Skwala compacta ( McLachlan, 1872 ) McLachlan, 1872

Teslenko, Valentina A., 2012, A taxonomic revision of the genus Arcynopteryx Klapálek, 1904 (Plecoptera, Perlodidae), Zootaxa 3329, pp. 1-18 : 14-17

Skwala compacta ( McLachlan, 1872) comb. nov.

( Figs 39–48 )

McLachlan 1872: 52−53, pl. I, figs 6, 7−7b ( Dictyopteryx compacta ); Klapálek 1912: 15 ( Arcynopteryx compacta var. pusilla nov.); Koponen 1949: 12−13, figs 10 А −С ( Arcynopteryx brevis ); Illies 1966: 510 (sp. inquirenda); Raušer 1968: 352−354, figs 47−57 ( Arcynopterygoides vernalis , syn. n.); Zwick et al. 1971: 852−853, figs 6−8 ( Skwala brevis ); Zwick 1973: 239 ( Arcynopteryx brevis ); Stark & Szczytko, 1981: 61−63, figs 1−4 ( Skwala brevis ); Zhiltzova 1982: 116 ( Skwala pusilla = S. brevis ); Zhiltzova & Zapekina-Dulkeit 1986: 184, figs 4−6 ( Skwala pusilla ); Teslenko & Zhiltzova 2009: 17, figs 49−53 ( Skwala pusilla ).

Diagnosis. Abdominal segments 1−2 are divided by a pleural fold. The submental gills are long and conical. The arms of the mesosternal ridge meet the anterior corners of the furcal pits, the transverse suture is absent. The stylet of the epiproct as a long, fine bristle is absent. The male of Skwala compacta comb. nov. can be distinguished by the shape of the hemitergal lobes, which are simple, cylindrical, wide, short, flat and slightly curved upward along the posterior margin. The hemitergal lobes are directed towards the middle transversely, and covered by small, stout setae ( Figs 40−43 ). The lever arm is short, stout and slightly curved; the epiproct is short, blunt and spoon shaped, with a soft distal part and a finger-shaped top ( Fig. 44 ), the top is densely covered with thin, clear spines. The lateral stylets are attached laterally to the folds of the cowl only the pointed sclerotized tips are clearly pronounced ( Fig. 44 ). The everted aedeagus is large and membranous, with a pair of distinct lateral rounded lobes at the dorsolateral margins; one large lobe rounded dorsally is present between the lateral lobes; one small knob is located apically; two broadly rounded swellings project posteriolaterally and slightly below the large lobe; tiny, clear, erect spinules densely cover the aedeagal surface ventrally and laterally; reddish spinules are grouped in a triangle on the dorsal surface of the large lobe basally and continue dorsomedially to the small knob ( Fig. 42 ). The female has a large subgenital plate, its posterior margin slightly rounded and sclerotized, with two shallow notches medially; the plate is covered with small, darkish setae ( Fig. 45 ). The egg is spindle-shaped ( Fig. 46 ). The collar is stalked; the sides of the collar bear several sharp longitudinal carinae ( Fig. 47 ). The chorion is covered with closely packed hexagonal FCIs ( Figs. 46−48 ); the FCI walls are thin, consisting of shallow furrows; the floors are flat with 4-8 small punctations medially ( Fig. 48 ).

Adult habitus. The head is brown, with a yellow spear-shaped spot in the interocellar area, not reaching the median ocellus and continued to the occiput medially, where the spot is slightly enlarged ( Fig. 39 ). A dark brown spot projects onto the clypeus in front of the brownish M-line. The tentorial pits are brown; the lateral margins of the clypeus are pale. The pair of tentorial pits in front of the lateral ocelli and the pair of small oval patches lateral to the lateral ocelli are brown. A posterolateral spot with brown callosities is weakly recognizable behind each compound eye. The antennae and palpi are brown. The pronotum is almost square or slightly longer in width than in length, brown with a yellow medial band and prominent dark brown rugosities ( Fig. 39 ). The medial band expands in the last quarter of the length of the pronotum. The meso- and metanotum are dark brown. The anterior margin of the femur is dark brown. The tibia is light brown with a thin dark brown stripe basally. The wings of the male and female are slightly shortened and extend to the top of the abdomen. The RS of the forewing has three or more branches; the apex exhibits a random network of cells formed by the transverse veins and branches of the RS. The cerci are longer than the abdomen, ringed, and covered with long colorless hairs. Each cercal segment is pale basally and blackish distally. The apical cercal segments are completely blackish with the exception of the pale bases ( Fig. 39 ). The submental gills are long and conical. The arms of the mesosternal ridge meet the anterior corners of the furcal pits, a transverse suture is absent.

Male. Body length 11.5−14.5 mm, forewing 8.0−11.0 mm, wingspan 17.2–23.5 mm. Abdominal tergum 9 exhibits a thin, transversal, membranous, brownish median band and one indistinct small pale spot anteromedially ( Figs. 41 & 42 ). The posterior margin of tergum 9 bears a notch along 1/3 of the length of tergum 9 and two transversely elongated and rounded swellings, which are covered by small stout setae and fine colorless hairs posteriolaterally ( Fig. 41 ). Sternum 9 is scoop-shaped, extended backward and upward, pointed at the top ( Figs 40 & 41 ). Tergum 10 is divided into two hemiterga. The hemitergal lobes in dorsal view are simple, cylindrical, wide, short, flat and slightly curved upward along the posterior margin, directed towards the middle transversely, and covered by small, stout setae ( Figs 40−43 ). The cowl is membranous, folded, resembles a pouch between and under the hemitergal lobes, attached around the sclerites of the internal basal anchor. The cowl opens dorsally with a slit. The dorsolateral edges of the cowl are supported by flat, band-like sclerotized paragenital plates ( Fig. 42 ). In a lateral view, the internal basal anchor is rounded anteriorly, the arrow-like sclerites are black and hidden under tergum 9 ( Fig. 42 ). The lever arm is short, stout, slightly curved, hollowed and connected to the epiproct distally ( Fig. 44 ). The epiproct is short, blunt, spoon shaped, sclerotized basally and ventrally; its distal part is soft ( Fig. 44 ). The top of the distal part is finger-shaped, densely covered with thin, clear spines. Lateral stylets are attached to the folds of the cowl laterally; their acute sclerotized tops clearly pronounced ( Fig. 44 ). The everted aedeagus is large and membranous, in a dorsal view with a pair of finger-like lobes at the dorsolateral margins; one large dorsally rounded lobe is set between the lateral lobes; one small rounded knob located apically; two broadly rounded swellings project posteriolaterally and slightly below the large lobe; tiny, clear, erect spinules densely cover the aedeagal surface ventrally and laterally; reddish spinules are grouped in a triangle on the dorsal surface of the large lobe basally and continued dorsomedially to the small knob ( Fig. 42 ).

Female is larger than male and similar to male in shape and color. Body length 12.0− 16.2 mm, forewing 14.0− 17.5 mm, wingspan 30.0−37.0 mm. Sternum 8 is pale medially. The subgenital plate is large, extends laterally from the sides of sternum 8, and reaches almost half the length of sternum 9; the posterior margin is slightly rounded and sclerotized, with two shallow notches medially ( Fig. 45 ). The subgenital plate is covered with small, darkish setae. Sterna 9, 10 are pale, sternum 9 with two brownish rounded spots mesolaterally ( Fig. 45 ).

Egg is spindle-shaped ( Fig. 46 ) and circular in cross-section, 315–350 x 229–250 µm. The collar is stalked, its rim irregularly incised; the sides of collar bear several sharp longitudinal carinae; the shoulder is low ( Fig. 47 ). The chorion is covered with closely packed hexagonal FCIs; the FCI walls are thin, consisting of shallow furrows; the floors flat with 4-8 small punctations medially ( Fig. 48 ). The row of micropyles is subequatorial; their orifices are small with indistinct lips, some set on micropylar mounds and surrounded by pentagonal rosettes ( Fig. 48 ).

Material examined. Lectotype, male (pinned), D. compacta McLachlan (Dictyopteryx) , [McL. label] / Sibir. orient. (Maa(c)k) / compacta McL. / Dictyopteryx compacta McL. The type-series in BMNH includes three paralectotypes ( Kimmins 1970). Siberia, Eastern Sayan Mountains, Krasnoyarskyi Region, 12 males, 6 females, Bazaikha River, Yenisey R. Basin, 20.05.1959, coll. I. Levanidova. Far East, Prymorskyi Region, 18 males, 10 females, Partisanskaya River, near Frolovka settelment, 29.04.1989, coll. E. Makarchenko.

Distribution. Russia (Siberia, Far East), Mongolia, Japan.

Remarks. The Lectotype of D. compacta is in close agreement with the description of this species by McLachlan (1872). The type of D. compacta is in poor condition, the abdomen fragmented during cleaning, making a study of the internal structure of the epiproct impossible. However, the shape of the hemitergal lobes, lateral stylets present, and the short, blunt, spoon shaped epiproct ( Fig. 40 ) suggests that the species should be transferred to Skwala Ricker 1943 with the valid name Skwala compacta (McLachlan) comb. nov. Skwala pusilla ( Klapálek, 1912) is therefore a subjective junior synonym of Skwala compacta ( McLachlan, 1872) syn. nov.

Figures

FIGURES 39 – 41. Skwala compacta: 39. Habitus (Photograph by M. Tiunov). 40. Type, male abdominal tip, dorsal, pinned. (Photograph by D. Goodger). 41. Same, recent material, dorsal. (Photograph by T. Tiunova).

FIGURES 42 – 45. Skwala compacta: 42. Male abdominal tip and aedeagus, dorsal. 43. Male left hemitergal lobe, dorsal. 44. Cowl: sclerites of the internal basal anchor, lever arm, epiproct, lateral stylet, lateral. 45. Female abdominal tip, ventral. Scale (mm): 43, 44 = 1.0.

FIGURES 46 – 48. Skwala compacta, egg: 46. Habitus lateral. 47. Collar, lateral. 48. Chorion structure, micropylar orifice, mound, and pentagon rosettes, dorsal view.