Leuctra simplex Zhiltzova, 1960

Teslenko, Valentina A. & Palatov, Dmitry M., 2019, A new micropterous winter species of Leuctra (Plecoptera: Leuctridae) and little known endemic stoneflies from the Greater Caucasus, Zootaxa 4613 (2), pp. 342-354 : 347-349

Leuctra simplex Zhiltzova, 1960

Material examined: 4♂, 7 larvae. Russia. Krasnodarky Region , Novorossiysk District , Abrau-Dyurso Distric , Abrau River, 2 km above the Abrau Settlement, 155 m .a.s.l., 44°43.546 N 37°35.498 E, 18.0 4.2018, coll. D. Palatov.

Structure of the male genitalia of L. simplex agrees well with original description ( Zhiltzova 1960), except for a color details. The general color is brown with contrasting yellow patches. Head tinted chocolate brown with dark tentorial callosities at the base of the antenna and small dark spot in the area of the anterior ocellus; occiput covered with dark brown callosities posteriorly. Antenna dark brown, except flagellular segments 1–4 pale-yellow; scape and pedicel dark brown ( Fig. 16 ). Pronotum light brown with dark brown callosities. Scutum of meso- and metanotum light brown with a diffuse dark brown patch above scutellum. Legs are striped, femur yellow with mesal diffuse dark brown patch ( Fig. 16 ).

Mature larvae. The association of the mature larvae with adults was established from preemergent male larvae, collected together with adults. Body length: 4.7–5.4 mm in males, 5.9–6.0 mm in females. General color brownish with greenish tint ( Fig. 17 ). On the head each ocellus contoured with a thin bright brown stripe of chocolate brown tint; a narrow brown band between lateral ocelli above epicranial suture ( Fig. 17 ). Clypeus typical with a pair of small dark patches on corners. Antenna, legs and cerci pale. Pronotum oval, approximately 1.6Χ wider than long, without pattern, anterior and posterior margins slightly darker than disk ( Fig. 17 ). Rear edge of thorax between front wing-pads rounded; between hind wing-pads the thorax margin forms two little pointed extensions ( Fig. 17 ). Fore femur 2.2Χ longer than wide ( Fig. 22 ). Abdominal terga I–VI greenish brown, integument pale, matte in appear- ance, terga VII–X pale ( Fig. 17 ).

Setation. Macroscopic pilosity sparse. Head bears a few short club-shaped bristles behind the eyes. Antennal segments with pointed setae much shorter than length of segments. Setal fringe of short club-shaped bristles with rounded apices and a few occasional long, fine hairs on pronotum only on anterior corners ( Figs 18, 19 ); one or two short bristles are on posterior pronotal margin closer to the posterior corner. Occasional long hairs and tiny clothing hairs cover pronotal disk ( Fig. 19 ). Setation of legs is mixed: setal fringe on the outer femur margin of fore leg includes a few scattered, short acute bristles and a few long, fine hairs in second half of outer margin ( Fig. 22 ). The longest acute bristles not exceed 10% of femur width on the fore leg. Tibia with spine-shaped bristles in distal half; outer margin with a few fine hairs ( Fig. 22 ). Outer margin of femur of hind leg with sparse, cylindrical bristles and long fine hairs; setae on the tibia are similar with those on fore leg ( Figs. 22, 23 ). Wing pad margins without pilosity. All terga covered with tiny clothing hairs and with a posterior fringe of short, thin setae ( Fig. 20 ). Tergum IX of male additionally covered with stiff acute bristles posterolaterally ( Fig. 21 ). Tergum X with numerous similar stiff bristles distributed evenly over tergum, and longer than that on tergum IX, especially along posterior margin ( Fig. 21 ); the longest bristles not exceed 10% of tergum X width. Cerci with 10–12 slender acute bristles in the apical whorl on basal cercal segments, length of bristles does not exceed the segment length ( Fig. 21 ). Paraprocts of male covered with stiff acute bristles near posterior edge ventrally.

Diagnosis. Mature larvae have a contrast thin, bright brown stripe around each ocellus and narrow, brown band between lateral ocelli on the head. Rear edge of mesonota between wing-pads rounded; in metanota forming two small pointed extensions. Pilosity sparse. Pronotal fringe at anterior corners as unnumerous, short, club-shaped bristles, rounded at the apex, with a few occasional long, fine hairs.

Remark. The specific identifications of larvae stages in Leuctra , a large and difficult genus remains problematic with exception for a few European species ( Zwick 2004). Using the concept of Operational Taxonomic Units as presented by P. Zwick (2004), the larvae of L. simplex are most similar to those of the prima–hippopus–inermis group and cannot be currently distinguished from the other taxa.

Distribution. The Abrau River, a small foothill river, originates on the western slope of Zhen-Gora Mountain (Abrau Mountains) and flows into Abrau Lake. A rare species, endemic to the western Caucasus and the Krasnodarsky Region occurs at 600 m. a.s.l., adults emerge in May.

Figures

FIGURES 16–17. Leuctra simplex, habitus, male, dorsal. 16. Adult. 17. Larva.

FIGURES 18–23. Larva of Leuctra simplex. 18. Short club-shaped bristles on anterior corner of pronotum. 19. Setae on disk and setal fringe of right anterior corner of pronotum. 20. Terga V–VI with posterior fringe of short, thin setae. 21. Terga IX–X with stiff acute bristles. 22. Right fore leg. 23. Right hind leg.