Mecyclothorax obscuricornis 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 : 40-42

Taxon classification Animalia Coleoptera Carabidae

(012) Mecyclothorax obscuricornis Sharp Figs 18F, 22 E–F, 23B, 24A, 25

Mecyclothorax obscuricornis Sharp 1903: 245; Britton 1948b: 160.

Diagnosis.

The combination of standardized body length 3.4-3.6 mm, distinctly punctate discal elytral striae (Fig. 24A), convex lateral elytral margins, and narrowly paler pronotal and elytral margins serves to diagnose this species from others in the group. This species shares with Mecyclothorax obscuricolor well-developed isodiametric and transverse-mesh microsculpture on the vertex, however the pronotal disc has more transverse sculpticells–breadth 3 × length to unconnected transverse lines–and the elytral disc has only a shallow transverse mesh, sculpticell breadth 2 × length, with the surface glossy. In common with Mecyclothorax montanus , the parascutellar seta is lacking. Setal formula 2 1(2) 2 1[sae]; the species is scored for rare occurrence of both lateral and basal pronotal setae based on one individual with unilateral presence of the basal seta.

Identification

(n = 3). The eyes are little convex, ocular ratio = 1.37-1.40, and small, ocular lobe ratio = 0.74-0.79. The pronotum is moderately constricted basally, MPW/BPW = 1.43-1.46, with the lateral margins subparallel for only a short distance anterad the obtuse hind angles. The pronotal median base is moderately depressed and rugose due to the presence of large punctures and longitudinal wrinkles. The elytra are subquadrate with tightly rounded to subangulate humeral angles; MEW/HuW = 1.82-1.89.

Male genitalia (n = 2). Aedeagal median lobe (Fig. 22E) more gracile than that of Mecyclothorax obscuricolor (Fig. 22C), distance from parameral articulation to tip 4 × medial breadth, apex narrow, parallel sided, extended 2.7 × its breadth beyond ostial opening, the tip rounded; median lobe nearly straight in ventral view, right margin slightly concave before rounded tip (Fig. 22F); internal sac covered with evident microspicules, flagellar plate elongate, visible just inside dorsal margin in lateral view (Fig. 22E).

Female reproductive tract (n = 1). Bursa copulatrix columnar with rounded apex, length 0.83 mm, breadth 0.34 mm, base as broad as vagina (Fig. 23D); bursal walls translucent, thinly wrinkled; gonocoxite 1 with 2-3 apical fringe setae, 7-8 small setae on medial surface (Fig. 18F); gonocoxite 2 subfalcate, apex subacuminate, base extended laterally, 2 lateral ensiform setae, the apical seta broader and longer, apical nematiform setae on medial surface at 0.68 × gonocoxite length.

Lectotype.

Male (BMNH) hereby designated, labeled: Mecyclothorax obscuricornis Type D.S. Haleakala Perkins 120 (on mounting platen) // Type // Hawaiian Is. Perkins 1904-336 // LECTOTYPE Mecyclothorax obscuricornis Sharp J.K. Liebherr 1998 (black-margined red label).

Distribution and habitat.

Just as with Mecyclothorax obscuricolor above, Mecyclothorax obscuricornis was collected repeatedly by Perkins (Nos. 112, 113, 120, 251, 371, 372, 59 8, 600, 608) with his notes ( Perkins 1894, 1896a, 1896b) placing those collecting activities in the vicinities of Olinda and Ukulele Camp (Fig. 25). Also, as with Mecyclothorax obscuricolor , this species has not been seen in nature Perkins collected it. In 1894 he collected both species on 31-iii, 1- iv, and 6-iv, supporting their occupation of similar or at least adjacent habitats during the late 19th Century.