Mecodema mohi, Seldon & Buckley, 2019

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 : 71-74

Mecodema mohi sp. n.

Figure 38 .

Diagnosis: Mecodema mohi is different from other North Island Mecodema species by having: 1, vertexal groove very shallow and broad, defined laterally by sparse punctures, medially usually without microsculpture; 2, pronotum disc with distinct, small depressions either side of midline medially, some may have punctures close to pronotal foveae; 3, distinctive shape of the apical portion of the penis lobe ( Fig. 38 PL).

Description: Length 28–34.8 mm, pronotal width 7.5–9.93 mm, elytral width 8.4–11.5 mm. Colour of entire body matte to glossy black, coxae and femur may be bright red to dark reddish-brown.

Head: Very broad and flat. Vertex ( Fig. 9 ) with fine lines forming an isodiametric pattern laterally; vertexal groove very shallow and broad, defined laterally by sparse punctures ( Fig. 38 ), medially usually without microsculpture; large supraorbital puncture bearing 6–7 setae; 2 poorly defined supraorbital grooves; frons slightly convex medially; frontoclypeal suture indistinct, tentorial pits ( Fig. 9 ) small; anterior area of clypeus with broad and shallow grooves (may be indistinct), 1 large setose puncture each side bearing 2–3 setae ( Fig. 38 ), central puncture bearing 2 setae (may be absent). Labrum rectangular, anterior edge straight with 2 proximate central setae, 2 setae each side evenly spaced (may have an extra pair). Mentum lobes rounded ( Fig. 12F ), median process very short and broad, strongly angled upward (60°), distinctly indentate ( Fig. 12A ); mentum setae absent. Submentum sclerite constriction broad with 6–8 widely spaced setae. Stipes with 2 basal setae. Gula pits small, suture defined, gula flat with lines variably present or absent. Gena ( Fig. 8 ) with rugose wrinkles forming an isodiametric pattern across entire area.

Prothorax: Prothoracic carina broad the entire length, slightly crenulated with 8–15 setae each side ( Fig. 38 ), extended beyond anterior angle; posterior lateral sinuation ( Fig. 11 ) evidently carinate, slightly angled inward; pronotum broad and flat, overall shape broadly cordate; midline well-defined, anterior medial triangular impression and posterior medial diamond-shaped impression present, disc with fine transverse wrinkles extended laterally ( Fig. 38 ), distinct small depressions either side of midline medially, some specimens may have punctures proximate foveae; pronotal foveae broad and deep; anterior and posterior edges relatively straight. Prosternum flat with very fine transverse lines, anterior edge ridged; proepisternum microsculpture absent. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Broad and moderately deflected laterally; humeral angle evenly convex ( Fig. 6B ); basal margin moderately curved and gently sloped to base, interval 1 extended to scutellum; lateral carina ( Fig. 11 ) narrow the entire length, extended to humeral angle; humerus with 4–5 setose punctures, varying distribution along angle (asymmetrical) ( Fig. 38 ); suture impressed; striae 1–4 impressed with very small obsolescent punctures, striae 5–8 with punctures visibly present, all punctures small and regularly distributed; intervals 1–4 flat, intervals 5–8 moderately convex, interval 9 strongly convex; interval microsculpture present as transverse lines; 7 th strial setal pattern with 3–4 setose punctures in anterior ½, 4–5 setose punctures in posterior ½, setose punctures large.

Ventral surface: Mesepisternum sparsely punctured; metepisternum without microsculpture; setose punctures present on mesocoxae (2) and metacoxae (2). All abdominal ventrites finely lineate; ventrites 3–5 ( Fig. 2 ) with 1 setose puncture each side of midline; ventrite 6 with setae present: ♂ with 2–3 large setose punctures each side, apical edge straight between distantly spaced setae, ♀ with 3 large setose punctures each side, apical edge straight between distantly spaced setae; ventrites without lateral foveae. Anterior metaventrite process ( Fig. 2 ) an equalsided triangle with narrow and well-defined carina the entire length.

Male genitalia: Apical portion of penis lobe asymmetrically hooked with a slight deflection to right of vertical axis (VV) ( Fig. 15C ), apical portion narrow (60° angle in vertical plane), ventral process as pronounced as dorsal process ( Fig. 38 PL), ventral process a narrow and sharply rounded point, pushed forward of vertical axis ( Fig. 3 ), apex curved upward (flattened and symmetrical) to form slightly broadened dorsal process ( Fig. 38 PL), this is flattened (not recurved), brief curve returned to shaft; ventral edge of penis lobe curve to right distinct in apical ½ (VV), shaft narrowed slightly before apex but broadened to base, overall length of penis lobe distinctly curved ventrally (LV) ( Fig. 16C ). 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 with projection; setal (scales) coverage of the apical plate extensive (76–100%); size of left setose flange small; size of right setose flange very large. Left paramere basal lobe broadly triangular due to enlarged dorsal hump, moderately (45°) sloped to short and narrow arm; terminal lobe slightly broadened with tuft of long setae ( Fig. 38 LP); setae extended along apical portion to arm only; ventral edge straight. Right paramere narrowly triangular ( Fig. 38 RP), gradually narrowed to apex with a double row of long setae extended along apical ¾ of ventral edge.

Female genitalia: Basal gonocoxite 1 short and broad, apically flattened, ventral surface wrinkled with a few rugose grooves, internal dorso-lateral carina with 2 setae proximate base of gonocoxite 2, 1 seta double-spaced posterad (3 in total). Gonocoxite 2 ( Fig. 5 ) bluntly rounded and squatly triangular, apically reflexed. Ramus long and narrow.

Comments: Mecodema mohi is one of many similar large oconnori -like species inhabitating many North Island forest fragments. It is relatively abundant and can be easily found by rolling logs in Mohi Bush Scenic Reserve.

Distribution: New Zealand, North Island, Hawke’s Bay, Maraetotara Plateau, Mohi Bush S.R.

Holotype: NZAC male labelled. NEW ZEALAND, HB, Maraetotara Plateau , Mohi Bush S.R. By hand. 3 Jan 2015. D.S. Seldon, J.L. Druitt, K.G. Seldon / HOLOTYPE Mecodema mohi n. sp. design. DS Seldon, TR Buckley 2018 [red label].

Paratypes: 1♂, 2♀, New Zealand H.B. Mohi Bush Waimarama 10.XI.1985 T.H. and J.M. Davies / V / T.H. Davies Collection / AI.10473 ( NZAC) ; 4, NEW ZEALAND HB, Maraetotara Plateau , Mohi Bush S.R., 10 Dec 2012 – 7 Jan 2013, D.S. Seldon & D. Brown / pitfall traps, regen. podocarp-tawa canopy S39°51’24.5, E176°53’44.7 ( AMNZ) ; 1 [card mounted], Maraetotara Gorge , Hawkes Bay, 7.10.92, J.I. Townsend [hw] ( NZAC) .

Etymology: Mecodema mohi is named for the type locality (Mohi Bush S.R.).

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 3. Detail of the apical portion of aedeagus (male genitalia) with parameres removed showing taxonomic structures, vertical and horizontal planes that are referred to in the species descriptions and redescriptions: aedeagus shaft width (ASW); vertical central line (ƑCL) [dashed line, not a structure]; horizontal central line (HCL) [dashed line, not a 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 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 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 38. Mecodema mohi 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.