Mechistocerus inornatus, Colonnelli, 2014

Colonnelli, Enzo, 2014, Apionidae, Nanophyidae, Brachyceridae and Curculionidae except Scolytinae (Coleoptera) from Socotra Island, Acta Entomologica Musei Nationalis Pragae 54, pp. 295-422 : 333-336

Mechistocerus inornatus sp. nov.

( Figs 44, 45 )

Type material. HOLOTYPE: J ( NMPC), ‘ Yemen, Socotra Island // Dixam plateau // Firmihin ( Dracaena forest) // 12°28.6′N, 54°01.1′E, 490 m // Jiří Hájek leg. 15-16.xi.2010 ’. PARATYPES: 6 JJ 10 ♀♀, same label data as holotype (12 NMPC, 4 ECRI) ; 1 ♀, ‘ Yemen, Socotra Island // Dixam plateau // Firmihin ( Dracaena forest) // 12°28.6′N, 54°01.1′E, 490 m // L. Purchart leg. 15-16.xi.2010 ’ ( NMPC) ; 1 J 3 ♀♀, ‘ Yemen, Socotra // Dixam plateau Firmihin // ( Dracaena forest) 490 m // 12°28.6′N, 54°01.1′E // 15-16.xi.2010 // P. Hlaváč leg.’ (3 NMPC, 1 ECRI) ; 1 J, same locality and date with indication ‘at light’ ( NMPC) ; 10 JJ 34 ♀♀, ‘ Yemen, Socotra island // Dixam plateau 14-15.vi.2012 // Firmihin, Dracaena woodland // 12°28.6′N, 54°01.1′E, 490 m’, ‘ Socotra expedition 2012 // J. Bezděk, J. Hájek, V. Hula, // P. Kment, I. Malenovský, // J. Niedobová & L. Purchart leg.’ (38 NMPC, 8 ECRI) ; 3 JJ 5 ♀♀, ‘ Yemen, Socotra Island E // Firmihin plato, 400-500 m // N 12°28.46″, E 54°00.89″ // V. Hula & J. Niedobová leg. // 18-19.vi.2010 ’ (6 NMPC, 2 ECRI); 1 J, ‘ Yemen, Socotra Isl. Firmihin, // GPS 12.474N, 54.915E, 530 m // x.2000 // leg. V. Bejček & K. Šťastný’ ( NMPC); 8 JJ 18 ♀♀, ‘ Socotra Is. ( YE) Dixam plateau // Firmihin ( Dracaena forest) // 12°28.6′N, 54°01.1′E, 490 m // Jan Batelka leg. 15-16.xi.2010 ’ (20 JBPC, 6 ECRI); 5 JJ 14 ♀♀, ‘ Yemen, Socotra Island // Firmihin, 400-500 m // N 12°28′27″, E 54°0′54″ // 22-25. vi.2009 // L. Purchart & J. Vybíral lgt.’ (14 NMPC, 2 BMNH, 3 ECRI); 1 ♀, ‘ Yemen, Socotra Island E // Homhil area, 400-510 m // N 12°34.25″, E 54°18′53″ // 9-10.ii.2010, at light // L. Purchart & J. Vybíral lgt.’ ( NMPC); 1 ♀, ‘ Yemen, Socotra Island // Wadi Zirik, 650-670 m // N 12°29′35″, E 53°59′28″ // 16.vi.2009, L. Purchart lgt.’ ( NMPC) ; 6 JJ 5 ♀♀, ‘ Yemen, Socotra Island // Dixam plateau, Wadi Zerig // pools, Juncus marsh ; Dracaena // trees; cave 13-14.vi.2012 // 12°29.6′N, 53°59.5′E, 655 m’, ‘ Socotra expedition 2012 // J. Bezděk, J. Hájek, V. Hula, // P. Kment, I. Malenovský, // J. Niedobová & L. Purchart leg.’ (8 NMPC, 3 ECRI) ; 1 ♀, ‘ Yemen, Socotra Island // Al Haghier Mts. // wadi Madar, 1180-1230 m // 12°33.2′N, 54°00.4′E // Jiří Hájek leg. 12-14.xi.2010 ’ ( NMPC) ; 1 ♀, ‘ Yemen, Socotra Isl. , Zerik, // 25-27.iii.2001, // leg. V. Bejček & K. Šťastný’, ( NMPC) ; 1 J 1 ♀, ‘ Socotra ( YE) // Thar (pitfall trap) // 5.III.2008 - R. Sindaco leg.’ ( MCCI) .

Description. Male holotype. Body length 13.5 mm. Brown, apex of femora, tarsi and antennal club pitchy-brown, moderately shining. Dorsal vestiture of moderately dense, pale ochreous to brownish, recumbent, roundish to elliptically elongate striate scales, pale ones forming two longitudinal stripes on both sides of pronotal disc and more condensed on sides of elytra although not forming a definite pattern. Scutellum densely covered by pale ochreous scales. Some erect, rather elongate scales are on elytral declivity and near apex. Ventral side clothed with dense, pale, yellowish, recumbent, shortly elliptical scales, which are more elongate on sides of urosternites and hair-like towards middle of them ( Fig. 44 ).

Head. Rostrum as long as pronotum, regularly curved, finely and sparsely punctured, faintly carinate on basal fifth, dilated at base and here with some pale erect elongate scales, slightly widening towards apex. Antennae inserted at middle of rostrum; scape thin and moderately clubbed; funicular antennomere I thicker and shorter than antennomere II, this more than 3 times as long as wide, antennomeres III to VII becoming gradually shorter, antennomere VII not transverse; club fusiform-elongate, setose and about as long as preceding four antennomeres. Head globose, not continuing curve of rostrum; space between eyes narrower than dilated base of rostrum and with elongate pit. Eyes large and not protruding from head convexity, dorsally surrounded by yellowish quite elongate recumbent scales.

Pronotum 0.87 times as long as wide, with faintly rounded subparallel sides up to apical third, then rapidly narrowing and slightly sinuate towards apical margin which is rounded, with weak incision in middle, and protruding over vertex of head; base bisinuous; disc feebly convex, with coarse and very dense reticulate punctures, and with hardly visible median smooth bare line. Scutellum rounded, convex.

Elytra 1.73 times longer than wide, disc almost flat and with deep scutellar depression, maximum width at apical quarter; sides almost straight and barely diverging from moderately protruding humeri up to apical quarter and then quite strongly jointly curved towards apex; preapical calli moderate but enhanced by impression situated in front and behind them. Striae formed by slightly elongate rectangular quite shallow punctures bearing recumbent scale and separated each other by distance about equal to their diameter. Interstriae slightly wider than striae, almost flat, with fine confuse punctures.

Legs robust; femora quite strongly clubbed and compressed at base, profemora with barely visible tooth, meso- and metafemora toothed, teeth of metafemora strong and acute with extreme apex blunt, moderately and rather uniformly clothed by recumbent ochreous scales and by semierect elongate ones on dorsal margin; tibiae relatively elongate, curved at apex, internal margin sinuous; tarsi relatively stout, clothed by dense hair-like yellowish scales, claws divergent, simple.

Ventral side. Metaventrite depressed and sulcate at middle and with tooth-like tubercle over metacoxae; abdominal ventrites I and II and metaventrite forming large common median depression.

Variability. The species, like several others of its genus, is quite variable, both in size and body shape. Females differ from males by their longer rostrum, up to 1.07 times as long as pronotum, elytra more uniformly convex, parallel sided and more elongate, up to 1.85 times longer than wide, preapical calli weaker, femora less strongly clubbed, abdomen lacking impressions, and metaventral tubercle weak and only slightly protruding over the metacoxae. Depending on the freshness of the specimens, their vestiture may be more or less dense. Also body shape is variable, sides of prothorax being more or less rounded, and sometimes more converging from base to apical third, and elytra of some specimens wider than those of the holotype.

Male genitalia. Aedeagus as depicted in Fig. 45 .

Body length 7.4–14.0 mm, being almost all specimens above 10.5 mm.

Differential diagnosis. Among some 150 species of Mechistocerus Fauvel, 1863 distributed from Australia across the Oriental and Afrotropical Regions, only a few have rather uniform vestiture and large size. The new species can be compared only with M. breviusculus Hustache, 1932 from Congo and Togo which is immediately distinguished by its shining bare granules on elytra, and erect scales of the underside ( HUSTACHE 1932, MARSHALL 1958). On the other hand M. brevicornis Hustache, 1932 from Zanzibar has carinate and basally sulcate rostrum, second funicular antennomere as long as the first, and anterior half of scutellum devoid of scales ( HUSTACHE 1932), and cannot be confused with the new species. Mechistocerus trapezithorax Hustache, 1929 from Kilimanjaro has a vaguely spotted vestiture without pronotal stripes, shorter antennae, elytral striae with ocellate punctures separated by a distance much greater than their diameter and tibiae with a blackish ring ( HUSTACHE 1929). None of the Madagascan or the other African Mechistocerus , or the several species from the Oriental and the Australian Region, can be confused with M. inornatus sp. nov.

It is worth pointing out differences between Mechistocerus and related taxa, namely Rhadinomerus Faust, 1892 (both genera comprise several species very different from each other) are far from unequivocal ( HELLER 1937) and are based on variable characters, like femora more or less strongly clubbed, kind of vestiture of base of femora, and level of the posterior ending of rostral channel which evidently depends on the length of rostrum. As a proof of this, among the Madagascan species only Rhadinomerus longulus ( Fairmaire, 1903) , which according to HUSTACHE (1924) could be somewhat similar to the Socotran Mechistocerus , was included in Mechistocerus by HUSTACHE (1924), and then moved into Rhadinomerus without comment by the same author ( HUSTACHE 1936a). Rhadinomerus longulus differs from M. inornatus , apart from by the small size (7.0–8.0 mm), by its first funicular antennomere much wider than the following ones, small interocular pit, keeled pronotum, setose pronotal punctures, reddish markings on elytra ( FAIRMAIRE 1903, HUSTACHE 1924). Mechistocerus inornatus sp. nov. was illustrated by WRANIK (2003: plate 178, fig. g) as ‘ Curculionidae , not yet identified’.

Etymology. The species name, the Latin adjective inornatus (- a, - um), meaning ‘inornate, plain’ was chosen in reference to the dorsal vestiture of the new species which is rather uniform compared to that of most of the remaining species of Mechistocerus .

Collection circumstances. The majority of specimens from Firmihin were attracted to a light trap put in Dracaena cinnabari woodland with small trees of Croton socotranus Balf. f. and Jatropha unicostata Balf. f. (both Euphorbiaceae ); several specimens were found at night, crawling on freshly fallen Dracaena cinnabari trunks (J. Hájek, pers. comm).

Distribution. Endemic to Socotra Island.

Figures

Figs 40–47. 40, 42 – Mesoxenomorphus rugipennis sp. nov.: 40 – habitus of the holotype; 42 – aedeagus of a paratype in dorsal view. 41 – Mesoxenomorphus africanus Wollaston, 1873 from South Africa, Port Elizabeth, habitus. 44–45 – Mechistocerus inornatus sp. nov. 44 – habitus of the holotype; 45 – aedeagus of a paratype in dorsal view. 43, 46 – Sibinia caldaraedicata sp. nov.: 43 – aedeagus of a paratype in ventral view; 46 – habitus of the holotype.