Mecodema dux Britton 1949
Creators: name: Seldon, David S.
name: Buckley, Thomas R.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Carabidae
Mecodema
Mecodema dux

description: Mecodema dux Britton, 1949.
Figure 26.
Diagnosis: Distinguished from other North Island Mecodema species by: 1, the overall pronotal shape being ovate; 2, numerous punctures between pronotal foveae; 3, elytral striae 1–4 with obsolescent punctures, striae 5–8 with punctures more impressed; 4, the distinctive shape of the apical portion of the penis lobe (Fig. 26 PL).
Description: Length 19–24 mm, pronotal width 5–6 mm, elytral width 6–7.1 mm. Colour of entire body dark reddish-brown to matte black, coxae and legs reddish-brown.
Head: Narrow and convex (Fig. 14D). Vertex with short, deep wrinkles and punctures; vertexal groove narrow, defined by punctures that extend onto posterior frons area (Fig. 26); supraorbital puncture large bearing 2 setae; 5–6 moderately defined supraorbital grooves extend onto lateral area of frons; frons medially convex with a large and shallow depression anteriorly each side of midline; frontoclypeal suture (Fig. 9) narrow, well-defined the entire length, tentorial pits indistinct; anterior area of clypeus with deep grooves laterally and medially, 1 large setose puncture each side bearing 2–3 setae. Labrum lobate, anterior edge outwardly curved, very slightly emarginated medially with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded (Fig. 12F), median process broad and short, moderately angled upward (30°), strongly indentate (Fig. 12A); mentum setae absent. Submentum sclerite constriction narrow with 6 evenly-spaced setae along constriction. Stipes with 2 basal setae. Gula pits small, suture poorly defined, gula slightly convex with very fine transverse lines. Gena with rugose transverse wrinkles across entire area.
Prothorax: Prothoracic carina narrow the entire length, moderately crenulated with 7–10 setae each side (Fig. 26), extended beyond anterior angle; posterior lateral sinuation indistinctly carinate, angled inward; pronotum narrow and deflected laterally giving pronotum an almost ovate shape; midline (Fig. 11) indistinct, anterior medial triangular impression and posterior medial diamond-shaped impression present, transverse rugose wrinkles across entire disc, numerous punctures between foveae; pronotal foveae narrow and shallow; anterior edge inwardly curved, posterior edge inwardly curved medially (Fig. 26). Prosternum flat with fine transverse lines and central depression; proepisternum with numerous punctures. Procoxal setae absent; protibia distally expanded and shovellike (Fig. 10B).
Elytra: Narrow and deflected; humeral angle anteriorly convergent (Fig. 6A); basal margin curved and bevelled to base, interval 1 extended to margin, a few punctures along base; lateral carina narrow, broadened in posterior ⅓, extended to humeral angle; humerus with 2–3 setose proximate punctures anterad; suture impressed but no more so than striae; striae with small, regularly spaced, asetose punctures that increase in size laterally; striae 1–4 with obsolescent punctures, striae 5–8 with punctures impressed (some punctures star-shape); intervals 1–4 weakly convex, intervals 5–8 moderately convex, interval 9 strongly convex; intervals with fine wrinkles; 7 th strial setal pattern with 2 setose punctures in anterior ½, 5–6 setose punctures in posterior ½ (Fig. 26), setose punctures small; some specimens with setose puncture at the junction of the basal margin and interval 2.
Ventral surface: Mesepisternum with short grooves and punctures; metepisternum grooved; setose punctures present on mesocoxa (1) and metacoxa (2). All abdominal ventrites lineate, ventrites 1 and 2 (Fig. 2) may have a few scattered punctures; ventrites 3–5 with 1 setose puncture present each side of midline; ventrite 6 setae present: ♂ with a single seta each side, apical edge a rounded curve, ♀ with 2–3 pairs (may have 1–2 more pairs) of setae each side, apical edge with a rounded, narrow point; lateral foveae absent. Anterior metaventrite process a short triangle with a well-defined and broad carina the entire length.
Male genitalia: Apical portion of penis lobe asymmetrically hooked with a moderate deflection to right of vertical axis (VV) (Fig. 15B); ventral process formed by short, sharp angle to form a rounded point that is pushed forward of vertical centre (Fig. 3), apex symmetrically curved upward to form dorsal process that is short, very rounded but flattened (half discus-shaped) with a brief curve back to the shaft, posterad the vertical axis (Fig. 26 PL); penis lobe shaft narrow at apex gradually broadened to base, shaft of penis lobe straight (VV); overall length of penis lobe moderately curved ventrally (LV) (Fig. 16B). Structures of the endophallus (Fig. 4): lateral form of the apex of the central spicule pointed; dorsal form of the apex of the central spicule long and narrow; setal (scales) coverage of the apical plate moderate (26–75%); size of left setose flange small; size of right setose flange large. Left paramere basal lobe rectangular with very low dorsal hump forming a definite (60°) slope to arm; arm very short and narrow, terminal lobe not distinct from arm; very sparse, medium length setae form an apical tuft (Fig. 26 LP); ventral edge setal distribution from apical tuft, a short gap, then a medium to long-lengthed comb of setae to basal lobe-arm junction (Fig. 26 LP); ventral edge straight. Right paramere a long and narrow triangle with a double row of long setae extending along apical ¾ of ventral edge (Fig. 26 RP); apical ½ of arm inwardly curved toward penis lobe.
Female genitalia: Basal gonocoxite 1 (Fig. 5) short and broad especially apically, ventral surface with a few wrinkles, internal dorso-lateral carina with a single short seta at terminal end and inner edge of carina at base of gonocoxite 2. Gonocoxite 2 a rounded triangle, with apical portion slightly curved outward. Ramus long and narrow, broadened posterad.
Comments: Mecodema dux can be found throughout the Ruahine Ranges, there can be some morphological differences, and slight variation in the apical portion of the aedeagus among populations. These variations are more pronounced between populations on either side of the ranges, i.e. eastern and western populations.
Distribution: New Zealand, North Island, Ruahine Ranges, Hawke’s Bay, Rangitikei, Taupo.
Holotype: NZAC male labelled [card mounted, genitalia exposed (on card)]. Type [round label, outer red circle] / Oio, N.Z., 20.I.36 F. Gardener [hw] / HOLOTYPE Mecodema dux sp.n E.B.Britton. det. 1946 / E.S. Gourlay Acc. 1970 Ent. Div. / NZAC 04011194.
Material examined: 1♀, NEW ZEALAND RI Ruahine SFP, Rangitane Rd end, Kawhakau Base, 25.II–1.III.1995, Larivière. Larochelle / 700m moist, drained Nothofagus-horopito forest, rich-litter, big logs, pittraps (NZAC); 1, NEW ZEALAND, HB, eastern Ruahine Range, Swamp Loop, 11 Dec 2012 – 8 Jan 2013, D.S. Seldon & D. Brown DSS081 / pitfall traps in kahikatea-beech canopy, S39°47’38.2, E176°11’48.8, 627m (NZAC); 1, NEW ZEALAND, HB, eastern Ruahine Range, Swamp Loop, 11 Dec 2012, D.S. Seldon & D. Brown DSS082 / underlogs in kahikatea-beech canopy, S39°47’37.0, E176°11’45.0 (NZAC).
description: Published as part of Seldon, David S. & Buckley, Thomas R., 2019, The genus Mecodema Blanchard 1853 (Coleoptera: Carabidae: Broscini) from the North Island, New Zealand, pp. 1-148 in Zootaxa 4598 (1) on pages 44-46, DOI: 10.11646/zootaxa.4598.1.1, http://zenodo.org/record/2668063