Mecyclothorax cognatus 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 : 54-56

Taxon classification Animalia Coleoptera Carabidae

(018) Mecyclothorax cognatus Sharp Figs 28C, 29 E–H, 30B, 31B, 32

Mecyclothorax cognatus Sharp 1903: 255; Britton 1948b: 165.

Atelothorax optatus Sharp 1903: 269; Britton 1948b: 165 (synonymy).

Diagnosis.

Among the mid-sized species in this group-standardized body length 4.7-5.7 mm-this species exhibits the broadest body in both pronotal and elytral dimensions. The pronotum is transverse, MPW/PL = 1.26-1.33, and basally broad, MPW/BPW = 1.31-1.42. This species is broadly sympatric in the Waikamoi area with Mecyclothorax consanguineus , the species most similar in appearance and thus likely to cause confusion. Mecyclothorax cognatus can be distinguished by the broad elytra (Fig. 28C), with broad humeri, MEW/HuW = 1.83-1.94 versus MEW/HuW = 1.91-2.04 for Mecyclothorax consanguineus (Fig. 33B). The pronotum of Mecyclothorax cognatus also exhibits more broadly explanate lateral margins just before the hind angles, that area broadly extended from the deep, smooth laterobasal depressions. Mecyclothorax consanguineus conversely exhibits less explanate lateral margins at that position. If a male is available, the aedeagal tip is absolutely diagnostic even if extended only slightly from the specimen. Those of Mecyclothorax cognatus males have an angulate apex with subangulate tip (Fig. 29 E–G), whereas those of Mecyclothorax consanguineus males have an elongate apex with a mucronate tip (Fig. 34 A–I). Sharp (1903) described Atelothrus optatus based his interpretation that the lateral pronotal setae were missing in the unique type specimen. The left lateral seta is indeed absent, but the articulatory socket for the right lateral seta is evident, resulting in the species setal formula being scored here as 2 2(1) 2 2.

Identification

(n = 5). The eyes are moderately developed-ocular ratio = 1.41-1.46, ocular lobe ratio = 0.75-0.81-with the ocular lobe smoothly joined to the gena. The pronotal front angles are broadly protruded, subangulate externally, with the anteriorly broad pronotal lateral marginal depression narrowed to the position of the lateral seta, and then broadened toward the back of the pronotum. The elytral striae are present across the width of the elytra, depth of striae 6 and 7 subequal to slightly shallower than striae 1-5 and 8. The discal elytral intervals are only slightly convex, with very fine punctures in the associated striae. The metepisternum bears ~16 punctures in 2-3 rows, about twice as many punctures as seen in Mecyclothorax consanguineus . Cuticular microsculpture is essentially identical to that observed in Mecyclothorax consanguineus : 1, vertex with transverse mesh, sculpticell breadth 2 × length; 2, pronotal disc with transverse mesh, sculpticell breadth 2 –3× length; 3, pronotal base with distinct isodiametric and transverse sculpticells; 4, elytral disc with transverse mesh, sculpticell breadth 3 –4× length; and 5, elytral apex with transverse mesh, sculpticell breadth 3 × length, to transverse lines.

Male genitalia (n = 6). Aedeagal median lobe gracile with broad, trapezoidal apex, distance from parameral articulation to tip 4.1 × median breadth (Fig. 29G), apex with flat ventral and apical faces, the tip angulate; median lobe nearly straight in ventral view, the right margin concave, and left margin incurved before the apparently rounded tip (Fig. 29H); internal sac broad, parallel sided, with moderate dorsal microtrichial patch and smaller ventral microtrichical patch that is near base of sac (Fig. 29 E–F); flagellar plate well sclerotized, length 0.42 × distance from parameral articulation to tip.

Female reproductive tract (n = 1). Bursa copulatrix columnar with rounded apex, length 1.32 mm, breadth 0.46 mm, base as broad as vagina (Fig. 30B); bursal walls translucent with thick wrinkles; gonocoxite 1 with 4 apical fringe setae, 6-7 smaller setae on medial surface (Fig. 31B); gonocoxite 2 narrowly subtriangular with subacuminate apex, base narrowly extended laterally, 2 lateral ensiform setae with apical seta broader, apical nematiform setae on medioventral surface at 0.73 × gonocoxite length.

Types.

For Mecyclothorax cognatus Sharp holotype female (BMNH) labeled: Mecyclothorax cognatus Type D.S. Haleakala Perkins 111 // Type // Hawaiian Is. Perkins 1904-336. // Haleakala Maui 5000 ft. Perkins IV 1894 // Atelothorax optatus Sharp compared with type E.B.B. // HOLOTYPE Mecyclothorax cognatus Sharp J.K. Lieb herr 1998 (black-margined red label). For Atelothorax optatus Sharp holotype male (BPBM) platen mounted and labeled: Atelothorax / optatus / Type / D.S. / Haleakala / 1902 (written on obverse of mounting card) // Mecyclothorax / cognatus Sharp / Compared / with type E.B.B. // HSPA # / 1960 // HOLOTYPE / Atelothorax / optatus / Sharp / J.K. Liebherr 1998 (black-margined red label).

Distribution and habitat.

Mecyclothorax cognatus is restricted to forests in the Waikamoi region (Fig. 32) from 1200-1850 m elevation. The only recorded Perkins lot (No. 111) was collected iv– 1894 near Ukulele Camp, with modern collections centered on the Ukulele Pipeline Koa- ‘Ōhi‘a Mesic Forest at ~1500 m elevation northeast of the Ukulele Camp site. Beetles occur on and under bark of koa , in moss on trunks of ‘ōhi‘a, and on the ground in the leaf litter or under logs. Several have been collected in yellow-pan traps set on the ground.