Filchneria balcarica Balinsky, 1950

Teslenko, Valentina A. & Palatov, Dmitry M., 2023, Redescription of a few Filchneria Klapálek, 1908 (Plecoptera, Perlodidae) species on the type and fresh material, Zootaxa 5277 (2), pp. 287-312 : 288-292

Filchneria balcarica Balinsky, 1950

Figs. 1–15

Balinsky, 1950: 60, 61, 63, figs 1a–c. Type material contains two females and has been deposited in the Zoological Museum, Warsaw, Poland. Illies, 1966: 359; Zhiltzova, 1971: 1038‒1039, figs. 3 (1‒4); Zwick, 1973: 229, 235; Cherchesova, 2006: 6; Teslenko & Zhiltzova, 2009: 23‒24, figs. 98–101.

Diagnosis. The male of F. balcarica is distinguished by a slightly elevated posterior margin of the tergum 10 that is truncated and straight dorsomedially, its posterolateral edges rounded; large pyramidal paraprocts; and a heavily sclerotized paraproctal sclerite with membranous protrusions at the apex and along the inner edge. The eversible paraproct lobe (EPL), as everted from live material, looks like two rounded membranous swellings covered with tiny sensory spines. Females of F. balcarica differ in the large, wide, and bilobed subgenital plate with deep, Ushaped notch; lobes are widely spaced, rounded and directed inward. The egg is unique, large, and has parallel lateral margins before the transverse ridge. The posterior pole is truncated and medially depressed. The collar is almost unnoticeable, its anchor plate flat, pan-shaped, and pulled inward. The chorionic surface is rough with numerous, raised, large rounded tubercles, densely arranged on the longitudinal ridges. The micropyles, located near equatorially, have lipped orifices.

Complementary description. Male. The original description of the species was carried out on the female ( Balinsky 1950), the male was described later ( Zhiltzova 1971). The overall coloration is similar to that of the female, the male significantly smaller than female, body length 14.5–19.7 mm in (n=2); brachypterous, wings not exceeding tergum 3 ( Figs. 1–4 ). Abdomen dark brown, terga 1‒7 with an indistinct longitudinal medial brown band delimited by pair of narrow, pale bands laterally ( Figs. 1 , 5 ). Terga 5–8 humped laterally. Tergum 8 with a pale membranous longitudinal stripe medially and two submedial swellings densely covered by sensilla basiconica and colorless hairs posterolaterally. Tergum 9 is half hidden under tergum 8; anterior margin and narrow stripe medially is dark, posterior half with pale swelling, covered by sensilla basiconica and colorless hairs posterolaterally ( Fig. 5 ). In caudal view, posterior margin of tergum 10 is weakly elevated, directed forward and upward; in the dorsal view, the posterior margin truncated and straight medially; the posterolateral edges rounded, covered with oval patches of sensilla basiconica which are connected along posteromedial edge, occupying the posterior half of the tergum 10 length ( Figs. 5–8 ). At rest, the paraproct is pyramid-shaped with a rounded tip, inner plane of paraproct weakly sclerotized ( Fig. 7 ). Paraproctal sclerite large, heavily sclerotized dorsally and basally, except apex and inner edge which bears a membranous notch in the middle ( Fig. 7 ). The EPL enlarges into two rounded membranous swellings covered with tiny sensory spines ( Figs. 5, 8 ).

Female. Body length 18.2‒19.5; macropterous ( Fig. 1 ), length of wings 19.3‒20.7 mm (n=2). Sterna 6‒7 are pale with pair of rounded brown spots laterally and brown band anteriorly, slightly widened anterolaterally. Sternum 8 pale with pair of rounded brown spots laterally and a pair of oblique dark brown lateral sclerites which surround subgenital plate anterolaterally ( Fig. 9 ); a paired small brown lateral spots at the base of the subgenital plate closely to posterior margin of sternum 8. Subgenital plate bilobed ( Fig. 9 ), wide and large, occupies 4/5 of the sternum 8 width and half of the sternum 9 lengths, or covers sternum 9 completely. Notch of the subgenital plate is deep and wide, U-shaped arcuate with paired obtuse angles along inner edge distally divides the subgenital plate into two lateral lobes rounded posteriorly and directed inward, one female has darkened lobes. Sternum 9 pale medially, under the lobes of the subgenital plate brownish. Abdominal sternum 10 is pale.

Egg. Ultrastructure is species specific. Relatively large, trilateral in cross-section with dimensions of 619×442 μm. Flat longitudinal ridges delimit the three sides of the egg; each side has additionally a transverse ridge close to the anterior pole ( Figs. 10, 11 ). Egg has almost parallel lateral margins before the transverse ridge, posterior pole truncated, straight, and medially depressed ( Figs. 10, 11 ). The collar is unnoticeable, pedicel short and thin ( Figs. 10, 12 ). The anchor plate flat, pan-shaped, is pulled inward and covered with single globular bodies except for the center ( Figs. 11–13 ). Large globular bodies gathered on the shoulder surface around outer edge of the anchor plate ( Fig. 12 ). The chorionic surface is rough with numerous, raised, relatively large rounded tubercles, densely arranged on the longitudinal ridges ( Figs. 10, 11, 15 ). A transverse row of six micropyles located almost equatorial; micropyles have a lipped orifices; the micropyles height is equal to or slightly exceeds the height of the chorionic tubercles ( Figs. 10, 11, 14 ).

Material examined. 1 male, Georgia, Svanetia, Enguri River , source, 3.08.1957, coll. LA Zhiltzova ( ZIN) ; 1 male, Georgia, Mentrel Ridge, Tekрuri River , altitude 2300 m above sea level, 1.04.1989, coll. A. Koval ; 1 female, Abkhazia, Avadkhara River , a left branch near its headwaters, 14.07.1958, collector unknown ( ZIN) ; 1 female, Russia, North Ossetia, Tseiskiy Ridge, Tseidon River , the left source, higher than the glacier, N 42°77.5297’, E 43°85.568’, 24.07.2021, coll. DMP ( VLA) .

Ecology and distribution. Filchneria balcarica was recently found in the headwaters of glacier-fed stream at 2300 m above sea level, the water temperature being 5°C and the velocity ranging from 0.4‒ 1 m /s. Bottom substrates consisted of cobbles and gravel. This relatively rare species is limited to North-West Caucasus and occurs in Georgia, Abkhazia, Kabardino-Balkaria , and the Republic of North Ossetia-Alania. It inhabits various mountain water courses from rivers to small streams. The emergence period is prolonged, occurring from April-August .

Figures

FIGURES 1–4. Filchneria balcarica Balinsky, 1950 from Caucasus: Abkhazia, Avadkhara River; Georgia, Svanetia, Enguri River and Tekрuri River, Mentrel Ridge. 1. Habitus, female, dorsal. 2. Same of male. 3. Head and pronotum of female. 4. Same of male.

FIGURES 5–9. Filchneria balcarica: Balinsky, 1950 from Caucasus: Georgia, Svanetia, Enguri River; Tekрuri River, Mentrel Ridge;Abkhazia,Avadkhara River.5. Male abdominal tip, dorsal.6. Tergum 10 with chaetotaxy,dorsal.7. Paraprocts, not everted, caudal. 8. Left everted eversible paraproct lobe of male, caudal. 9. Female abdominal tip with subgenital plate, ventral.

FIGURES 10–15. Filchneria balcarica Balinsky, 1950, egg: 10. Longitudinal and transverse ridges, without anchor plate, lateral. 11. Same, with flat, pan-shaped anchor plate. 12. Posterior pole without/with anchor plate, dorsal. 13. Posterior pole with anchor plate covered with globular bodies, lateral. 14. Chorion structure, row of micropyles with lipped orifices. 15. Chorion surface with raised, rounded tubercles.