Enneadesmus obtusidentatus obscurior Borowski, 2017

Borowski, Jerzy & Sławski, Marek, 2017, Bostrichidae (Coleoptera) of Socotra with description of two new subspecies, Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 57, pp. 101-111 : 104-108

Enneadesmus obtusidentatus obscurior Borowski subsp. nov.

( Figs 8–9 )

Published records. GEIS (2015):90 (as Enneadesmus obtusidentatus Lesne, 1899 ; Dixam plateau, Haghier, Noged). Type material. HOLOTYPE: J, labelled: ‘ YEMEN, SOCOTRA ISLAND, Noged plain, Abataro border of sand dunes and shrubland, 12.–13.VI.2012, 12°22.1′N, 54°03.4′E, 20m, Socotra expedition 2012, J. Bezděk, J. Hájek, V. Hula, P. Kment, I. Malenovský, J. Niedobová & L. Purchart leg.’ ( NMPC). PARATYPES: 14 spec. ( NMPC, JBCW), same data as in holotype ; 1 spec., labelled: ‘ SOCOTRA ( YEMEN), Zam Hom , 7.IV.2008, at lamp, leg. A. Carapezza’ ( NMPC) .

Description. Body length 3.2–4.3 mm. Body reddish-brown to dark brown.

Head. Antennae with nine antennomeres; club formed with three terminal antennomeres. Antennomeres III–VI short, together subequal in length to first antennomere of club (i.e. antennomere VII); second and third antennomere of club (i.e. antennomeres VIII and IX) ca. as long as wide. Labrum narrow, transverse, anterior margin with dense brush of golden setae. Epistome at middle produced anteriad, smooth and lustrous, anterior margin shallowly arcuately emarginated; posterior part paler, brownish-red. Basal and lateral parts of epistome setose, setae directed backwards, towards front. Front finely granular, makes a common uniform surface with vertex, only a girdle of long erect golden-yellow setae marking border between them. Vertex granular anteriorly, becoming finely longitudinally rugose at and posteriorly from middle. Eyes large, strongly protruding from outline of head.

Pronotum somewhat wider than long, sides indistinctly rounded and apically strongly tapering anteriad and without lateral carinae. Anterior part of pronotum wrinkled with 6–8 larger, sharply triangular denticles; behind middle pronotum finely granular, granules (very small papillae) sparsely distributed, surface between them smooth and lustrous. Scutellum rectangular, posterior margin straight.

Elytra cylindrical, distinctly truncated posteriorly. Humeral protuberances conspicuous. Elytral punctures in longitudinal rows, laterally and near scutellum confused with additional punctures on intervals. Suture on truncation swollen and elevated above surface. Upper part of truncation with pair of prominent tubercles or denticles, additional tubercle or indistinct, slightly convex transverse crease at middle of sides. Elytral setation yellowish-brown, short, recumbent, somewhat longer and denser posterolaterally.

Coxae, femora and tarsi yellowish-brown, tibiae slightly darker. Outer margins of tibiae with fine denticulation and longer pilosity.

Ventral surface of body brown to dark brown.

Male ( Fig. 8 ). The most characteristic feature differentiating male from female is setation of front: in male long erect setae occur on sides, where they form a distinctive girdle connected on upper and middle part of front; front inside the girdle is filled with short, recumbent setulae directed towards vertex; here surface is smooth and lustrous, finely but rather sparsely granulated. Another important difference make prominent dents and tubercles on elytral truncation: in male in upper part a pair of short, sharply cuneate dents directed backwards and inwards, and on sides of middle part a prominent stump tubercle. Additional male characters are shorter joints of anterior tarsi and lustrous entire surface of truncation.

Female ( Fig. 9 ). In female long erect setae occur as well on sides of front, making there – like in males – a distinctive girdle, as within the girdle; surface of front within the girdle finely but densely granular and apparently rough between granules. Upper part of elytral truncation with pair of short, prominent tubercles bluntly rounded on tips; on sides of middle part transverse, slightly convex crease of indefinite contours. Additionally females differ in having shorter protarsomeres and partly – especially near tubercles and crease – punctured surface of truncation.

Differential diagnosis. Similar to the continental (African and Arabian) E. obtusidentatus obtusidentatus Lesne, 1899 ( Figs 10–11 ), but differs in smaller size (3.5–5.0 mm in E. o. obtusidentatus ), elytral index I=1.6–1.7 (as compared to I=1.8–1.9), and distinctly shorter and less prominent tubercles and denticles on elytral truncation.

Remark. In the genus Enneadesmus Mulsant, 1851 the exact size, shape and position of denticles and tubercles on the truncation of the elytra provide (despite repetitive general pattern) distinctive characters of particular taxa.

Etymology. The Latin adjective meaning obscure.

Geographical element and distribution. Palaearctic element, Socotran endemic.

Figures

Figs 8–13. Habitus in dorsal view. 8–9 – Enneadesmus obtusidentatus obscurior subsp. nov. (8 – male, 9 – female); 10–11 – E. obtusidentatus obtusidentatus Lesne, 1899 (10 – male, 11 – female); 12–13 – E. forficula socotrensis subsp. nov. (12 – male, 13 – female).