Cryptarcha solomonensis, Lasoń & Kirejtshuk, 2020

Lasoń, A. & Kirejtshuk, A. G., 2020, A new species of the genus Cryptarcha (Coleoptera: Nitidulidae) from Solomon Islands, Zoosystematica Rossica (China) 29 (2), pp. 323-327 : 324-327

Cryptarcha solomonensis sp. nov.

( Figs 1–6)

Holotype. Male. “ Solomon Islands, Honiara, 80– 250 m, Guadalcanal ld.; Lunga river , 10 km S of Barana, 20.XI–15.XII.2013, Jákl S.” ( USMB).

Paratypes. 3 males ( ALBC, NMP, ZIN) and 1 female ( ALBC) with the same labels as the holotype .

Description of male (holotype). Length 4.1, width 1.8, height 0.5 mm. Moderately convex dorsally and subdepressed ventrally; dorsum mat, dark brown with reddish spots on elytra and with lighter (up to reddish) anterior part of head, pronotal sides, exposed part of abdomen and appendages; underside bright reddish, moderately shining; dorsum with moderately dense and moderately conspicuous yellowish hairs on light parts and with dark hairs on dark parts; hairs markedly longer than distance between their roots and of two kinds: longer ones intermixed with shorter ones; longer hairs forming seven longitudinal rows on elytra; pygidium with rather short and conspicuous yellowish hairs; underside with finer, shorter and less conspicuous hairs than those on dorsum.

Head and pronotum with punctures, somewhat finer than eye facets, interspaces between them about one puncture diameter or greater, vaguely microreticulated to alutaceous. Elytra diffusely covered with rather dense punctures about as fine as those on head and pronotum, but somewhat dense, interspaces between punctures vaguely microreticulated to alutaceous. Surface of pygidium shagreened and dull, covered with short subrecumbent hairs. Ventrites with dense and shallow punctures, interspaces between punctures finely microreticulated to alutaceous. Thoracic underside sclerites with shallower and sparser punctures than those on dorsum, interspaces between punctures more or less smoothed and with slight shine.

Head about as long as distance between eyes, weakly and gently convex, its anterior edge subtruncate to shallowly emarginate; lobes over antennal insertions well raised. Mandibles strongly exposed from under frons and strongly asymmetric; left one markedly longer, thinner and more gently curved than right one; their apices with one weak subapical tooth.

Antennae comparatively short, about twothirds as long as distance between eyes; their club three-segmented and comprising two-sevenths of total antennal length, elongate and more than one and half times as long as wide; antennomere 3 markedly shorter than scape and somewhat longer than antennomere 2 (pedicel). Pronotum widely transverse, rather convex, with evenly sloping sides to narrowly bordered lateral edges; anterior edge moderately bisinuate; sides about one-third as widely subexplanate as antennal club wide;anterior angles moderately projecting anteriorly; posterior edge bi-emarginate and narrowly bordered; posterior angles slightly projecting posteriorly. Elytra evenly vaulted on disk and moderately steeply sloping to very narrowly explanate sides, with adsutural lines visible in distal three-fifths; their apices oblique, separately rounded and forming small sutural angle. Scutellum somewhat transverse, subsemicircular and with rounded apex. Pygidium transverse, its surface subflattened at subtruncate to shallowly emarginate apex.

Antennal grooves distinctly outlined, subrectilinearly and strongly convergent behind mentum. Gular processes comparatively wide and rather strongly curved. Mentum subhexagonal, more than four times as wide as long. Terminal maxillary palpomere subcylindrical and about three and half times as long as wide. Terminal labial palpomere subcylindrical and about twice as long as wide. Prostenal process almost flat and slightly widened before widely rounded and finely bordered apex. Distance between mesocoxae one and half times and that between metacoxae about three times as great as distance between procoxae. Mesoventrite flat in distal half and flatly sloping under prosternal process. Metaventrite medially subflattened, with clear discrimen in distal twothirds; its posterior edge between metacoxae rath- er shallowly emarginate. Postcoxal lines behind meso- and metacoxal cavities following closely posterior edge of coxal cavities. Male anal sclerite slightly exposed from under ultimate abdominal segment. Epipleura at base somewhat wider than antennal club and moderately elevated outwards.

Tibiae subtriangular and slightly narrower than antennal club, protibia with moderately projecting outer subapical angles, meso- and metatibiae with dense rows of short setae at outer edge, spur moderately long and moderately thin. Femora of usual shape and with evenly convex anterior and posterior edges; profemur about twice, mesofemur two and one third, metafemur nearly three times as wide as corresponding tibiae. Tarsi moderately lobed, about a half as wide as corresponding tibiae, with moderately long simple claws.

Aedeagus moderately sclerotised, moderately long (0.5 mm) and not curved. Penis trunk with subacute apex and very long apical orifice; lobes of orifice about a half as long as entire length of penis trunk. Tegmen somewhat longer than penis trunk and bearing long setae at apex.

Female. Sexual dimorphism is expressed in the less asymmetric development of the mandibles and elytral apices slightly projecting and subacute (but not separately rounded as in males). The female protarsi are somewhat narrower than those in males. The ovipositor is moderately sclerotised and moderately long (0.75 mm).

Variation. Length 3.2–4.1 mm. Some variability is observed in the colouration and particularly in outlines of yellow spots on elytra, and also in the sculpture on integument (punctation and reticulation).

Diagnosis. Cryptarcha solomonensis sp. nov. belongs to the strigata -group ( Kirejtshuk, 1987b), which is characterised by light zigzag pattern on elytra. The new species is similar to C. australis Reitter, 1873 (widely distributed in Australia and Tasmania), but distinct from it in the somewhat slenderer body with the yellow colouration on the elytra not reaching presutural parts in their anterior half, the longer and narrower aedeagus having a brush of setae at the apex of the tegmen (but not a pair of paramedian brushes at the apex of the tegmen as characteristic of C. australis ) and the different structure of its ovipositor. From other species of the strigata -group, C. solomonensis sp. nov. is distinguished by the well expressed pubescence and less shining body integument, different pattern of the yellow colouration on the elytra and peculiar structure of the aedeagus. It additionally differs from species of this group in the following characters: from C. elleipsis Kirejtshuk, 1987 ( Australia: Queensland), in the larger body, finer dorsal punctation, wider prosternal process somewhat widened apically, mentum with the anterior angles not projecting anteriorly and elytral epipleura not sloping downwards; from C. minima (Sharp, 1886) ( New Zealand), in the shorter adsutural elytral lines (reaching only about the elytral midlength), pronotal and elytral sides not narrowly explanate, and pygidium mostly covered by the elytral apices; from C. nitida Reitter, 1877 (South Australia), in the somewhat wider body with finer and sparser dorsal punctation, absence of the basal border of pronotum, longer adsutural lines on elytra, and elytral epipleura not sloping downwards; from C. nitidissima Reitter, 1873 ( Australia: Queensland and New South Wales), in the markedly slenderer, larger and not very convex body with much denser dorsal punctation, longer adsutural elytral lines, and narrower antennal club; from C. subnitida Kirejtshuk 1987 (widespread in Australia), in the body not regularly ellipsoid and with denser dorsal punctation, pronotal and elytral sides not narrowly explanate, and also in the elytral apices of both sexes not so extended and leaving pygidial apex somewhat exposed.

Etymology. The species name is formed from the name of the type locality ( Solomon Islands).