Mecyclothorax nanunctus, 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 : 286-289

Taxon classification Animalia Coleoptera Carabidae

(113) Mecyclothorax nanunctus sp. n. Figs 149D, 153 D–J, 154B, 155B, 157

Diagnosis.

This species (Fig. 149D) can be separated from all other Mecyclothorax palustris group species based on: 1, uniformly pale body coloration without contrasted elytral lateral margins; 2, presence of two dorsal elytral setae, setal formula 2 1 2 0; and 3, relatively small size; standardized body length 3.9-4.6 mm. Were it to be confused with any other Haleakalā Mecyclothorax , the best candidate for confusion would be Mecyclothorax mauiae (Fig. 68A), as beetles of both species are pale bodied, and the size ranges overlap. Careful attention must be paid to the comparative depth of the sutural and 2nd striae, as this is a major criterion for group membership. Also, the bodies of Mecyclothorax mauiae are broader, with the elytra slightly obovoid; i.e. with the greatest breadth in the anterior half. Conversely Mecyclothorax nanunctus beetles have the elytra more ovoid, with the greatest width in the apical half. The pronotum in Mecyclothorax mauiae is less transverse, though not diagnostically so, and the pronotal lateral depression is narrower with a less explanate margin. The surest arbiter given a male in the series is the male aedeagal median lobe, which in Mecyclothorax nanunctus males is gracile and elongate (Fig. 153 D–J), and in Mecyclothorax mauiae males is short with a broadly rounded apex (Fig. 69). The two species are broadly sympatric (Figs 71, 157), but based on ecological records from the Waikamoi area, Mecyclothorax nanunctus is a species more at home in mesic forest situations dominated by Acacia koa and ‘ōhi‘a ( Metrosideros polymorpha ), whereas Mecyclothorax mauiae is found in wet forest situations that are dominated by ‘ōhi‘a but which also include 'ōlapa ( Cheirodendron trigynum ).

Description

(n = 5). Head capsule with frontal grooves broad for most of length, terminated mesad low convexity mesad anterior supraorbital seta; dorsal impression of neck slightly concave; ocular lobe obtusely protruded from gena, eyes small and moderately convex, ocular ratio = 1.41-1.49, ocular lobe ratio = 0.79-0.84; labral anterior margin shallowly emarginate to 1/8 labral length; antennae filiform; antennomeres 2-3 with sparse pelage of short setae; mentum tooth with sides acute, apex tightly rounded. Pronotum moderately transverse, MPW/PL = 1.18-1.25, base narrowly constricted, MPW/BPW = 1.57-1.68, lateral margins subparallel for 0.1 × pronotal length anterad right hind angles; median base distinctly depressed relative to convex disc, ~19 isolated punctures each side, half of them lining juncture between base and disc; basal margin slightly convex between laterobasal depressions; median longitudinal impression very shallow, middle of disc flat; anterior transverse impression broad, shallow, obsolete medially, crossed by indistinct wrinkles, incised only mesad front angles; anterior callosity slightly convex, crossed by indistinct longitudinal wrinkles; front angles slightly projected, tightly rounded; pronotal apical width greater than basal width, APW/BPW = 1.05-1.09; lateral marginal depression very narrow, slightly wider at front angle, thickly upraised outside laterobasal depression; laterobasal depression narrow, surface irregular, continuous with lateral depression. Proepisternum with 5 minute punctures along hind marginal groove; prosternal process with narrow lateral depression, lateral margins broadly upraised. Elytra convex, disc domed, sides distinctly sloped; basal groove evenly curved to tightly rounded humerus defined by juncture of basal groove and broader lateral marginal depression, MEW/HuW = 2.21-2.34; parascutellar seta present; parascutellar striole with 4 punctures, striole shallow or interrupted between punctures; sutural interval more convex than lateral intervals, sutural juncture upraised; sutural and 2nd striae of similar depth and punctation on disc, sutural stria continuous to base, and finely incised, deep, and smooth apically, whereas 2nd stria is absent from base, shallow and irregularly interrupted apically; discal striae 2-3 shallow, punctate, striae 4-5 very shallow to obsolete, striae 6-7 only shallow isolated punctures, or absent; elytral apex between 2nd and 8th striae uniformly convex; 2 dorsal elytral setae at 0.27 –0.29× and 0.49 –0.51× elytral length, setal impressions small, shallow, spanning ½ width of interval 3; lateral elytral setae arranged in anterior series of 6 setae and a posterior series of 5(6) setae; elytral marginal depression broader at humerus, edge little upturned there, gradually narrowed to bead at subapical sinuation; subapical sinuation shallow, more abruptly incurved anteriorly. Mesepisternum with ~10 punctures in 2-3 rows; metepisternal width to length ratio = 0.68; metepisternum/metepimeron suture distinct. Abdomen with irregular lateral wrinkles on ventrites 1-5, and lateral depressions on ventrites 3-6; suture between ventrites 2 and 3 complete; apical male ventrite with 2 marginal setae and 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 1.2 × medial tarsomere length, apical and subapical setae present; metatarsal dorsolateral sulci broad, shallow, median area subcarinate. Microsculpture of vertex a transverse mesh, sculpticell breadth 2 –3× length; pronotal disc with shallow transverse mesh to transverse lines, glossy in part, median base with shallow transverse mesh between glossy portions; elytral disc with distinct, regular transverse mesh, sculpticell breadth 2 –3× length, apex with less-developed mesh of same dimensions; metasternum with shallow transverse mesh; laterobasal abdominal ventrites with swirling isodiametric and transverse microsculpture. Coloration of vertex rufous; antennomeres 1-3 flavous, 4-11 rufoflavous; pronotal disc rufoflavous, base slightly darker, rufobrunneous; proepipleuron flavous, proepisternum dorsally flavous, ventrally rufoflavous; elytral disc rufobrunneous, sutural interval rufoflavous basally, flavous apically, lateral depression and apex of 8th interval flavous; elytral epipleuron flavous, metepisternum rufoflavous; abdomen with all ventrites medially rufoflavous, marginally flavous, apical half of apical ventrite flavous; metafemur flavous; metatibia flavous with rufoflavous cast.

Male genitalia (n = 9). Aedeagal median lobe slender, elongate, distance from parameral articulation to tip 5.6 –6.0× maximum depth of shaft (Fig. 153 D–E, G, I–J), apex nar rowly extended 3.0 –3.5× depth beyond ostial opening (Fig. 153E, J); median lobe nearly symmetrical in ventral view (Fig. 153F, H), with apex curved leftward to pointed tip in this view; internal sac with well-developed microtrichial field on right-ventral face near base (homologous with dorsal patch?), sac surface otherwise covered with fine microspicules (Fig. 153J); flagellar plate of moderate size, length 0.40 × parameral articulation-tip distance.

Female reproductive tract (n = 1). Bursa copulatrix parallel sided, elongate, with slight apical expansion, length 1.06 mm, breadth 0.29 mm (Fig. 154B); bursal walls translucent, thinly wrinkled; gonocoxite 1 with 3-4 apical fringe setae, a small seta near medioapical angle and another ~16 small setae on medial surface (Fig. 155B); gonocoxite 2 falcate with subacuminate apex, lateral margin straight near ensiform setae, terminus of basal extension slightly curved, 2 elongate lateral ensiform setae, apical nematiform setae on medioventral surface at 0.69 × gonocoxite length.

Holotype.

Male (BPBM) labeled: Kipahulu Valley / Maui Camp 2 / 1250 m, 13-17.VIII.67 // N. Wilson / Collector / BISHOP // HOLOTYPE / Mecyclothorax / nanunctus / Liebherr / det. J.K. Liebherr 2015 (black-margined red label).

Paratypes.

84 specimens (see Appendix).

Etymology.

During the initial sorting of specimens for this revision, this species was given the working name "little- unctus ." That name is validated here using the prefixed Latin participle nanunctus , or “small-anointed” ( Brown 1956).

Distribution and habitat.

Mecyclothorax nanunctus exhibits a bipartite Waikamoi plus eastern Hanawī-Kīpahulu Valley distribution (Fig. 157), with collecting localities ranging 975-1850 m elevation. Nearly all specimens are associated with ‘ōhi‘a, though one specimen was obtaining scraping koa bark. Specimens of this species have also been found in association with Astelia (painiu), and Cibotium ( hāpu‘u), in sifted litter, and by beating ferns and other vegetation at night.