Mecyclothorax rahimata, Liebherr, James K., 2013

Liebherr, James K., 2013, The Mecyclothorax beetles (Coleoptera, Carabidae, Moriomorphini) of Tahiti, Society Islands, ZooKeys 322, pp. 1-170 : 96-97

79. Mecyclothorax rahimata sp. n.

Diagnosis.

Among the Tahitian Mecyclothorax globosus group species with two supraorbital setae and no dorsal elytral setae - setal formula 2101 (Figs 41A, 42 A–C) - this species is diagnosable by the very large head and narrowly ovate elytra with very shallow, minutely punctate discal striae (Fig. 41A). The head is very broad relative to the pronotum and elytra; MEW/MHW = 1.90. Only Mecyclothorax popotioaoa Liebherr of Moorea (Fig. 41B) shares the same body shape incorporating a large head and narrow hindbody, and given the similarity in setation and microsculpture, the two species are deemed sister species. Standardized body length 3.75 mm. Head broad with small, little convex eyes, ocular ratio 1.42; the ocular lobe broadly convex, little projected from head, eye not covering posterior portion, ocular lobe ratio 0.75; frontal grooves well defined, convergent anteriorly, narrow posteriorly, broad and deep near frontoclypeal suture; antennae moderately elongate, submoniliform, antennomere 8 length 1.75 × maximal breadth. Pronotum not transverse, MPW/PL = 1.08, base narrowly constricted, MPW/BPW = 1.63; lateral margins distinctly convergent anterad right hind angles, then subangularly divergent anteriorly; median base sloped upward to meet convex disc, moderately depressed, 10-11 isolated punctures each side; basal margin broadly convex between hind angles, the angles canted forward due to convexity of margin; anterior transverse impression narrow and shallow, smooth; anterior callosity slightly convex, smooth but with 10-12 very minute longitudinal wrinkles crossing each side; front angles tightly rounded, slightly protruded; lateral marginal depression very narrow, the edge carinate, depression slightly broader inside front angles; laterobasal depression only slightly depressed, surface as punctate as lateral reaches of median base, lateral and basal margins beaded. Elytra narrowly ovate, disc convex medially with sides sloped to near vertical juncture with lateral marginal depression; discal striae 1-6 shallow, the striae appearing very shallow to discontinuous between rounded punctures, stria 7 shallower, smooth; sutural interval coplanar with disc basally, narrowed and slightly upraised apically; discal intervals 2-4 slightly convex; humeri angulate, an upraised ridge that obliquely traverses the elytral base joined to humeral angle; lateral marginal depression narrow, edge upturned basally and beaded anterad subapical sinuation; eighth interval subcarinate laterad stria 7 from subapical sinuation to apex; lateral elytral setae 7 + 6. Microsculpture of vertex an evident transverse mesh, the sculpticells difficult to discern in areas of reflected light; pronotal disc with obsolete transverse mesh visible just outside areas of reflected light, pronotal base with shallow isodiametric mesh between the punctures; elytral discal intervals glossy, microsculpture absent. Coloration of head rufous with a brunneous cast, clypeus and labrum rufoflavous; antennomere 1 flavous, 2-3 rufoflavous, 4-11 rufobrunneous; pronotal disc rufopiceous, base and anterior callosity narrowly rufous; elytral disc rufobrunneous with silvery reflection, slightly darker basally, broadly paler apically; elytral lateral marginal depression narrowly rufoflavous apically; femora and tibiae rufoflavous.

Male genitalia. Aedeagal median lobe very small, about half the length relative to adult body length when compared to aedeagi of species with similarly sized males (Fig. 43A versus Figs 43B, C, E); median shaft nearly as broad as basal bulb, evenly curved; apex not extended beyond ostial opening, the ostial canal therefore incredibly short; apex slightly asymmetrical with tightly rounded tip oriented ventrally; flagellar plate small, length 0.3 × distance from parameral articulations to apex.

Holotype male (MNHN) labeled: French Polynesia: Tahiti Nui / Mt. Marau summit el. 1445 m / 4-IX-2006 lot 04 / 17°36.530'S, 149°31.978'W / beating mixed vegetation on / summit ridge J.K. Liebherr // HOLOTYPE / Mecyclothorax / rahimata / J.K. Liebherr 2013 (black-bordered red label).

Etymology.

The species epithet compounds the Tahitian words rahi, or big, and mata, or face, the name signifying the disproportionately large head in beetles of this species.

Distribution and habitat.

The single specimen was found by beating vegetation on the summit ridge of Mont Marau, 1445 m elevation. The vegetation included low stature, 3-4 m tall Weinmannia and Myrsine , plus Dicranopteris ferns and Cyathea tree ferns. The situation was quite mesic, and the type specimen was the only carabid beetle found.