Mecodema ngaitahuhu, 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 : 78-79

Mecodema ngaitahuhu sp. n.

Figure 41 .

Diagnosis: Distinguished from other North Island Mecodema species because: 1, the prothoracic carina is smooth with 7–11 setae each side; 2, elytral interval 6 is truncated, i.e. it terminates before meeting the basal margin; 3, distinct shape of the apical portion of the penis lobe ( Fig. 41 PL); 4, form of the left paramere terminal lobe and ventral edge setae ( Fig. 41 LP).

Description: Length 26–32 mm, pronotal width 7.5–9.5 mm, elytral width 8.6–10.6 mm. Colour of entire body matte to glossy black dorsal, ventrally may be dark reddish-brown, including coxae and legs.

Head: Broad and flat ( Fig. 14A ). Vertex smooth; vertexal groove shallow, defined laterally by indentations (obsolescent punctures); large supraorbital puncture bearing 5 setae ( Fig. 41 ); 2–3 supraorbital grooves poorly defined mesad eyes; frons smooth; frontoclypeal suture indistinct, tentorial pits very small; anterior clypeus with well-defined grooves, 1 setose puncture each side bearing 1–2 setae (may have central setose puncture bearing 1 seta). Labrum lobate, anterior edge strongly emarginated with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded ( Fig. 12F ), mentum process broad and very broad, slightly angled upward (15°), distinctly indentate ( Fig. 12A ); mentum setae variably present or absent. Submentum sclerite ( Fig. 8 ) constriction narrow with 6 setose punctures, wide gap medially, then setae evenly spaced. Stipes with 2 basal setae. Gula pits small within defined suture, gula flat and smooth. Gena with fine lines forming an isodiametric pattern across entire area.

Prothorax: Prothoracic carina broad at shoulder, narrowed to sinuation, smooth to slightly crenulated with 7–11 setae each side ( Fig. 41 ), extended beyond anterior angle; posterior sinuation indistinctly carinate, parallel; pronotum broad and flattened but deflected laterally, anterior lateral margin rounded, overall shape cordate; midline well-defined, anterior medial and posterior medial diamond-shaped impressions present, disc entirely covered with fine transverse lines ( Fig. 41 ); pronotal foveae broad and shallow; anterior edge relatively straight, posterior edge curved inwardly medially. Prosternum flat with transverse wrinkles; proepisternum without microsculpture. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Broad and moderately deflected; humeral angle evenly convex ( Fig. 6B ); basal margin slightly curved and gently sloped to base, interval 1 extended to scutellum; lateral carina narrow the entire length, extended to humeral angle; humerus with 3–4 setose punctures, 3 proximate and 1 double-spaced posterad ( Fig. 41 ); suture well-defined; all striae with regularly spaced, asetose punctures, striae 1–4 defined by very small asetose punctures, striae 5–8 defined by slightly larger asetose punctures; intervals 1–4 flat to weakly convex, intervals 5–8 moderately convex, interval 6 terminated prior to basal margin; interval microsculpture present as fine lines; 7 th strial setal pattern with 3–4 setose punctures in anterior ½, 4–5 setose punctures in posterior ½ ( Fig. 41 ), setose punctures large.

Ventral surface: Mesepisternum ( Fig. 2 ) micropunctate and shallowly grooved; metepisternum with finely lineate; setose punctures present on mesocoxa (2) and metacoxa (2–3). Abdominal ventrite 1 without microsculpture, ventrite 2 finely lineate and finely pitted, ventrites 3–5 with 1 setose puncture each side of midline and finely lineate laterally; ventrite 6 setae present ( Fig. 2 ): ♂ with 1 setose puncture each side at junction of straight apical edge and curve anterad, ♀ with 2–3 setose punctures each side, along rounded apical edge; ventrite 2 foveate laterally (shallow). Anterior metaventrite process a pointed triangle with an apically broad, narrowed posterad carina.

Male genitalia: Apical portion of penis lobe asymmetrically hooked with a slight deflection to right of vertical axis (VV) ( Fig. 15C ); apical portion narrow entire width (vertical plane), ventral process short and sharply pointed ( Fig. 41 PL), apex upward curve symmetrical to form a long, narrow and bluntly rounded (almost flat) dorsal process with a short and flat recurve to shaft ( Fig. 41 PL); shaft of penis lobe with moderate curve to right (ventral edge), especially apically (VV); penis lobe shaft narrow, overall length 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 (76–100%); size of left setose flange small; size of right setose flange absent. Left paramere basal lobe narrowly rectangular with large dorsal hump forming a steep slope (60°) to arm ( Fig. 41 LP); arm broad and short; terminal lobe short and narrowed with apical tuft of dense long setae; ventral edge straight with a comb of short to mediumlengthed setae sparsely distributed from mid-arm to mid-basal lobe ( Fig. 41 LP). Right paramere long and narrowly triangular with a double row of long setae extended along apical ¾ of ventral edge ( Fig. 41 RP).

Female genitalia: Basal gonocoxite 1 short and broad, internal dorso-lateral carina with 1 seta, ventral surface with rugose grooves across entire area. Gonocoxite 2 short, rounded and triangular, apically refexed. Ramus ( Fig. 5 ) short and narrow.

Comments: There are a number of large Mecodema species in the Whangarei to Dargaville area; almost each mountain in the vicinity has a unique species.

Distribution: New Zealand, North Island, Northland, Tangitoria, Tangihua Forest.

Holotype: NZAC male labelled. NEW ZEALAND ND, Tangihua For., River Tk. , PTs, DSS074 6–21 Dec 2012, DS Seldon, CAR247 / Regen. kauri-podocarp-broadleaf canopy , S35°53’06.7, 174°07’34.5, ca 86 m / HOLOTYPE Mecodema ngaitahuhu n. sp. design. DS Seldon, TR Buckley 2018 [red label].

Paratypes: 1, 1♀, NEW ZEALAND ND, Tangihua Forest , River Tk, PTs, 1 Feb 2013, DS Seldon / podocarpbroadleaf forest, within ca 50 m of river , CAR 216 ♀ ( NZAC) .

Etymology: This species is named for Ngai Tahuhu, whose rohe includes Tangihua Forest. Ngai Tahuhu were driven from their land during the mid-18th century by the Ngapuhi chiefs Te Ponaharakeke and Te Ngarokiteuru, who joined forces to accomplish this feat.

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 41. Mecodema ngaitahuhu 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.