Potamyia chinensis ( Ulmer 1915 )

Zhang, Ao & Zhou, Xin, 2021, The larvae of Chinese Hydropsychidae (Insecta: Trichoptera), Part II: Potamyia chinensis and Cheumatopsyche trifascia, Zootaxa 4926 (4), pp. 547-558 : 551-553

Potamyia chinensis ( Ulmer 1915)

( Figs 2 a–2j)

HEAD. Head sub-quadrate, lateral sides of head parallel with each other, 1.0 mm long, 0.8 mm wide. Anterior margin of frontoclypeal apotome straight, crenulate, with series of tiny tooth-like structures. Lateral sides of frontoclypeal apotome narrower at eye level. Mediotransversal fold of frontoclypeal apotome not prominent ( Fig. 2a ).

Anterior margin of frontoclypeus pigmented, reddish brown, both anterolateral corners brownish. Rest of frontoclypeal apotome mostly light brownish, with four pale yellowish markings: anterior marking situated on middle of anterior margin, large (almost one-fourth as long as entire length of frontoclypeus, and one-third as wide as width of front margin), more or less rectangular; two lateral markings small, sub-triangular, each with tentorial pit situated on short posterior border; posterior marking situated on middle of frontoclypeus, rounded. Parietal sclerite on each side mostly pale yellowish; area along frontoclypeal suture and anterior half of coronal suture darker; this darker area extended ventrolaterad behind eye, not reaching ventral side of head ( Fig. 2c ). Posterodorsal margins of parietal sclerites bearing transverse brownish thin stripes.

Primary setae very long; secondary setae on anterolateral corners of frontoclypeus longer than those on rest of dorsal head. All secondary setae relatively long, fine, tapered, bearing prominent sockets, brownish (on dark background) or yellowish (on pale background). Frontoclypeus evenly distributed with fine secondary setae.

Ventral side of head mostly pale yellow; striae on middle half of each stridulating file darker; pair of stridulating files connected mesally by transverse dark band anterior of setae #18 ( Fig. 2b ). Anterior ventral apotome darker, sub-triangular, shorter than one-fourth of ventral ecdysial line, anterior margin mostly concave, slightly protrusive in middle; posterior ventral apotome minute, triangular. Submentum trapezoidal, lateral sides slightly concave in middle; posterior border curved; anterior margin cleft, middle incision narrow and straight, anterior borders of lateral lobes oblique, shorter mesally than laterally. Lateral region of each parietal sclerite bearing long, tapered, clear secondary setae on anterior half.

THORAX. Thoracic nota yellowish, without prominent markings, densely covered by long, tapered, hair-like secondary setae. Anterior border of each notum bearing dense series of long, tapered setae.

Seta 22 on anterolateral corner of each side of pronotum prominent, long and thick ( Fig. 2d, 2e ). Posterior border of pronotum with thin, brownish line; lateral borders black.

Prosternal plate large, followed posterolaterally by pair of small, sub-triangular, posterior prosternal sclerites ( Fig. 2f ).

Foretrochantin finger-like, not forked, yellowish, bearing few thick, long, black bristles on dorsal and lateral surfaces. Apex of foretrochantin slightly curved upward, pointing cephalad ( Fig. 2g ).

Hair-like setae on meso- and metanota longer and thicker than those on pronotum. Middle third of lateral border of mesonotum paler, brownish, whereas rest of lateral border black. Posterior border of mesonotum with curved, black marking on middle half; this mark with no lateral pieces.

Anterior fourth of lateral border of metanotum black, thicker; remainder of lateral border with thin dark brownish line. Posterior border of metanotum with small, round black mark on middle. Secondary setae sparser than those on mesonotum.

Mesosternum with one pair of ventral tracheal gills; metasternum with two pairs of ventral tracheal gills ( Table 2). All thoracic gills single-stemmed.

ABDOMEN. Abdominal terga and pleura covered by only one type of secondary setae: each moderately long, fine, with apex slightly enlarged and more or less flattened ( Fig. 2i ). Density of secondary setae somewhat sparse, usually separated by distance greater than lengths of setae.

Lateral gills on abdominal pleura simple, finger-like, long. Abdominal segments I, II, VIII, and IX with no lateral gills; segment III with one pair of lateral gill; segments V–VI with three pairs of lateral gills; VII with two pairs of lateral gills, posterior gills small, short and conical ( Fig. 2j ; Table 2).

Abdominal ventral gills of two typical hydropsychid types: single-stemmed gills and bifid-stemmed gills, stalks of all gills not segmented. Single-stemmed gills situated anteromesad of bifid gills on segments II–VI. Abdominal segment I with two pairs of single-stemmed gills (ventrolateral and ventromesal), situated very closely; segments II–VI each with one single-stemmed gill and one bifid gill on each side; segment VII with one pair of singlestemmed gills ( Table 2).

Ventral sternites on abdominal VIII small, triangular, with light yellowish pigmentation. Anterior part of each sternite VIII with tapered, short, thick, golden setae; posterior border with long, thick, dark brownish bristles, pointing posterad. Ventral sternites IX large, sub-triangular, each with posterior border very wide, mesal border straight; light brownish. Golden setae on anterior part of each sternite IX longer than anterior setae on sternites VIII; posterior border with long, thick, brownish bristles, pointing posterad. Posteromesal corner of each sternite IX with seta-less area ( Fig. 2h ).

Diagnosis. The color pattern on the head of Potamyia chinensis somewhat resembles that of Hydropsyche simulata ( Xu et al. 2018) . But these two species can be easily differentiated based on other characters, such as the shape of the anterior ventral apotome, the shape and size of posterior prosternal sclerites, the shape of the foretrochantins, etc.

Figures

FIGURE 2. Potamyia chinensis (Ulmer 1915) larva. 2a, head, dorsal; 2b, head, ventral; 2c, head, left lateral; 2d, pro-, meso-, and metanota, dorsal; 2e, pro-, meso-, and metanota, left lateral; 2f, prosternal plate and posterior prosternal sclerites (latter also shown further enlarged), ventral; 2g, left foretrochantin, left lateral; 2h, right ventral sclerites on sterna VIII and IX, ventral; 2i, hairs on tergum of abdominal segment II; 2j, lateral gills (pleural gills) on left side of abdominal segment V, left lateral.