Mecyclothorax bilobatus, 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 : 277-279

Taxon classification Animalia Coleoptera Carabidae

(110) Mecyclothorax bilobatus sp. n. (Figs 145D, 146D, 149A, 150, 151

Diagnosis.

Among the four species in this group with individuals exhibiting contrastedly paler elytral margins, this species (Fig. 149A) is diagnosed by the very shallow elytral striae, with only the sutural and 2nd striae impressed on the disc. The pronotal median base is less punctate than in the two bicolored species with punctate striae; Mecyclothorax bicoloris (Fig. 143C) and Mecyclothorax bicoloratus (Fig. 143D). In this species the pronotum has ~16 isolated punctures each side, and the surface of the pronotal laterobasal depression is smooth. The male aedeagal internal sac is bilobed in this species, with the basal lobe subequal in length to the apical lobe (Fig. 150 E–F). Setal formula 2 1 2 0. Standardized body length 3.9-4.7 mm.

Description

(n = 5). Head capsule with frontal grooves broad and deep at clypeus, straight and subparallel, terminated at a low carina mesad anterior supraorbital seta; dorsal impression of neck slightly concave; ocular lobe obtusely protruded from gena, eyes convex, ocular ratio = 1.54-1.60, ocular lobe ratio = 0.78-0.81; labral anterior margin angularly emarginate 1/6 of labral length; antennae filiform, antennomeres 2-3 with sparse pelage of short setae; mentum tooth with sides acute, apex tightly rounded. Pronotum slightly transverse, MPW/PL = 1.15-1.20, basally constricted, MPW/BPW = 1.53-1.64, lateral margins briefly sinuate anterad acute, projected hind angles; median base depressed relative to disc; basal margin indistinctly trisinuate, slightly convex medially; median longitudinal impression very shallow, broad, crossed by indistinct transverse wrinkles; anterior transverse impression broad, very shallow medially, incised laterally mesad front angles; anterior callosity flat, slightly upraised, smooth; front angles not projected, rounded posterad curve of front margin; pronotal apical width variably subequal to broader than pronotal basal width, APW/BPW = 0.97-1.13; lateral marginal depression moderate, edge upturned at hind angle, beaded anterad inside basal sinuation, depression not wider at front angle. Proepisternum with 5 minute punctures along hind marginal groove; prosternal process with broad median depression, lateral margins broadly beaded between coxae. Elytra subovoid, disc convex, sides distinctly sloped to margins; basal groove evenly curved to angulate humerus, MEW/HuW = 2.14-2.36; parascutellar seta present; parascutellar striole with 4 isolated punctures; sutural interval coplanar with lateral intervals basally, upraised in apical half; sutural stria deeper than 2nd stria throughout length, deeper and more punctate on disc, a series of isolated punctures near basal groove, and deep, narrow, and smooth at elytral apex; discal striae 2, or 2-3 traceable as linear series of shallow punctures, lateral striae traceable only as disturbances in the microsculpture, or melanic spots in the cuticle; striae 2, 3 and the apex of 7 shallow and traceable at elytral apex, area between striae 2 and 7 evenly convex there; 2 dorsal elytral setae at 0.26 –0.28× and 0.49 –0.57× elytral length, setal impressions small, shallow, spanning ½ width of interval 3; apical and subapical setae absent; lateral elytral setae arranged in anterior series of 7 setae and posterior series of 6 setae; elytral marginal depression narrow at humerus, margin upturned, beaded posteriorly near subapical sinuation; subapical sinuation shallow, more abruptly incurved anteriorly. Mesepisternum with 5 punctures in 1 row; metepisternal width to length ratio = 0.68; metepisternum/metepimeron suture distinct. Abdomen with irregular lateral wrinkles on ventrites 1-5, 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 = 0.18; metatarsomere 4 length along outer lobe 1.3 × medial tarsomere length, apical and subapical setae present; metatarsal dorsolateral sulci broad, shallow, median area broad. Microsculpture of vertex a shallow transverse mesh, sculpticell breadth 2 –3× length; pronotal disc with obsolete transverse mesh, sculpticell breadth 2 –4× length, median base glossy medially, indistinct isodiametric sculpticells laterally; elytral disc and apex with indistinct isodiametric sculpticells in transverse rows; metasternum with shallow transverse mesh; laterobasal abdominal ventrites with swirling isodiametric and transverse sculpticells. Coloration of vertex rufous; antennomeres 1-3 flavous, 4-11 rufoflavous; pronotal disc rufobrunneous, lateral margins, base, and anterior callosity rufoflavous; proepipleuron flavous, proepisternum rufobrunneous with rufoflavous margins; elytral disc rufopiceous, base rufobrunneous, sutural interval basally rufous, apical half rufoflavous, marginal intervals 7-9 contrastedly flavous, apex flavous apicad the posterior seta of the lateral setal series; elytral epipleuron flavous, metepisternum rufobrunneous; abdomen with ventrite 1 rufoflavous, ventrites 2-3 rufopiceous with flavous apex, ventrites 4-6 basally rufobrunneous, apical ¾ of apical ventrite 6 flavous; metafemur flavous; metatibia flavous with rufoflavous cast.

Male genitalia (n = 7). Aedeagal median lobe robust, distance from parameral articulation to tip 2.5 –2.8× depth at midlength (Fig. 150A, C–F); apex a smoothly curved extension of ventral margin, the extension of variable depth (Fig. 150A versus C–F); median lobe broad, symmetrical in ventral view, the convex dorsal margin (Fig. 150A) visible as convex apical margin in this view (Fig. 150B); internal sac with well-developed basal lobe that is subequal in length to apical lobe (Fig. 150 E–F), the lobe varying in breadth; sac with well-developed microspicules on ventral surface, a very diffuse patch of somewhat larger, lightly melanized macrospicules present near base (Fig. 150E); flagellar plate of moderate size, length 0.38 –0.40× parameral articulation-tip distance.

Female reproductive tract (n = 1). Bursa copulatrix broad basally, with parallel-sided apical lobe with rounded apex, overall length 0.76 mm, apical lobe 0.56 mm long × 0.34 mm broad, base at vagina 0.55 mm broad (Fig. 145D); bursal walls translucent, thinly wrinkled; gonocoxite 1 with 3 apical fringe setae, 7-8 smaller setae on medial surface (146D); gonocoxite 2 falcate, with tightly rounded tip, base with long thick lateral extension that curves at terminus, 2 lateral ensiform setae, apical nematiform setae on medial surface at 0.76 × gonocoxite length.

Holotype.

Male (CUIC) labeled: HI:Maui Haleakala / Hanawi N.A.R. Poouli / Cabin 6-V-1998 lot01 / 1590m el. pyrethrum fog / mossy ohia J.K. Liebherr // HOLOTYPE / Mecyclothorax / bilobatus / Liebherr / det. J.K. Liebherr 2015 (black-margined red label).

Paratypes.

103 specimens (see Appendix).

Etymology.

The adjectival species epithet bilobatus refers to the bilobed internal sac of the male aedeagus (Figs 150 E–F).

Distribution and habitat.

Mecyclothorax bilobatus is known only from upper Kuhiwa and Helele‘ike‘oha Stream drainages, and Horseshoe Bog just mauka, i.e. uphill, from the Helele‘ike‘oha State Fence Camp (Fig. 151). These sites range 1590-1830 m elevation. All specimens of this species have been collected in association with mossy ‘ōhi‘a trunks and horizontal nurse logs.