Mecodema aoteanoho Seldon & Leschen, 2011

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 : 25-27

Mecodema aoteanoho Seldon & Leschen, 2011 .

Figure 18 .

Diagnosis: Distinguished from other North Island Mecodema species by: 1, the prothoracic carina with 4–5 setae along each side ( curvidens species group); 2, elytral striae and intervals abruptly truncated at basal margin; 3, 7 th stria with 4 long setae, evenly distributed in posterior ½; 4, interval 8 truncated basally by humeral puncture, forming distinctive angle with interval 7.

Description: Length 19–24 mm, pronotal width 4.5–6 mm, elytral width 5.5–7 mm. Colour of entire body matte black, coxae and legs glossy black.

Head: Broad and convex ( Fig. 14B ). Vertex smooth; vertexal groove narrow and well-defined the entire length; small supraorbital puncture bearing 3 setae; a single narrow and large supraorbital groove anterad eye; frons with a broad and shallow depression each side of midline; frontoclypeal suture shallow but defined between very small tentorial pits; anterior area of clypeus with narrowly grooved; clypeus with 1 setose puncture on each side bearing 2–3 setae. Labrum rectangular, anterior edge straight with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes squared ( Fig. 12G ), median process narrow and short, upward angle absent, indentation notched ( Fig. 12D ); setose punctures present. Submentum sclerite constriction narrow with 6 very long, evenly spaced setae. Stipes with 2 basal setae. Gula pits small, suture indistinct, gula flat with a very fine isodiametric pattern. Gena with very fine transverse wrinkles (may be absent).

Prothorax: Prothoracic carina narrow the entire length, slightly crenulated with 4–5 setae each side ( Fig. 18 ), extended beyond anterior angle; posterior lateral sinuation indistinctly carinate, slightly angled inward; pronotum broad but moderately deflected laterally, overall shape squared (sides straight) ( Fig 18 ); midline defined in anterior half only, medial impressions absent, disc with transverse wrinkles laterally (may be absent); pronotal fovea ( Fig. 11 ) shallow and narrow; anterior edge slightly inwardly curved, posterior edge straight ( Fig. 18 ). Prosternum weakly convex and smooth; proepisternum ( Fig. 2 ) without microsculpture. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Narrow and laterally deflected; humeral angle anteriorly convergent ( Fig. 6A ); basal margin very slightly curved and steeply bevelled to base (striae and all intervals abruptly truncated at margin); lateral carina very narrow the entire length, extended to humeral angle; humerus with 2 large setose punctures near humeral angle ( Fig. 18 ); suture impressed, but not more so than striae; striae with regularly distributed, small, asetose punctures that increase slightly in size laterally; intervals 1–4 flat to weakly convex, convexity increased laterally; interval microsculpture absent; interval 8 truncated basally by humeral puncture, forming distinct angle with interval 7 ( Fig. 18 ); 7 th strial setal pattern with 4 long setae evenly spaced in posterior ½ (only in apical region), setose punctures small.

Ventral surface: Mesepisternum and metepisternum without microsculpture; setose punctures of mesocoxae and metacoxae absent. Abdominal ventrites 1–5 smooth; ventrite 6 setae present: ♂ with 1 setose puncture each side located of straight apical edge and curve anterad, ♀ with 2 evenly spaced setose punctures each side of midline along a bluntly rounded apical edge; lateral foveae absent. Anterior metaventrite process a triangle with a very broad carina, especially between metacoxae.

Male genitalia: Apical portion of penis lobe symmetrically rounded with a moderate deflection to right of vertical axis (VV) ( Fig. 15B ); shaft of penis lobe straight and narrow (VV) ( Fig. 18 PL), 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 rounded; dorsal form of the apex of the central spicule is narrow and short; setal (scales) coverage of the apical plate sparse (1–25%); left setose flange small; right setose flange large. Left paramere main body rectangular, slightly humped dorsally forming a gently sloped anterior angle (15°), angle very short and continued to form arm; arm broad and short (<half main body length); terminal lobe relatively small, apical tuft of long setae, with setation continuing along apical ½ of ventral edge ( Fig. 18 LP); ventral edge of main body straight. Right paramere only slightly smaller than left paramere, narrowly rectangular, arm relatively long (½ of length), setae extended along apical ¾ length of ventral edge with longer setae behind apical lobe ( Fig. 18 RP).

Female genitalia: Basal gonocoxite 1 short and broad, ventral surface entirely wrinkled, dorsal surface with a light scattering of sensillar pits; internal dorso-lateral carina with a single short apical seta. Gonocoxite 2 ( Fig. 5 ) paddle-like, bluntly rounded, ventral surface slightly convex with scattered sensilli, raised carina around edge. Ramus long and narrow, but broadened apically.

Comments: Mecodema aoteanoho is the first described carabid species that is endemic to Aotea (Great Barrier Island). It is the sister taxon M. haunoho (Te Hauturu-o-Toi/Little Barrier Island).

Distribution: New Zealand, North Island, Great Barrier Island (only).

Holotype: NZAC male labelled. NEW ZEALAND CL Great Barrier I 23–28 Mar 1978 ESNZ Field Trip / Whangaparapara Track x under logs [hw] / HOLOTYPE Mecodema aoteanoho n. sp. design. Seldon & Leschen 2011 [red label].

Paratypes: (see Seldon & Leschen 2011).

Figures

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 5. The entire female reproductive tract (ventral view) including taxonomic structures (for all other abbreviated structure names see Seldon et al. 2012). However, for this revision only the following structures are important: HS = helminthoid sclerite; G1 = gonocoxite 1; G2 = gonocoxite 2; TDC = transverse dorsal carina; R = ramus.

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 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 18. Mecodema aoteanoho 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.