Mecyclothorax insolitus (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 : 251-253

Taxon classification Animalia Coleoptera Carabidae

(101) Mecyclothorax insolitus (Sharp) Figs 133B, 134 B–K, 135, 136A, 137A

Thriscothorax insolitus Sharp 1903: 261.

Mecyclothorax insolitus , Britton 1948b: 141.

Diagnosis.

This species (Fig. 133B) and Mecyclothorax invisitatus (Fig. 133C) comprise a cryptic sibling species pair that can be best diagnosed externally by the breadth of elytra relative to the pronotum. In this species the elytra are broader, subovoid, with MEW/MPW = 1.63-1.69, whereas in Mecyclothorax invisitatus recorded values are 1.52-1.62. The pronotal disc bears obsolete transverse-mesh and transverse-line microsculpture in this species, whereas the disc surface is glossy in Mecyclothorax invisitatus . As there are no other reliable external characters that can separate these species, their recognition lies heavily on the differing configurations of the male aedeagal median lobe. Males of this species exhibit a median lobe with the apex expanded both dorsally and ventrally, and more flattened apically (Fig. 134 F–K). The apex may be displaced dorsoventrally relative to the more basal portion of the shaft giving it a "prehensile proboscis" appearance. Conversely, the median lobe of Mecyclothorax invisitatus males is expanded only dorsally into a "crochet hook" apex, with the apical margin evenly rounded; a conformation also observed in males of Mecyclothorax reiteratus (Fig. 107). In the specimens available, the elytral apex is less broadly flavous in Mecyclothorax insolitus (Fig. 133B) compared to Mecyclothorax invisitatus (Fig. 133C), but the diagnostic value of this feature should be confirmed through examination of the male median lobe apex. Setal formula 2 1 2 0. Standardized body length 4.2-5.1 mm.

Identification

(n = 5). [Only non-diagnostic values for the various recorded ratios are presented for this species, as the qualitative attributes not in the above diagnosis are presented under Mecyclothorax invisitatus .] Eyes moderately convex, ocular lobe protruded obtusely from gena; ocular ratio = 1.52-1.56, ocular lobe ratio = 0.82-0.84. Pronotum moderately transverse, MPW/PL = 1.17-1.24, pronotal apical width variably subequal to basal width, APW/BPW = 0.92-1.07. Elytra broadly subovoid, MEW/HuW = 2.33-2.51.

Male genitalia (n = 13). Aedeagal median lobe gracile, distance from parameral articulation to tip 4.0 –4.3× depth at midlength (Fig. 134B, D, F–G, I, K); median lobe apex variable, a very short knoblike tip (Fig. 134B, D), a more hooklike tip that includes a dorsal tooth (Fig. 134G, I, K), or a dorsoventrally expanded tip intermediate to those two configurations (Fig. 134F) (in all conformations the ventral margin is expanded at the tip); median lobe curved approximately 60° rightward apically in ventral view (Fig. 134C, E, J), the terminal knob or hook defining different profiles of the tip; internal sac with dorsal ostial microtrichial patch composed of stout macrospicules on right side (Fig. 134F, H), and ventral ostial microtrichial patch on left-ventral side (Fig. 134H), the sac otherwise covered with indistinct spicules; flagellar plate elongate, length 0.50 × parameral articulation-tip distance. That the variation in tip configuration is infraspecific is attested to, in part, by sympatry of males exhibiting the knob configuration (Fig. 134D) and the dorsoventrally expanded tip (Fig. 134F) at Kula Pipeline Rd. near Waikamoi Gulch. The hooked aedeagal tip is observed in the eastern portion of the range, from Ko‘olau Gap/ Ke‘anae Valley to Kuhiwa Valley, however it varies from exhibiting a straight ventral margin (Fig. 134G, I), to an angled margin (Fig. 134K). Similarly, the knob configuration varies within the Waikamoi sites (Fig. 134B, D, H). This instability in the aedeagal median lobe apex configuration within sites is coupled with lack of any diagnosable differences in external characters, aedeagal curvature (Fig. 134C, E, J), or spiculation of the internal sac (Fig. 134F, H) for specimens assigned to this species. This combination of observations supports circumscription of Mecyclothorax insolitus as a species that exhibits variability in the configuration of the aedeagal median lobe apex.

Female reproductive tract (n = 1). Bursa copulatrix cylindrical, with skirted basal constriction, smooth middle portion, and thinly wrinkled apex, length 1.08 mm, apical width 0.51 mm, skirted basal constriction 0.26 mm broad (Fig. 136A); bursal walls translucent, base and middle portion stained more intensely, thicker; gonocoxite 1 with 3 apical fringe setae, a curved seta at medioapical angle and 5-6 smaller setae on medial surface (Fig. 137A); gonocoxite 2 subacuminate with elongate, curved basal extension, 2 lateral ensiform setae, apical nematiform setae on medioventral surface at 0.70 × gonocoxite length.

Holotype.

Female (BMNH) labeled: Thriscothorax insolitus Type D.S. Haleakala Perkins 845 // Type // Hawaiian Is. Perkins 1904-336. // HOLOTYPE Thriscothorax insolitus Sharp J.K. Liebherr 1998 (black-margined red label).

Distribution and habitat.

Mecyclothorax insolitus is distributed across windward Haleakalā from the Waikamoi area east to Kuhiwa Valley (Fig. 135). The species is known from low to moderate elevations; 880-1470 m. It has been collected in association with koa , ‘ōhi‘a, and Cibotium ( hāpu‘u), though it has been also collected in leaf litter siftate, from a steep streambank, and under boards in ‘Ōhi‘a Wet Forest along Waikamoi Flume, 1310 m elevation.