Stenus melanopus (Marsham, 1802)

Ryvkin, Alexandr B., 2012, New species and records of Stenus (Nestus) of the canaliculatus group, with the erection of a new species group (Insecta: Coleoptera: Staphylinidae: Steninae), European Journal of Taxonomy 13, pp. 1-62 : 43-44

Definition of the melanopus group

Diagnosis

Body size moderate; body length of only known species: 2.8 to 3.7 mm.

Head rather small in comparison to elytra and pronotum. Upper surface between eyes bisulcate, with longitudinal elevations and impressions well developed. Labrum with anterior margin straight, neither sinuate nor notched. Internal tooth of each mandible placed much more distally than middle, turned evidently dorsally of the main plane. Maxillar palpi with basal segment yellow and not shortened. Prementum of normal length, not reduced. Antennae fairly short, with penultimate club segments globular to slightly transverse, the last segment a bit longer than broad.

Pronotum with sharp longitudinal median furrow, rather broad and deep in basal half, vague or vanishing before the middle.

Elytra moderately long, slightly trapezoid with humeri developed.

Legs moderately long; segment 4 of tarsi without emargination; segment 1 of metatarsi a bit shorter than segment 5, distinctly shorter than segments 2 to 4 together.

Abdomen moderately convex, with paratergites evident on abdominal segments 3 to 7; four anterior visible tergites with four short but evident longitudinal keels at basal part each; posterior margin of tergite 7 with well developed, fine membranous fringe.

Puncturation of pronotum and elytra moderate, non-rugose, with interstices fairly flat.

Ground sculpture entirely absent, upper surface varnish shining.

Pubescence moderate, contiguous.

MALE. Legs without specific features; posterior margin of abdominal sternites 6–7 about straight; abdominal sternite 8 with broad and very shallow, rounded emargination of posterior margin, without evident depression; abdominal sternite 9 with posterolateral teeth very short, not incurved inwards. Aedeagus relatively small; median lobe archetypically lanceolate, with apical sclerotized part angularly rounded; endophallus with paired medial bands and unpaired bar distinct in middle, with very small but visible lateral parts, and with H-shaped expulsion clasp producing fairly broad lateral portions; basal tube evidently sclerotized. Parameres cylindrical, without apical broadening; apico-internal setiferous surface poorly differentiated, setae rather uniform.

FEMALE. Posterior margin of abdominal sternite 8 obtuse-angularly rounded; each valvifer with very short posterolateral tooth, backwards directed. Spermatheca sclerotized.

In the structure of the mandibles, the abdominal tergites, the male genitalia and abdominal sternite 9 of both males and females (valvifera), the melanopus group is most closely related to the atratulus - fuscipes -cautus -crassus complex. It differs from all the species of this complex by the presence of a long and sharp, longitudinal median furrow on the pronotum, as well as by the posterolateral teeth of abdominal sternite 9 of both males and females, which are very short and not incurved inwards.

Taxa included

S. (N.) melanopus ( Marsham, 1802) .

Bionomics

See below.

General distribution

See below.