Cerconychia flectospina Wu, 1962

Chen, Zhi-Teng, 2023, The little-known larval morphology of two stoneflies of Styloperlidae (Insecta: Plecoptera) in China, Zootaxa 5244 (4), pp. 361-376 : 369-371

Cerconychia flectospina Wu, 1962

Figs. 10–17

Material examined. China: Yunnan: Mt. Ailao ( Fig. 10A ), 23°56'54.96"N, 101°30'25.2"E, 2300 m, 21 male adults ( Fig. 10B ), 1 female adult, 6 larvae, 8–9. vii. 2022, leg. Zhi-Teng Chen (ICJUST) .

Description of mature male larvae. Body slender, length ca. 12 mm (excluding antennae and cerci), generally pale brown, without gills ( Fig. 11A, B ).

Head. Generally brown, covered by sparse fine hairs, lateral margins fringed with several erected long setae ( Fig. 12A–C ). Biocellate. Clypeus covered with dense short setae on posterior half. Ecdysial suture distinct. Compound eyes small, dark, with sparse short setae on posterior half; each eye with a pair of long setae along inner margin. Occiput covered with dense, prostrate setae on posterolateral areas. Antennae slender ( Fig. 12D ), subequal in length to abdomen, generally pale brown; scapus with an apical fringe of dense, stout setae which interrupted laterally; other segments apically fringed with sparse, short setae.

Mouthparts. Labrum with a transverse patch of dense long setae which interrupted medially and two anterolateral patches of moderate setae ( Fig. 13A ). Submentum rounded, covered by dense long setae ( Fig. 13B ). Apical segment of labial palp subequal in length to the penultimate one, apex covered with stout setae ( Fig. 13B ). Paraglossae slightly larger than glossae which are separated from each other by a median sclerite ( Fig. 13B ). Cardo of maxilla slender, dorsally and laterally with a few long setae ( Fig. 14A–D ). Stipes broad, covered with long setae on both dorsal and ventral surfaces. Galea finger-shaped, outer margin fringed with curved hairs on apical half and flattened moderate setae throughout, inner margin with a comb of erected setae in the middle, apex with a bunch of stout setae. Lacinia slightly shorter than galea, with three apical teeth, inner margin with a row of long setae extending both dorsad and ventrad, dorsal surface with a subapical row of moderate setae near the marginal setae. Maxillary palp segments III–V equal in length, apex with stout setae. Right mandible with three apical teeth whose line is prolonged posteriorly to the end of inner margin ( Fig. 15A, B ). Left mandible with four apical teeth whose line is prolonged posteriorly into the ventral humps on the mola ( Fig. 15C, D ). Left mola with a blade-like inner edge on dorsal surface; right mola with inner marginal concave areas on dorsal surface. Both molae with a row of long hairs on posterointernal margin which connected or interrupted with a dorsal patch of short hairs near apical teeth.

Thorax. Pronotum subquadrate, near as wide as head, length two times shorter than width, outline dark, corners obtuse and each with about two erect, long setae ( Fig. 12A–C ); background pigmentation pale brown, median suture and its two lateral longitudinal bands dark brown, surface covered with hairs. Meso- and metanota background pigmentation pale, most areas covered with dense, dark setae. Wing pads with equal sizes, pale, covered with setae similar to those on meso- and metanota, ventral surface with dense long spines on basal half, inner margins concave in both forewing pads and hind wing pads ( Fig. 12A, B ). Thoracic sterna covered with brown hairs ( Fig. 12C ); median pits of each sternum pale. Spinasternum of prothorax separated from furcasternum ( Fig. 12C ).

Legs. Coxae and trochanters covered with dark setae and fringed with stout spines mainly on dorsal surfaces ( Figs. 12A–C and 16A–F ). Femora dorsally covered with dense dark setae except for a longitudinal glabrous stripe near outer margin, and with several scattered giant spines, ventrally covered with sparse setae, anterior margin fringed with several short dark spines, posterior margin with dense patch of stout spines. Tibiae covered with dense dark setae on both dorsal and ventral surfaces, inner and outer margins fringed with dense stout spines, outer margin with dense long swimming hairs, distal margin fringed with stout trifurcate setae but without spurs ( Fig. 16A–G ). Tarsal segments covered with dense setae; the first two tarsal segments shortest, apical tarsal segment of foreleg and midleg with bud-like setae. Claws sharp and glabrous.

Abdomen. Abdominal sternum I fused with metasternum, segment II divided into terga and sterna by membranous pleura ( Fig. 17A, B ); each segment covered with dense dark brown setae on both dorsal and ventral aspects, and fringed with dense moderate setae along posterior margin. Tergum X with rounded posterior margin. Paraprocts triangular, generally sclerotized, covered with both thin and thick setae. Cerci generally pale brown ( Fig. 17C ), much shorter than abdomen; each segment with apical fringe of both stout and long setae, length of the longest setae exceeds the segment length.

Distribution. The species is known from Yunnan Province of southern China and Sapa of Vietnam ( Zhao et al. 2020).

Figures

FIGURE 10. Cerconychia flectospina Wu, 1962. (A) Habitat in Mt. Ailao, Yunnan, China. (B) Habitus of living male adult.

FIGURE 11. Cerconychia flectospina Wu, 1962, male larva. (A) Habitus, dorsal view. (B) Habitus, ventral view. Scale bars, 1.0 mm.

FIGURE 12. Cerconychia flectospina Wu, 1962, male larva. (A) Head and thorax, dorsal view. (B) Head and thorax, lateral view. (C) Head and thorax, ventral view. (D) Basal and apical segments of antenna, lateral view. Scale bars, 1.0 mm for (A–C), 0.1 mm for (D).

FIGURE 13. Cerconychia flectospina Wu, 1962, male larva. (A) Labrum, dorsal view. (B) Submentum, ventral view. Scale bars, 0.1 mm.

FIGURE 14. Cerconychia flectospina Wu, 1962, male larva. (A) Right maxilla, ventral view. (B) Left maxilla, dorsal view. (C) Left maxilla, dorsal view. (D) Right maxilla, dorsal view. Scale bars, 0.1 mm.

FIGURE 15. Cerconychia flectospina Wu, 1962, male larva. (A) Right mandible, ventral view. (B) Right mandible, dorsal view. (C) Left mandible, dorsal view. (D) Left mandible, ventral view. Scale bars, 0.1 mm.

FIGURE 16. Cerconychia flectospina Wu, 1962, male larva. (A) Left foreleg, dorsal view. (B) Left foreleg, ventral view. (C) Left midleg, dorsal view. (D) Left midleg, ventral view. (E) Left hind leg, dorsal view. (F) Left hind leg, ventral view. (G) Details on apex of left hind leg, dorsal view. Scale bars, 0.5 mm.

FIGURE 17. Cerconychia flectospina Wu, 1962, male larva. (A) Abdomen, dorsal view. (B) Abdomen, ventral view. (C) Basal segments of cercus, lateral view. Scale bars, 1.0 mm for (A–B), 0.1 mm for (C).