Mecyclothorax pusillus 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 : 149-150

Taxon classification Animalia Coleoptera Carabidae

(060) Mecyclothorax pusillus Sharp Figs 62L, 74E, 76 G–H, 78C, 80

Mecyclothorax pusillus Sharp 1903: 243; Britton 1948b: 147.

Diagnosis.

Of the four Mecyclothorax ovipennis group species from Haleakalā with setal formula 2 2 2 2- Mecyclothorax nubicola (Fig. 78A), Mecyclothorax krushelnyckyi (Fig. 78B), Mecyclothorax rusticus (Fig. 78D), and this species (Fig. 78C)- Mecyclothorax pusillus can be diagnosed by: 1, pronotal base moderately broad, MPW/BPW = 1.39-1.48; 2, pronotal hind angles projected, obtuse, the lateral margin subparallel for twice the distance of the basal articulatory socket; 3, elytra narrow relative to head, MEW/MHW = 1.85-1.93, with sides subparallel, MEW/HUW = 1.84-1.90, the humerus tightly rounded; 4, frons and vertex with evident shallow transverse-mesh microsculpture, sculpticell breadth 2 –3× length. Standardized body length 3.3-3.9 mm.

Identification

(n = 5). The head is broad with large eyes that cover much of the ocular lobe, ocular lobe ratio = 0.84-0.88, though the broad frons results in an ocular ratio lower than might be expected based on the eye size; ocular ratio = 1.45-1.48. Antennomeres 5-11 are stout, relatively short, of moniliform conformation similar to observed in Mecyclothorax nubicola . The pronotum is slightly transverse, MPW/PL = 1.19-1.29, with the base moderately constricted; MPW/BPW = 1.43-1.51. The pronotal median base is glossy due to the lack of microsculpture, but irregularly punctate with ~20 punctures each side, the punctures more elongate at juncture with disc. Elytral intervals 2-4 are nearly flat on the disc, though interval 2 is convex to the elytral apex, the sutural and 2nd striae of subequal depth. The discal striae 2-4 are discontinuous, with their punctures isolated for portions of the strial length. The pronotal and elytral microsculpture are extremely similar to that observed in Mecyclothorax rusticus : 1, pronotal disc with obsolete transverse mesh, glossy medially, with sculpticell breadth 2 –3× length laterally; 2, elytral disc with shallow isodiametric and transverse sculpticells in transverse rows, the elytral apex with an isodiametric mesh.

Male genitalia (n = 1). Aedeagal median lobe slender, distance between parameral articulation and tip 5.5 × depth at midlength (Fig. 76G), lobe angled basally with median shaft straight; apex distinctly downturned, tip rounded; median lobe distinctly curved rightward toward apex in ventral view (Fig. 76H), right and left margins slightly convergent to blunt tip in this view; internal sac with fine spicules only, flagellar plate (visible in ventral view, Fig. 76H) short, length 0.34 × parameral articulation-tip distance.

Female reproductive tract (n = 1). Bursa copulatrix columnar with rounded apex, length 0.46 mm, breadth 0.17 mm (Fig. 62L); bursal walls translucent with thin wrinkles, apex thinner, more diaphanous; gonocoxite 1 with 3 apical fringe setae, the middle seta larger, and 3-4 smaller setae along medial surface (Fig. 74E); gonocoxite 2 falcate with tightly rounded apex, base broadly extended laterally, 2 lateral ensiform setae with apical seta broader, apical nematiform setae on medial surface at 0.69 × gonocoxite length.

Lectotype.

Male (BMNH) hereby designated, labeled: Thriscothorax pusillus Type D.S. Haleakala Perkins 254 // Type // Hawaiian Is. Perkins 1904-336. //LECTOTYPE Thriscothorax pusillus Sharp J.K. Liebherr 1998 (black-margined red label).

Distribution and habitat.

Mecyclothorax pusillus is the second of Perkin’s 19th Century high-elevation Mecyclothorax triplet, with all of his records from his collecting activities made on his trips to the summit; 1830-3050 m elevation (Fig. 80). A single recent record (Kalahaku Overlook, 2870 m elevation, P.D. Krushelnycky, BPBM) places a lower-elevation population of this species in sympatry with Argentine Ant ( Liebherr and Krushelnycky 2007).