Mecodema ponaiti 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 : 95-97

Mecodema ponaiti Seldon & Leschen, 2011 .

Figures 16B and 48 .

Diagnosis: Differing from other North Island Mecodema species by: 1, the prothoracic carina with 4–6 setae along each side ( curvidens species group); 2, submentum sclerite with 2 setae widely-spaced each side; 3, shape of the basal lobe of the left paramere ( Fig. 48 LP).

Description: Length 20–26 mm, pronotal width 6.1–6.9 mm, elytral width 7.2–8.6 mm. Colour of the entire body glossy black, ventrally and legs may be dark reddish-brown.

Head: Narrow and flat, deflected laterally ( Fig. 14C ). Vertex smooth; vertexal groove medially narrow and broad laterally; large supraorbital puncture bearing 3–4 setae; 2–3 well-defined supraorbital grooves; frons smooth ( Fig. 48 ); frontoclypeal suture well-defined, tentorial pits large; anterior area of clypeus with indistinct and broad grooves, 1 setose puncture each side bearing 2 setae (or 2 setose punctures on each side bearing a single seta each). Labrum rounded, anterior edge slightly emarginated with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes squared ( Fig. 12G ), median process short and narrow, slightly angled upward (15°), weakly indentate ( Fig. 12C ); mentum setae present. Submentum sclerite constriction broad with 2 setae widely-spaced medially, 2 setae widely-spaced each side. Stipes with 2 basal setae. Gula pits large, suture defined, gula flat and smooth. Gena ( Fig. 8 ) with a fine isodiametric pattern across entire area.

Prothorax: Prothoracic carina broad the entire length, crenulations absent with 4–6 setae each side ( Fig. 48 ), extended to anterior angle (or extending to beyond anterior angle); posterior sinuation evidently carinate, parallel; pronotum narrow and moderately deflected laterally, overall shape rounded ( Fig. 48 ); midline well-defined, anterior medial impression absent, posterior medial diamond-shaped impression present, disc without microsculpture; pronotal foveae shallow and narrow; anterior edge strongly inwardly curved, posterior edge straight. Prosternum flat with evenly spaced, fine transverse lines; proepisternum without microsculpture. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Narrow and moderately delected laterally, overall shape ovate ( Fig. 48 ), posterior ⅓ steeply angled to apex; humeral angle anteriorly convergent ( Fig. 6A ) (enhancing ovate shape); basal margin moderately curved and bevelled to base, interval 1 extended to scutellum; lateral carina narrow the entire length, extended to humeral angle; humerus with 2 widely-spaced setose punctures; suture impressed; all striae with small, regularly distributed, asetose punctures (in some specimens striae punctures may be partially obsolescent); all intervals weakly convex, interval 9 truncated and broadened; interval microsculpture present as fine lines; 7 th strial setal pattern with 1–2 setose punctures in anterior ½, 4–5 setose punctures in posterior ½ ( Fig. 48 ), setose punctures large.

Ventral surface: Mesepisternum and metepisternum ( Fig. 2 ) without microsculpture; setose punctures present on mesocoxae (1) and metacoxae absent. All abdominal ventrites finely lineate laterally; ventrites 3–5 without setose punctures each side of midline; ventrite 6 setae present: ♂ with 3 very proximate setose punctures grouped each side at junction of straight apical edge and curve anterad, ♀ with 2 setose punctures each side widely spaced on bluntly pointed apical edge; some ventrites laterally foveate (indistinct). Anterior metaventrite process ( Fig. 2 ) a short, pointed triangle with a broad carina the entire length.

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 narrow and straight the entire length (VV) ( Fig. 48 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 short 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 narrowly rectangular without dorsal hump ( Fig. 48 LP), moderate slope (45°) to arm; arm long and broad, gradually narrowed to terminus; terminal lobe indistinct from arm, apical tuft of sparse long setae, sparsely distributed, short-lengthed setae extended along apical ½ of ventral edge ( Fig. 48 LP); ventral edge straight. Right paramere narrowly triangular, gradually narrowed to terminus with a double row of mediumlengthed setae extended along apical ¾ along of ventral edge ( Fig. 48 RP).

Female genitalia: Basal gonocoxite 1 long and narrow, apically broadened, ventral surface with a few rugose wrinkles, internal dorso-lateral carina with 2 setae. Gonocoxite 2 ( Fig. 5 ) ovate. Ramus long and broad.

Comments: Mecodema ponaiti is endemic to the Poor Knights Islands and is more closely related to M. regulus from the Three Kings Islands, than the nearest mainland species ( Seldon & Leschen 2011).

Distribution: New Zealand, North Island, Northland, Poor Knights Islands (only).

Holotype: NZAC male labelled. NEW ZEALAND ND Poor Knights Is. Tawhiti Rahi Is. 18 Dec 2009 D.S. Seldon, R.A.B. Leschen & T. Buckley / HOLOTYPE Mecodema ponaiti n. sp. design. by Seldon & Leschen 2010 [red label].

Paratypes: (see Seldon & Leschen 2011).

Material examined: 1♂, NEW ZEALAND, ND, Tawhiti Rahi , Poor Knights Isl., 10 Dec 2013, T.R. Buckley, S. Myers, J. Stavert, TB781, ex rotting log, 35 26.990 S, 174 44.154 E, 145 m / CAR127 ( NZAC) ; 1♀, NEW ZEALAND, ND, Tawhiti Rahi , Poor Knights Isl., 31 Oct 2004 F. Brook ( NZAC) .

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 8. Detail of the ventral head with the taxonomic structures used in the species descriptions. SBMS = submentum setae; SBM = submentum sclerite; ML = mentum lobe; MP = mentum process (with indentation); MPW = mentum process width; SBS = stipes basal setae; MPL = mentum process length; MPS = mentum process setae; SBMC = submentum sclerite constriction; GP = gula pits; GS = gula suture.

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 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 48. Mecodema ponaiti 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.