Mecyclothorax laetus (Blackburn)

Liebherr, James K., 2015, The Mecyclothorax beetles (Coleoptera, Carabidae, Moriomorphini) of Haleakala-, Maui: Keystone of a hyperdiverse Hawaiian radiation, ZooKeys 544, pp. 1-407 : 139-140

Taxon classification Animalia Coleoptera Carabidae

(054) Mecyclothorax laetus (Blackburn) Figs 62H, 70 J–M, 73A, 74A, 75

Cyclothorax laetus Blackburn 1881: 228; Blackburn and Sharp 1885: 216.

Thriscothorax laetus , Sharp 1903: 262.

Mecyclothorax laetus Sharp 1903: 247; Britton 1948b: 149 (synonymy, subsequent homonymy); Liebherr 2005b: 111.

Thriscothorax subconstrictus , Swezey 1954: 53, 60 (misidentification, Cibotium and rotten wood associate).

Diagnosis.

The rufobrunneous dorsal body color, narrow, cordate pronotum, and well-developed dorsal microsculpture–isodiametric on the elytra–will allow individuals of this species to be identified in the field using a hand lens (Fig. 73A). More microscopic characters amply diagnosis this species, including: 1, elytral parascutellar seta absent; 2, dorsal elytral setae absent, though a single seta may be present in rare instances; 3, vertex with shallow transverse mesh, sculpticell breadth 2 × length, and pronotal disc with transverse mesh, sculpticell breadth 2 –3× length. Setal conformation is highly variable among individuals of this species, with the basal pronotal setae present or absent, and either both apical and subapical elytral setae, or just the subapical seta present. Setal formula 2 1-2 0(1) 1-2[sae]. Standardized body length 3.9-4.6 mm.

Identification

(n = 5). The eyes are slightly to moderately convex, ocular ratio = 1.41-1.46, covering more than ¾ of the little protruded ocular lobe; ocular lobe ratio = 0.77-0.82. The antennae are submoniliform, with antennomeres 5-11 expanded apically. The pronotal lateral margin is distinctly concave anterad the right to acute hind angle, the basal sinuation extended for 1/7 the length of the pronotum. The pronotum is narrow to slightly transverse, MPW/PL = 1.13-1.23, with a somewhat variable basal constriction; MPW/BPW = 1.39-1.51. The narrow subquadrate elytra are flat medially, with discal striae 1-5 shallow and minutely punctate, stria 6 obsolete but traceable, and stria 7 absent. All intervals save the slightly convex sutural interval are only slightly convex to flat. When a single dorsal elytral seta is present, it is in the basal position; 0.24 × elytral length.

Male genitalia (n = 3). Aedeagal median lobe moderately robust, distance between parameral articulation and tip 3.4 × depth at midlength (Fig. 70J, L); apex sinuously extended beyond ostial opening, apex dorsoventrally expanded, either more dorsally than ventrally (Fig. 70J), or broadly both ventrally and dorsally (Fig. 70 L–M); median lobe straight in ventral view, but thin elongate apex offset toward right side of shaft, with right margin concave basad apex, and left margin distinctly incurved to meet apex, tip appearing tightly rounded from ventral aspect (Fig. 70K); internal sac broad, with broad, diffuse ventral ostial microtrichial field, otherwise covered only with fine microspicules (Fig. 70M); flagellar plate moderately large, length 0.49 × parameral articulation-tip distance. That the variably expanded apex represents infraspecific variation is supported by both narrower and broader apices (Fig. 70J, L) being found in males from Kīpahulu Valley, West Camp, 1900-1960 m elevation.

Female reproductive tract (n = 1). Bursa copulatrix columnar, apical lobe set off by constriction, reminiscent of a ginger jar with small lid; overall length 0.83 mm, apical lobe 0.25 mm long × 0.45 mm broad, shaft breadth 0.44 mm, and basal constriction 0.26 mm broad at vagina (Fig. 62H); bursal walls translucent, thinly wrinkled basally, apical lobe more wrinkled and less stained; gonocoxite 1 with 5 apical fringe setae, 6 smaller setae-1 at medioapical angle-along medial surface (Fig. 74A); gonocoxite 2 falcate with pointed apex, base broadly extended laterally, 2 short lateral ensiform setae, apical nematiform setae on medial surface at 0.77 × gonocoxite length.

Lectotypes.

For Cyclothorax laetus Blackburn, male designated by Liebherr (2005b: 113). For Mecyclothorax laetus Sharp, female designated by Liebherr (2005b: 114). Type locality for the former is Haleakala, Maui, ~4000 ft.; i.e. the Waikamoi area; type locality for the latter is Haleakala, Maui, 5000 ft. (R.C.L.P. lot 661; Anonymous N D), i.e. near Ukulele Camp.

Distribution and habitat.

Mecyclothorax laetus exhibits a very broad geographic distribution (Fig. 75), though the species is extensively absent from the Ke‘anae Valley and Hanawī face of Haleakalā. This absence is made the more peculiar by the very broad ecological preference suggested for this species by the disparate arrays of collecting situations. Consistent with occupation of the forests west of Waikamoi Gulch, this species has been found on mossy ‘ōhi‘a trunks, on koa trunks, and associated with Cibotium ( hāpu‘u) ferns. But it has also been collected by sifting soil around Deschampsia (hairgrass) clumps in open shrubland. More exotically, it has been collected in large numbers under the loose bark of downed alien Pinus ponderosa in a disturbed grassland on the northwest slope. And in the alien afforested areas of Polipoli Springs it has been found by grubbing in deep pine needle litter. The presence of free moisture is a constant in all of these situations, though the degree of solar insolation varies dramatically.