( Li & Dudgeon 1990, in Li et al. 1990)

5. Frontoclypeal apotome without marks, stripes or spots; but with paired longitudinal stripes along frontoclypeal sutures from base to anterior ends ( Fig. 3A ; Zhou 2007, fig. 25a).......................................................... 6

- Frontoclypeal apotome with diverse marks, stripes or spots; without longitudinal stripes along frontoclypeal sutures from base to anterior ends ( Figs. 6A , 9A , 12A ; Lepneva 1964, fig. 678).................................................. 7

6. Metanotum with distinct longitudinal stripes (Zhou 2007, figs. 25a, 25c)..................... H. formosana Ulmer 1911

- Metanotum yellow, without stripes ( Fig. 4B ).............................. H. arion Malicky & Chantaramongkol 2000

7. Triangular anterior ventral apotome nearly isosceles; anterior margin of ventral ecdysial line with shallow notch ( Lepneva 1964, fig. 678)................................................................. H. pellucidula (Curtis 1934)

- Triangular anterior ventral apotome nearly equilateral; anterior margin of ventral ecdysial line with deep notch ( Figs. 6B , 9B , 12B )............................................................................................... 8

8. Dark marks on frontoclypeal apotome A-shaped from base to mediotransversal folding (Zhou 2007, figs. 21a, 22a)....... 9

- Dark marks on frontoclypeal apotome not A-shaped, but with oval marks ( Figs. 6A , 9A , 12A ), or more than two pairs of stripes ( Zhou 2007, fig. 26a)........................................................................... 10

9. Center of frontoclypeal apotome without peg-like setae ( Zhou 2007, fig. 22a).................. H. furcula Tian & Li 1985

- Center of frontoclypeal apotome with numerous truncate peg-like setae, Guangdong, Guangxi ( Zhou 2007, fig. 21a).......................................................................... H. grahami Banks 1940 (morphotype c10)

10. Anterior margin of submentum with shallow notch, much shorter than half of mesal line of basal submentum ( Zhou 2007, fig. 26b)........................................................................ H. polyacantha Li & Tian 1989

- Anterior margin of submentum with deep notch, at least half as long as mesal line of basal submentum ( Figs. 6E , 9E , 12E ) 11

11. Trochantin each with two branches divergent less than 90° ( Fig. 13D )........................................... 12

- Trochantin each with two branches divergent about 90° ( Figs. 7D , 10D )......................................... 13

12. Prosternal plate with its width about 6 times its length ( Fig. 13E )........................................ H. trifora

- Prosternal plate with its width about 4 times its length (Zhou 2007, fig. 19f)................. H. fukienensis Schmid 1965

13. Frontoclypeal apotome with 7–9 light marks ( Lepneva 1964, fig. 703)........................ H. newae Kolenati 1858

- Frontoclypeal apotome with fewer marks ( Figs. 6A , 9A )..................................................... 14

14. Pronotum with two dark brown stripes and two yellow transverse stripes ( Fig. 10A )........................ H. simulata

- Pronotum yellow or dark brown, without stripes or marks ( Fig. 7A )............................................ 15

15. Frontoclypeal apotome with three longitudinal oval marks ( Fig. 6A )................................... H. columnata

- Frontoclypeal apotome with two prominent marks ( Zhou 2007, fig. 20a).................... H. serpentina Schmid 1965

Figures

FIGURE 3. Head of Hydropsyche arion Malicky & Chantaramongkol 2000.3A, dorsal; 3B, ventral; 3C, right lateral; 3D, left mandible, ventral; 3E, submentum, ventral; 3F, maxillae (without cardines) and labium, ventral. avp. = anterior ventral apotome; car. = cardo; fap. = frontoclypeal apotome; lab. = labrum; pos. = postgenae; pva. = posterior ventral apotome; vel. = ventral ecdysial line.Scale bars 0.1 mm.

FIGURE 4. Thorax and abdomen of Hydropsyche arion Malicky & Chantaramongkol 2000. 4A, pronotum, dorsal; 4B, mesonotum, dorsal; 4C, metanotum, dorsal; 4D, right propleuron, right lateral; 4E, prosternal plates and posterior prosternal sclerites, ventral; 4F, setae of abdominal tergum VII, right lateral; 4G, tergum IX, dorsal; 4H. anal prolegs, left lateral. apr. = anal prolegs; lfm. = lateral fusiform marks; lpi. = lateral piece; mpi. = median piece; msc. = muscle scars; pma. = posterior marks; ppl. = prosternal plate.Scale bars 0.1 mm.

FIGURE 6. Head of Hydropsyche columnata Martynov 1931. 6A, dorsal; 6B, ventral; 6C, right lateral; 6D, left mandible, ventral; 6E, submentum, ventral; 6F, cardines and anteroventral apotome, ventral; 6G, maxillae (without cardines) and labium, ventral. Scale bars A, B, C = 0.2 mm; D, E, F, G = 0.1 mm.

FIGURE 7. Thorax and abdomen of Hydropsyche columnata Martynov 1931. 7A, pronotum, dorsal; 7B, mesonotum, dorsal; 7C, metanotum, dorsal; 7D, right propleuron, right lateral; 7E, prosternal plates and posterior prosternal sclerites, ventral; 7F, setae of abdominal tergum VIII, right lateral; 7G, tergum IX, dorsal; 7H, anal prolegs, left lateral.Scale bars 0.1 mm.

FIGURE 9. Head of Hydropsyche simulata Mosely, 1942 9A, dorsal; 9B, ventral; 9C, right lateral; 9D, left mandible, ventral; 9E, submentum, ventral; 9F, maxillae (without cardines) and labium, ventral. Scale bars 0.1 mm.

FIGURE 10. Thorax and abdomen of Hydropsyche simulata Mosely 1942. 10A, pronotum, dorsal; 10B, mesonotum, dorsal; 10C, metanotum, dorsal; 10D, right propleuron, right lateral; 10E, prosternal plates and posterior prosternal sclerites, ventral; 10F, setae of abdominal tergum VII, left lateral; 10G, tergum IX, dorsal; 10H, anal prolegs, left lateral.Scale bars 0.1 mm.

FIGURE 12. Head of Hydropsyche trifora Li & Tian, 1990. 12A, dorsal; 12B, ventral; 12C, right lateral; 12D, left mandible, ventral; 12E, submentum, ventral; 12F, cardines and anteroventral apotome, ventral; 12G, maxillae (without cardines) and labium, ventral. Scale bars 0.1 mm.

FIGURE 13. Thorax and abdomen of Hydropsyche trifora Li & Tian 1990. 13A, pronotum, dorsal; 13B, mesonotum, dorsal; 13C, metanotum, dorsal; 13D, right propleuron, right lateral; 13E, prosternal plates and posterior prosternal sclerites, ventral; 13F, setae of abdominal tergum VII, right lateral; 13G, tergum IX, dorsal; 13H, anal prolegs, left lateral.Scale bars 0.1 mm.

FIGURE 14. Legs of Hydropsyche trifora Li & Tian 1990. 14A, right foreleg, right posterolateral; 14B, right midleg, right posterolateral; 14C, right hind leg, right posterolateral.Scale bar 0.2 mm.

FIGURE 15. Right lateral habiti of 4 Hydropsyche species in alcohol. 15A, Hydropsyche arion Malicky & Chantaramongkol 2000; 15B, Hydropsychecolumnata Martynov 1931; 15C, Hydropsyche simulata Mosely 1942; 15D, Hydropsyche trifora Li & Tian 1990. Scale bar 0.5mm.