Mecodema hector Britton, 1949

Seldon, David S. & Buckley, Thomas R., 2019, The genus Mecodema Blanchard 1853 (Coleoptera: Carabidae: Broscini) from the North Island, New Zealand, Zootaxa 4598 (1), pp. 1-148 : 55-57

Mecodema hector Britton, 1949 .

Figure 31 .

Diagnosis: This species differs from other North Island Mecodema species by having: 1, the vertex and vertexal groove without punctures; 2, anterior area of clypeus convex medially in front of suture, grooves anterad raised area, 1 large setose puncture each side bearing 2 distinctly separate setae; 3, the shape of the apical portion of the penis lobe ( Fig. 31 PL).

Description: Length 27.61 mm, pronotal width 7.2 mm, elytral width 8.68 mm. Colour of entire body very dark reddish-brown.

Head: Broad and flat ( Fig. 14A ). Vertex smooth; vertexal groove ( Fig. 9 ) broad and slightly impressed, defined laterally by indistinct wrinkles and a few scattered pits; large supraorbital puncture bearing 4–5 setae; 2–3 poorly defined supraorbital grooves; frons with a large and shallow depression each side of midline; frontoclypeal suture deep and narrow, tentorial pits ( Fig. 9 ) small; anterior area of clypeus medially convex anterad suture, grooves anterad raised area, 1 large setose puncture each side bearing 2 separated setae. Labrum rounded, anterior edge straight and slightly emarginated with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded ( Fig. 12F ), median process very narrow, slightly angled upward (15°), indentation notched ( Fig. 12D ); mentum setae absent. Submentum sclerite constriction broad with 3 setose punctures each side (large space medially). Stipes with 2 basal setae. Gula pits very small, suture defined, gula ( Fig. 9 ) weakly convex with very fine transverse lines. Gena with fine wrinkles forming an isodiametric pattern across entire area.

Prothorax: Prothoracic carina narrow the entire length (broadened slightly at shoulder), slightly crenulated with 6–7 setae each side, extended beyond anterior angle; posterior lateral sinuation ( Fig. 11 ) indistinctly carinate, inwardly angled ( Fig. 31 ); pronotum broad and deflected laterally, overall shape cordate; midline well-defined, anterior medial and posterior medial diamond-shaped impressions present, disc smooth; pronotal foveae deep and broad; anterior edge slightly inwardly curved, posterior edge relatively straight. Prosternum ( Fig. 2 ) with large medial depression, sparsely micropunctate increased laterally; proepisternum micropunctate. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Narrow and slightly deflected laterally; humeral angle evenly convex ( Fig. 6B ); basal margin sharply angled and gently sloped to base, interval 1 extended to scutellum; lateral carina narrow the entire length, extended to humeral angle; humerus with 2 setose punctures proximate humeral angle, 1 setose puncture posterad the humeral angle ( Fig. 31 ); suture impressed but no more so than the striae; striae 1–4 impressed as lines, asetose punctures absent, striae 5–8 with asetose punctures visible, especially towards apex; intervals 1–6 flat or weakly convex (convexity increased laterally), intervals 7 and 8 strongly convex in anterior ⅓, to moderately convex apically, interval 9 shortened and moderately convex the entire length; interval microsculpture absent; 7 th strial setal pattern ( Fig. 1 ) with 2 setose punctures in anterior ½, 2 setose punctures in posterior ½, setose punctures large.

Ventral surface: Mesepisternum with numerous grooves and pits; metepisternum ( Fig. 2 ) with wrinkles and very sparsely pitted; setose punctures present on mesocoxa (4) [anterior punctures in a line of 3] and metacoxa (2). Abdominal ventrites 1 and 2 finely lineate and sparsely pitted, ventrites 3–5 finely lineate with 2 setose punctures each side of midline; ventrite 6 setae present: ♂ with 4–6 setose punctures on each side along straight apical edge, no ♀ specimen available; ventrites 3–5 foveate laterally. Anterior metaventrite process an almost equal-sided triangle with a narrow 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 very short and steep curve forming a sharp point ( Fig. 31 PL), apex with broadly rounded (almost symmetrically) curve that forms a broad but flattened dorsal process with a recurved hook posterad the central vertical axis ( Fig. 31 PL), brief curve from hook to shaft; penis lobe shaft narrow but slightly broadened to base, very distinct curve to right, especially in apical ⅓ (VV), overall length of penis lobe slightly curved ventrally (LV) ( Fig. 16A ). 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 greatly expanded without projection; setal (scales) coverage of the apical plate extensive (26–75%); size of left setose flange small; size of right setose flange large. Left paramere basal lobe a small rectangle with moderate dorsal hump forming a steep (60°) rounded curve to very truncated arm ( Fig. 31 LP); arm and terminal lobe indistinct from each other, apical tuft of very long with numerous setae, medium length setae continue along apical ½ of ventral edge ( Fig. 31 LP); ventral edge moderately curved. Right paramere a long and narrow rectangle, gradually narrowed to form terminal end with a double row of long setae extended along apical ¾ of ventral edge ( Fig. 31 RP).

Female genitalia: no female specimen available.

Comments: Type locality mislabelled by Britton (1949) as Otago , but was corrected by Larochelle & Lariviere (2001) to Mt Hector, Wellington region.

Distribution: New Zealand, North Island, Wellington, Tararua Range, Mt Hector.

Holotype: MONZ male labelled [card mounted, genitalia exposed (on card)]. Type [round label, red outer circle] glued to card, Hector, 26.12.10 [hw] (underside of card) / Det. E.B. Britton [hw] / AI.000036.

Material examined: 1♂ Tararuas 20.12.20 [hw] / Mecodema hector Britton 1949 Det. A. Larochelle ( NZAC) .

Figures

FIGURE 1. Dorsal view of a Mecodema specimen showing taxonomic structures used in the species descriptions. H =head; P = pronotum; E = elytra; S = striae; I1 = interval 1; A = apex; 7S = 7 th strial setae; HSP = humerus setose puncture; HA = humeral angle; BM = basal margin; P = protibia.

FIGURE 2. Ventral view of a Mecodema specimen showing specific morphological structures, excluding taxonomic structures indicated in detail figures, used in the species descriptions. ƑLF = ventrite lateral foveae; ƑSP = ventrite setose punctures; MTC = metacoxa; MTƑP = metaventrite process; MSC = mesocoxa; PC = procoxa; PS = prosternum; G = gena; PES = proepisternum; MSE = mesepisternum; MTE = metepisternum; Ƒ1–Ƒ6 = ventrites 1-6 (ventrites 1-3 may be fused); M = midline (dashed line, not a taxonomic structure).

FIGURE 4. An Environmental Scanning Electron Microscope (ESEM) photograph of the four main structures of the apical plate of the endophallus within the penis lobe. This is an example from Mecodema haunoho showing the central spicule (c.s), left (l.s.f) and the right setose flange (r.s.f), and microtrichial field (m.f). These structures are variable among species but within a species, they are very consistent, even over distant geographical ranges. The microtrichial field can be covered in flattened scales as in photo above, or with elongated setae-like scales.

FIGURE 6. Detail of the three different forms of the elytral humeral angle: (A) = anteriorly convergent (M. parataiko), (B) = evenly convex (M. oconnori), (C) = subangulate (M. atuanui).

FIGURE 9. Dorsal view of head with detail of the morphological structures used in the species descriptions. Ƒ = vertex; SPS = supraorbital puncture setae; SP = supraorbital puncture; F = frons area; FCS = frontoclypeal suture; C = clypeus; M = mandible; LS = labrum setae; L = labrum; ACM = anterior clypeal microsculpture; CSP = clypeal setose puncture; TP = tentorial pit; SG = supraorbital grooves; E = eye; ƑG = vertexal groove.

FIGURE 10. The protibia form is a character used mainly to determine between genera, except for one species in Mecodema where the difference between (A) greatly distally expanded (M. antarctica) and (B) expanded distally (all other Mecodema species) is used.

FIGURE 11. Detail of pronotum showing the taxonomic structures used in the species descriptions. PPC = posterior pronotum constriction; PS = pronotal setae; PAA = pronotum anterior angle; AE = anterior edge; PC = pronotal carina; ML = midline; PF= pronotal foveae; PPS = pronotum posterior sinuation; PE = posterior edge.

FIGURE 12. Ventral view of the mentum with a number of different character states. Illustrations A–D are the different forms of the indentation in the apex of the median process: (A) distinctly indentate (M. manaia); (B) moderately indentate (M. pluto); (C) slightly indentate (M. infimate); (D) indentation notched (M. parataiko). Illustrations E–G are the three general forms (i.e., hashed lines) of the mentum lobes: (E) triangular; (F) rounded; (G) squared.

FIGURE 14. Diagrammatic cross sections that represent the width and convexity of head or deflection of pronotum (frontal view): (A) broad and flat; (B) broad and convex; (C) narrow and flat; (D) narrow and convex.

FIGURE 15. The penis lobe in ventral view showing the relative deflection to right of vertical: (A) distinctly deflected (M. regulus); (B) moderately deflected (M. haunoho); (C) slightly deflected (M. oregoides). Scale bars = 1 mm. Structures of penis lobe indicated are: base (B); lateral edge (LE); apical portion (AP); ventral edge (ƑE).

FIGURE 16. Relative strength of the ventral curve over the length of the penis lobe (lateral view): (A) slightly curved (M. oblongum); (B) moderately curved (M. ponaiti); (C) distinctly curved (M. manaia). Scale bar = 1 mm.

FIGURE 31. Mecodema hector plate with half habitus (left) and the three (detached) structures of the male aedeagus: the right (RP) and left parameres (LP), plus the penis lobe (PL). The bottom scale bar is the width across the widest point of the pronotum of the specimen used for this habitus and top scale bar equates to the half the length of the penis lobe.