Mecyclothorax apicalis (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 : 127-128

Taxon classification Animalia Coleoptera Carabidae

(049) Mecyclothorax apicalis (Sharp) Figs 61 F–H, 62C, 63C, 65C, 67

Thriscothorax apicalis Sharp 1903: 264; Britton 1948b: 150.

Diagnosis.

This species and Mecyclothorax parapicalis share: 1, evident microsculpture, isodiametric to transverse, on the vertex and pronotal disc; 2, divergent pronotal lateral margins anterad obtuse, glabrous hind angles; 3, shallow, impunctate discal elytral intervals that are of similar color to lateral elytral intervals 7-9. The pronotum is more basally constricted in individuals of this species-MPW/BPW = 1.46-1.54-and more transverse-MPW/PL = 1.26-1.33-than in beetles comprising Mecyclothorax parapicalis (Fig. 65 C–D). The elytra are also narrower basally, with the lateral margins little extended laterally behind the tightly rounded humeri (Fig. 65C). The male aedeagal median lobe is distinctively different from that of Mecyclothorax parapicalis , with the apex sinuously recurved with an expanded, spoonlike tip (Figs 61F, G). Individuals of this species vary in the degree of punctation in the discal elytral striae. The striae vary from smooth, impunctate, to more irregular due to the presence of elongate punctulae (Fig. 65C). This variation is taken into account in the dichotomous key above. Setal formula 2 1 2 0. Standardized body length 4.0-4.2 mm.

Identification

(n = 5). Characters of the pronotum can assist identification, with the median base depressed relative to the disc, the surface strigose laterally and sparsely punctate medially. The anterior transverse impression is shallow, broad, with sparse longitudinal wrinkles behind. The laterobasal depression is slightly convex medially, and depressed laterally and basally along the beaded pronotal margin. On the elytra, the narrower elytral base is associated with a very narrow marginal depression at the humeri, with the narrow marginal depression concolorous with the elytral intervals. Overall, the body coloration is dark: 1, vertex rufobrunneous with piceous cast; 2, pronotal and elytral disc rufopiceous; 3, elytral apex narrowly flavous along margins (Fig. 65C). The frons and vertex bear well-developed isodiametric sculpticells in transverse rows. The pronotal disc is covered with isodiametric to slightly transverse sculpticells in transverse rows, the isodiametric microsculpture on the median base more upraised, again arranged in transverse rows.

Male genitalia (n = 4). Aedeagal median lobe slender, distance between parameral articulation and tip 5 × depth at midlength (Fig. 61F); apex sinuously extended beyond apex of ostial opening, dorsoventrally expanded near bluntly rounded tip; median lobe straight overall in ventral view, the apex offset to right relative to the shaft, tip blunt (Fig. 61H); internal sac with ventral ostial microtrichial patch, flagellar plate very small, length 0.24 × parameral articulation-tip distance (Fig. 61G).

Female reproductive tract (n = 1). Bursa copulatrix columnar, elongate, length 0.91 mm, breadth 0.39 mm (Fig. 62C); bursal walls moderately thick, wrinkled; gonocoxite 1 with 1-2 apical fringe setae, and only 2-4 very small setae on medial half of gonocoxite (Fig. 63C); gonocoxite 2 broadly triangular with laterally curved apex, base with broad lateral extension, 2 lateral ensiform setae with apical seta broader and longer (a minute third, basal ensiform seta present unilaterally), apical nematiform setae on medial surface at 0.68 × gonocoxite length.

Lectotype.

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

Distribution and habitat.

Mecyclothorax apicalis is a species of open Deschampsia nubigena (hairgrass) grasslands, both along the upper northwest slope and in Haleakalā Crater (Fig. 67). Beetles have been found in the moist soil of bunchgrass tufts, and by pitfall trapping. Although the species has been collected recently across its range, the Argentine Ant, Linepitheme humile (Mayr), represents a threat to persistence of its populations when the two are sympatric, as they are on the northwest slope. Ant presence has been shown to have a statistically significant negative effect on beetle abundance in that situation ( Liebherr and Krushelnycky 2007).