Megarcys teslenkonis, Zwick, 2010

Zwick, Peter, 2010, New Species And New Records Of Plecoptera From Korea And The Russian Far East, Illiesia 6 (9), pp. 75-97 : 93-94

Megarcys teslenkonis sp. n.

(Figs. 47-51)

Material examined. ♀ Holotype, REPUBLIC OF KOREA: Chungbuk, Sangchon-Myeon, Dungeon-li near Doma Pass, Alt. 750 m, 2.-26.V. 2006, 2 Malaise traps in forest on small stream; 2 eggs recovered from the abdomen were slide mounted. Adult habitus. Slightly brachypterous, FWL 20 mm, BL 18 mm. Dorsal face and sides of body very dark brown. There is a yellow head pattern and a yellow median band on the pronotum (Fig. 47). Mesonotum with yellow patch in middle, middle of metathorax and of first two abdominal tergites medially also lighter than remaining dorsal surface. Ventral side mainly yellow, thoracic sternites light ochre. Antennae and cerci almost black. Femora dorsally brown, ventrally light brown, with yellow knee ring. Light brown patches in the basal part of front and rear face of femur grow successively larger from front- to hind-leg where they occupy about 2/3 of the total length. Tibiae dark brown from base to subgenual organ, then abruptly yellow but grading again to dark brown towards tip. Tarsal segment 1 lighter brown than 2 and 3.

Submental gill a short slender cone, gill on lower front corner of pronotum also small. The curved downhanging lateral single gills at the front of meso-and metathorax are larger, about as long as in M. ochracea , but not as thick.

Male. Not known.

Female. The yellow S8 forms a rounded slightly convex subgenital plate ending in two long lobes extending over half of S9 (Fig. 48). The medial gap separating the lobes is anteriorly heart-shaped, caudally approximately parallel. At the level of the S9 hind margin each lobe is on the outside constricted and then strongly expanded so that a prominent lateral lobe is formed from where the convex contour curves regularly towards the median gap.

Egg. Large, 400 µm long. Quadrilateral with flat opercular area, in side view (Fig. 49) resembling a cube to one side of which is attached a short pyramid supporting the collar. Each side of the cube and of the pyramid is distinctly concave. In oblique views (Fig. 51), the egg therefore appears to be of some irregular shape. The collar appears double, the shorter outer and the longer and narrower inner ring both ending in a number of pearls or short fingers (Fig. 50). Chorion with hexagonal follicle cell impressions. The limits between cells are corrugated and a bit raised, at high magnifications the egg contour appears rough. Opercular line, micropyles, and anchor not observed.

Diagnosis. The subgenital plate with its large lobes resembles M. magnilobus Zhiltzova, 1988 from the Russian Far East, the west-nearctic M. signata (Hagen, 1874) , and Sopkalia yamadae ( Okamoto, 1917) from Japan. In S. yamadae (which was compared) the gap separating the lobes of the subgenital plate is also heart-shaped but is wider. None of the similar species possesses outwardly directed angles at the base of each lobe ( Okamoto 1917, Ricker 1952, Van Wieren et al. 2001, Zhiltzova 1988, Teslenko & Zhiltzova 2009), and all differ in pigmentation and pattern of the fore body. Known Megarcys eggs ( van Wieren et al. 2001, and my own observations of M. ochracea (Klap{lek, 1912) and also the egg of S. yamadae ( Isobe 1988) have a double collar. Several have a somewhat battered appearance because of concave areas on the egg surface. However, M. teslenkonis is the only species with a flat-topped quadrilateral egg.

Etymology. This large beautiful species is dedicated in friendship to Valentina Teslenko (Vladivostok) who contributed importantly to the knowledge of stoneflies of the East Palearctic region. The name is treated like a Latin noun of the O-declension, in the genitive case.

Nomenclatural note. When checking the descriptions of additional nominal Asian species of genus Megarcys ( Illies 1966) the correct original spelling of one name was found to be Megarcys lepneva (Š{mal, 1939), not lepnevae as used in the literature. Š{mal spelled lepneva both in the description and the figure legend, the spelling was clearly not a lapse.