Mecyclothorax globosus Britton, 1948: 113; Perrault, 1978b: 152; 1989: 60

Liebherr, James K., 2013, The Mecyclothorax beetles (Coleoptera, Carabidae, Moriomorphini) of Tahiti, Society Islands, ZooKeys 322, pp. 1-170 : 108-109

91. Mecyclothorax globosus Britton, 1948: 113; Perrault, 1978b: 152; 1989: 60

Thriscothorax constrictus Britton, 1938: 104 (junior homonym; Britton 1948).

Identification.

Among the Mecyclothorax globosus group species with two supraorbital setae each side and only the anterior dorsal elytral setae, setal formula 2111, this species can be diagnosed from all but Mecyclothorax paraglobosus by: 1, small body size, standardized body length 3.5-4.1 mm; 2, broadly ovate and convexly domed elytra (Fig. 46B); 3, basally constricted pronotum, MPW/BPW = 1.53-1.64 (n = 5); and 4, discal elytral intervals covered with an evident transverse mesh, sculpticells isodiametric to transverse with breadth 2 × length. This species can be reliably diagnosed from Mecyclothorax paraglobosus only by the conformation of the male aedeagal median lobe. In males of this species, the lobe apex is short and broadly rounded with little to no expansion dorsoventrally from the apex of the ostial opening to the tip (Figs 47 A–C). The median lobe apex varies in dorsoventral breadth (Fig. 47B versus 47C), but it is always short relative to its breadth. The male aedeagal median lobe of Mecyclothorax paraglobosus males, in contrast, is more elongate apicad the ostial opening, with the tip slightly expanded and asymmetrically downturned (Fig. 47D). Perrault (1989) diagnosed these two species using pronotal dimensions, characterizing Mecyclothorax paraglobosus by a more transverse pronotum. At the extremes this is so, but the ratios of MPW/PL and MPW/BPW overlap substantially precluding diagnosis. In this species MPW/BPW = 1.53-1.64 (n = 5), and MPW/PL = 1.21-1.28. The frons and vertex bear shallow transverse-mesh microsculpture, the sculpticells on the neck more developed and therefore visible in reflected light. The pronotal disc is covered with an evident transverse mesh, sculpticell breadth 2 –4× length. Standardized body length 3.5-4.1 mm.

Variation. Limited setal variation occurs among individuals of this abundant, geographically widespread species. A large series of 77 individuals - Mt. Marau, 1335 m el., 15-ix-2006 lot 01 (CUIC) - includes 2 individuals with just the posterior supraor bital seta, 1 with two supraorbital setae on the right side versus one on the left, and 74 with the usual 2111setal formula. Perrault (1978b) noted that some individuals unilaterally possessed two dorsal elytral setae, however in the much larger amount of comparative material available in 1989, he stated that the species is essentially invariant ( Perrault 1989), indicating that such setal sports are exceedingly rare.

Distribution and habitat.

This species is broadly distributed on Monts Marau and Aorai, with recorded localities from 1100-1380 m elevation on the former, and 1067-1900 m elevation on the latter. Based on pyrethrin fog samples, these beetles occupy moss-covered Weinmannia growth, ferns (both low ferns such as Dicranopteris , and also Cyathea tree ferns), and the axils of Freycinetia plants, perferrably dead and rotting, the more likely to provide food sources such as dipteran larvae. During recent surveys, of the 318 specimens of Mecyclothorax collected on Mont Marau, Mecyclothorax globosus individuals accounted for 151.