Mecyclothorax orbiculus, Liebherr, James K., 2015

Liebherr, James K., 2015, The Mecyclothorax beetles (Coleoptera, Carabidae, Moriomorphini) of Haleakala-, Maui: Keystone of a hyperdiverse Hawaiian radiation, ZooKeys 544, pp. 1-407 : 179-181

Taxon classification Animalia Coleoptera Carabidae

(074) Mecyclothorax orbiculus sp. n. Figs 90E, 94

Diagnosis.

Among the triplet of Mecyclothorax microps group species without dorsal elytral setae, this species stands out due to the subellipsoid elytra, the lateral margins markedly convex from the narrowed humeri to the apex (Fig. 90E). The eyes are more convex than in either of the other species in the triplet, with ocular ratio = 1.38; versus 1.28-1.33 in the other two species. The elytral microsculpture also differs, being a distinct isodiametric mesh versus transverse mesh to transverse lines in the other two species. Setal formula 2 2 0 0. Standardized body length 4.1 mm.

Description

(n = 1). Head capsule with frontal grooves broad, shallow, a broad low convexity laterally before the eye and a very low, rounded carina mesad anterior supraorbital seta; dorsal impression of neck broadly, slightly concave; 14-15 ommatidia across horizontal diameter of eye; labral anterior margin angularly emarginate to 1/6 of labral length; antennae nearly moniliform, antennomeres 2-3 with sparse pelage of short setae; mentum tooth with sides acute, apex pointed. Pronotum slightly transverse, MPW/PL = 1.22, moderately constricted basally, MPW/BPW = 1.49; hind angle obtuse due to convex margin behind angle; lateral margins slightly convergent anterad sharply projected hind angles; median base moderately depressed relative to disc, ~14 punctures each side; basal margin slightly convex between laterobasal depressions; median longitudinal impression finely incised, shallow but evident; anterior transverse impression broad, shallow, obsolete medially; anterior callosity co planar with disc medially, slightly raised laterally, smooth, glossy; front angles slightly projected, tightly rounded; apical pronotal width greater than basal width, APW/BPW = 1.05; lateral marginal depression narrow, the edge beadlike to upturned near broader area at front angle; laterobasal depression with irregular surface, continuous with lateral depression. Proepisternum with 5-6 minute punctures along hind marginal groove; prosternal process broadly depressed medially. Elytra with narrow humeri, basal groove distinctly curved to meet lateral marginal depression at subangulate humerus, MEW/HuW = 1.91; parascutellar striole shallow, with 4 punctures; sutural interval slightly upraised relative to lateral intervals throughout its length; sutural and 2nd striae of subequal depth from base to apex; discal striae 1-6 progressively shallower, stria 7 traceable though interrupted repeatedly; discal striae 1-5 shallowly punctate, minute elongate punctulae in the base of stria 6, all striae smooth and complete on elytral apex; elytral intervals slightly convex medially, nearly flat laterally; 8th interval laterad 7th stria subcarinate, more convex than more mesal intervals; lateral elytral setae arranged in anterior series of 7 setae and posterior series of 6 setae; elytral marginal depression broader, margin slightly upraised at humerus, narrow, beadlike from midlength to subapical sinuation; subapical sinuation shallow, more abruptly incurved anteriorly. Mesepisternum with ~10 punctures in 2-3 rows; metepisternal width to length ratio = 0.72; metepisternum/metepimeron suture distinct. Abdomen with indistinct lateral wrinkles on ventrites 1-3 and circular lateral depressions on ventrites 3-6; suture between ventrites 2 and 3 reduced laterally, effaced; apical female ventrite with 4 equally spaced setae and median trapezoid of 4 subequal, short setae. Legs-metatarsomere 1/metatibial length ratio = 0.19; metatarsomere 4 length along outer lobe 1.3 × medial tarsomere length, apical and subapical setae present; metatarsal dorsolateral sulci broad, basal tarsomeres medially subcarinate. Microsculpture of vertex a shallow isodiametric mesh, transverse sculpticells, breadth 2 × length mesad eyes; pronotal disc with transverse mesh, sculpticell breadth 2 –4× length, median base with mixture of isodiametric and transverse sculpticells, breadth 2 × length; elytral apex with mixture of isodiametric and transverse sculpticells in transverse rows; metasternum with distinct transverse mesh; laterobasal abdominal ventrites with swirling isodiametric and transverse microsculpture. Coloration of vertex rufobrunneous with rufoflavous clypeus; antennomeres 1-3 flavous, 4-11 rufoflavous; pronotal disc rufous with brunneous cast, lateral margins, base, and apex broadly rufoflavous; proepipleuron rufoflavous, proepisternum rufobrunneous; elytral disc rufobrunneous with indistinct purplish sheen, sutural interval rufoflavous basally, flavous in apical 1/3, elytral lateral margin depression, 9th interval and apex rufoflavous; elytral epipleuron flavous dorsally, rufoflavous ventrally, metepisternum rufobrunneous; abdomen with abdominal ventrite 1 rufobrunneous, ventrites 2-3 medially rufopiceous, ventrites 4-6 rufoflavous, with apical half of ventrite 6 flavous; metafemur flavous; metatibia flavous with rufoflavous cast.

Female reproductive tract. The lone female specimen was not dissected.

Holotype.

Female (BPBM) labeled: HI: Maui Is. Haleakala / Waikamoi N.C.P. 1750 m el. / 20°47.21'N, 156°13.82'W / 12-III-2002 R. Takumi / pyr. fog mossy ohia // HOLOTYPE / Mecyclothorax / orbiculus / Liebherr / det. J.K. Liebherr 2015 (black-margined red label).

Etymology.

The species epithet orbiculus is the diminutive of orbis, or circle, and signifies the small eyes characteristic of this species.

Distribution and habitat.

The type specimen of this species was collected at 1750 m elevation within the Honomanu drainage of the Waikamoi Nature Conservancy Preserve (Fig. 94). It was found in moss adhering to an ‘ōhi‘a trunk.