Mecyclothorax subconstrictus (Sharp)

Liebherr, James K., 2015, The Mecyclothorax beetles (Coleoptera, Carabidae, Moriomorphini) of Haleakala-, Maui: Keystone of a hyperdiverse Hawaiian radiation, ZooKeys 544, pp. 1-407 : 145-146

Taxon classification Animalia Coleoptera Carabidae

(057) Mecyclothorax subconstrictus (Sharp) Figs 62K, 73D, 74D, 76 E–F, 79

Thriscothorax subconstrictus Sharp 1903: 259.

Mecyclothorax subconstrictus , Britton 1948b: 147.

Diagnosis.

This, the third species of the group to exhibit setal formula 2 1 1 0 for at least some individuals, can be diagnosed from the other two- Mecyclothorax cordaticollis (Fig. 73B) and Mecyclothorax cordaticollaris (Fig. 73C)-by the following combination: 1, pronotal hind angles obtuse, lateral margin divergent from angle (Fig. 73D), not parallel before angle; 2, elytra broader relative to pronotal width, MEW/MPW = 1.53-1.66, versus values of 1.47-1.52 observed in specimens of the other two species; 3, elytral disc with mixture of isodiametric and transverse sculpticells, sculpticell breadth 2 × length, versus more transverse meshes in the other two species. Setal formula 2 1 1(2) 0; individuals have a posterior dorsal elytral seta present unilaterally in rare instances. Standardized body length 3.7-4.3 mm.

Identification

(n = 5). The eyes are slightly larger and more convex than observed in Mecyclothorax cordaticollis and Mecyclothorax cordaticollaris -ocular ratio = 1.46-1.52, ocular lobe ratio = 0.81-0.88-though the ratios for the three species overlap. In aggregate the pronotal apex is broader relative to the base; APW/BPW = 1.03-1.09. The impressions of the anterior dorsal elytral setae span 2/3 of interval 3, whereas the impression of a posterior seta, if present, is small, spanning half or less of interval 3. The body coloration overall is also darker in specimens of this species versus those of the former two; 1, vertex and pronotal disc rufobrunneous with piceous cast; 2, pronotal lateral margins dark and concolorous with disc, though base and apex paler, rufoflavous.

Male genitalia (n = 1). Aedeagal median lobe robust, distance between parameral articulation and tip 2.9 × depth at midlength (Fig. 76E); apex extended twice its depth beyond ostial opening, tip tightly rounded but with minute denticle along dorsal margin; median lobe slightly curved rightward in ventral view, left and right sides subparallel as they moderately converge to blunt-appearing tip (Fig. 76F); internal sac covered with dark microspicules, flagellar plate elongate, length 0.50 × parameral articulation-tip distance.

Female reproductive tract (n = 1). Bursa copulatrix broadly ellipsoid with constricted base, length 0.88 mm, breadth 0.44 mm, basal constriction at vagina 0.31 mm broad (Fig. 62K); bursal walls translucent with thin wrinkles; gonocoxite 1 with 2 short apical fringe setae and 4-6 small setae along medial surface (Fig. 74D); gonocoxite 2 broadly triangular with broadly rounded apex (apex worn), 2 lateral ensiform setae with apical seta longer and broader, apical nematiform setae on medial surface at 0.72 × gonocoxite length.

Lectotype.

(BMNH) hereby designated, left specimen on mounting platen, labeled: Thriscothorax subconstrictus Type D.S. Haleakala Perkins // Type // Hawaiian Is. Perkins 1904-336. // LECTOTYPE Thriscothorax subconstrictus Sharp J.K. Liebherr 1998 (black-margined red label).

Distribution and habitat.

Mecyclothorax subconstrictus is one of four species in the Mecyclothorax ovipennis group that occupy the highest elevations at the summit of Haleakalā (Figs 79, 80). Most specimens of these species were collected 9-iv-1894 during Perkins’ ascent of Haleakalā from Ukulele Camp. In Perkins’ words: "April 9th. Started with rug, food and gun etc. for Blackburn’s cave at about 9000 feet. I got there about 10 a.m. although I went down to nearly Olinda before ascending, as I wished to go on the usual trail. Worked from 9000 ft. to the summit. Got 3 or 4 species of Cyclothorax , the large punctured species as below, [i.e. Mecyclothorax montivagus , common from 4000-10000 ft.] the small ones all new to me apparently." He returned to the summit two days later, collecting many more Mecyclothorax specimens. Besides Mecyclothorax subconstrictus , the species new to Perkins were Mecyclothorax pusillus and Mecyclothorax rusticus . These two collecting hikes occurred "a few weeks after the disappearance of the snow-cap ( Perkins 1913, cxl)." Mecyclothorax subconstrictus was collected again in May and October 1896, the latter time at Holua in Haleakalā Crater. It has not been recollected since.