Mecyclothorax anthracinus, Liebherr, James K., 2015

Liebherr, James K., 2015, The Mecyclothorax beetles (Coleoptera, Carabidae, Moriomorphini) of Haleakala-, Maui: Keystone of a hyperdiverse Hawaiian radiation, ZooKeys 544, pp. 1-407 : 81-84

Taxon classification Animalia Coleoptera Carabidae

(030) Mecyclothorax anthracinus sp. n. Figs 44E, 45 F–G, 46B, 47B, 48

Diagnosis.

The small, dark-bodied beetles that comprise this species look ever so like small bits of anthracite coal, their dorsal body surface a reflective black (Fig. 44E). Also, this is the only species in the group that is characterized by absence of the parascutellar seta. The pronotum is narrow and basally constricted, MPW/PL = 1.18-1.24, MPW/BPW = 1.42-1.50, the disc covered with well-developed transverse wrinkles. The elytral intervals are convex and striation irregular, with striae 5 and 6 fused near the basal groove, and the dorsal setal impressions foveate and of diameter equal to the width of interval 3, these impressions associated with longitudinal irregularities of striae 2 and 3. The femora are flavous apically and covered with a piceous cast over their basal third; tibiae piceous. Setal formula 2 2 2 2. Standardized body length 3.6-4.0.

Description

(n = 5). Head capsule with frontal grooves deep near clypeus, straight with external carina to anterior supraorbital seta; dorsal surface of neck convex, eyes moderately convex, ocular ratio = 1.42-1.50, ocular lobe ratio 0.77-0.85; labral anterior margin broadly, shallowly emarginate, antennae filiform, antennomere 3 with sparse pelage of short setae; mentum tooth with orthogonal sides, apex pointed. Pronotum with lateral margin subparallel to convergent anterad right to acute hind angle; median base depressed relative to disc, covered with rugose wrinkles; basal margin nearly straight, slightly convex medially; median longitudinal impression shallow, finely incised, crossed by wrinkles; anterior transverse impression broad, evident, bordered anteriorly by slightly convex anterior callosity that is crossed by fine wrinkles; front angles slightly projected, rounded; anterior width subequal to broader than basal width, APW/BPW = 1.00-1.06; lateral marginal depression moderately narrow, edge upturned to beaded; laterobasal depression broad, depressed with wrinkled surface. Proepisternum with 6 minute punctures along hind marginal groove; prosternal process medially depressed, without marginal bead. Elytra subellipsoid, disc flat, sides moderately sloped; basal groove slightly recurved to tightly rounded humeral angle; humeri narrow, MEW/HuW = 2.06-2.10; parascutellar striole finely incised, continuous; sutural interval moderately convex, slightly more upraised than intervals 2-4; sutural and 2nd striae of subequal depth from base to apex; discal striae 1-8 complete and deep to apex, smooth with minute irregularities along striae suggesting punctulae; 7th and 8th intervals of similar convexity mesad subapical sinuation; 2 dorsal elytral setae at 0.32 × and 0.65 –0.73× elytral length; apical and subapical setae present; lateral elytral setae arranged in anterior series of 7 setae and posterior series of 4(5) setae; elytral marginal depression narrow, edge upturned; subapical sinuation very shallow, nearly obsolete. Mesepisternum with 8 shallow punctures in 2 rows; metepisternal width to length ratio = 0.71; metepisternum/metepimeron suture distinct, metathoracic flight wing an ovoid flap, length 2.5 × breadth, with reduced R and M veins, the flap extended 2/3 distance to hind margin of metanotum. Abdomen with indistinct lateral wrinkles on ventrites 1-3; suture between ventrites 2 and 3 complete; apical male ventrite with 2 marginal setae, apical female ventrite with 4 equally spaced marginal setae and a median trapezoid of 4, subequal short setae. Legs-metatarsomere 1/metatibial length ratio = 0.17; metatarsomere 4 length along outer lobe 1.2 × medial tarsomere length, apical and subapical setae present; metatarsal dorsolateral sulci broad, shallow. Microsculpture of vertex of granulate isodiametric sculpticells; pronotal disc covered with distinct transverse mesh, median base with granulate isodiametric sculpticells; elytral disc covered with well-developed transverse mesh, apex with well-developed isodiametric mesh in transverse rows; metasternum with upraised transverse mesh; laterobasal abdominal ventrites with swirling isodiametric and transverse microsculpture. Coloration of vertex granulate rufopiceous; antennomere 1 flavous, antennomeres 2-3 with piceous cast, 4-11 piceous; pronotal disc granulate rufopiceous, margins narrowly paler, rufobrunneous; proepipleuron rufobrunneous with piceous upper margin, proepisternum rufobrunneous with piceous cast; elytral disc rufopiceous, sutural interval paler, dark rufous throughout, margins narrowly paler basally, concolorous with disc apically; elytral epipleuron rufobrunneous, metepisternum rufopiceous; abdomen rufopiceous across width of ventrites 1-5, apical ventrite 6 with apical 1/3 paler, rufobrunneous.

Male genitalia (n = 1). Aedeagal median lobe curved, gracile, distance from parameral articulation to tip 4 × depth at midlength (Fig. 45F); apex angularly narrowed to tightly rounded tip formed at juncture of flat apical face and ventral margin; median lobe sinuously recurved left then right in ventral view (Fig. 45G), tip tightly rounded; internal sac with apparent dorsal ostial microtrichial patch (based on uneverted specimen; Fig. 45F), sac surface covered with microspicules; flagellar plate evident just inside dorsal margin of median lobe.

Female reproductive tract (n = 1). Bursa copulatrix a narrow digitiform lobe attached to broader vagina, lobe length 0.26 mm, lobe apical breadth 0.10 mm, vagina breadth 0.25 mm (Fig. 46B); bursal walls thin, transparent; gonocoxite 1 with 3 apical fringe setae and 5-6 smaller setae on medial surface (Fig. 47B); gonocoxite 2 falcate, narrow apically with base broadly extended laterally, 2 lateral ensiform setae with apical seta broader and longer, apical nematiform setae on medial surface at 0.75 × gonocoxite length.

Holotype.

Female (BPBM) labeled: NW 6000'-6500', / Haleakala / VIII-18-37 Maui // Beating // ECZimmerman / Collector // 3 // HOLOTYPE / Mecyclothorax / anthracinus / Liebherr / det. J.K. Liebherr 2015 (black-margined red label).

Paratypes.

HI: Maui: Haleakala N.P., NW upper slope, beating 1830-1980 m el., 18-viii-1937, Zimmerman (BPBM, 2); Koolau For. Res., Hanawi N.A.R., Frisbee Meadow Camp, woods below, sift litter Dubautia /tree, 2072-2099 m el., 19-v-1993 lot 01, Liebherr/Medeiros (CUIC, 6).

Etymology.

The shiny coal black color of the dorsal surface of these beetles begs for use of the Latin adjective anthracinus .

Distribution and habitat.

Mecyclothorax anthracinus is known from two isolated, high-elevation localities near the upper limits of the windward forest. E.C. Zimmerman beat three specimens from vegetation at 1830-1980 m elevation along the NW upper slope, and six specimens were taken from leaf litter samples of Dubautia reticulata litter at "Frisbee Meadow Camp" in the headwaters of Hanawī Stream to the east (Fig. 48). Whether the unusual coal-black color and ridged dorsal body surface of Mecyclothorax anthracinus beetles serve to enhance crypsis on the dark, fissured bark of the tree Dubautia seems a question worthy of study.