Mecodema dunnorum, 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 : 41-42

Mecodema dunnorum sp. n.

Figure 25 .

Diagnosis: Differing from other North Island Mecodema species by: 1, vertexal groove shallow, more impressed laterally, unpunctured, but large dimples laterally; 2, prothoracic carina broad the entire length, smooth with 14–17 setae along each side; 3, distinctive shape of apical portion of the penis lobe ( Fig. 25 PL).

Description: Length 28.8–30.5 mm, pronotal width 8–8.5 mm, elytral width 9–9.7 mm. Colour of entire body matte to glossy black, except reddish hues variably present ventrally.

Head: Broad and flat ( Fig. 14A ). Vertex ( Fig. 9 ) with very fine wrinkles laterally; vertexal groove shallow, more impressed laterally but with large dimples laterally; large supraorbital puncture bearing 3–4 setae ( Fig. 25 ); 4–5 well-defined supraorbital grooves anterad eyes; frons micropunctate extended onto vertex, a broad and shallow depression each side of midline, small transverse lines laterally; frontoclypeal suture indistinct with very small tentorial pits; anterior area of clypeus ( Fig. 9 ) with 2 long, narrow grooves, short central groove with 1 setose puncture bearing 1–2 setae, 1 setose puncture each side of bearing 1–2 setae. Labrum lobate, anterior edge slightly emarginated with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded ( Fig. 12F ), median process broad and short (squat), slightly angled upward (15°), moderately indentate ( Fig. 12B ); mentum setae absent. Submentum sclerite constriction narrow with 6–8 evenly distributed setae. Stipes with 2 basal setae. Gula pits small, suture poorly defined, gula flat with fine transverse lines. Gena ( Fig. 8 ) with a fine isodiametric pattern across entire area.

Prothorax: Prothoracic carina broad the entire length, crenulations absent with 14–17 setae each side ( Fig. 25 ), extended beyond anterior angle; posterior lateral sinuation short, evidently carinate, parallel; overall shape cordate, broad and deflected laterally; midline indistinct, anterior medial triangular impression and posterior medial diamond-shaped impression present, disc with very fine transverse wrinkles across entire surface, a distinct small and round depression either side at midway (observable by naked eye); pronotal foveae broad and shallow; anterior and posterior edges straight ( Fig. 25 ). Prosternum flat with transverse lines, a shallow depression each side; proepisternum without microsculpture. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Broad and slightly deflected laterally, posterior end of elytra steep to apex; humeral angle evenly convex ( Fig. 6B ) with a pronounced, rounded carina (looks squared to naked eye); basal margin slightly curved and gently sloped to bevelled laterally to base, interval 1 extended to scutellum; lateral carina narrow, broadened slightly in posterior ⅓, extended beyond humeral angle; humerus with 3 evenly spaced setose punctures proximate the angle, 1 setose puncture triple-spaced posterad; suture well-defined and concave; intervals 1–3 flat or slightly convex, convexity increased laterally, intervals 7–9 strongly convex entire length; interval microsculpture absent; striae defined by small, regularly spaced asetose punctures entire length, striae 1–4 maybe obsolescent; 7 th stria setal pattern with 3 setose punctures in anterior ½, 5 setose punctures in posterior ½ ( Fig. 25 ), setose punctures large.

Ventral surface: Mesepisternum and metepisternum ( Fig. 2 ) without microsculpture; setose punctures present on mesocoxae (2) and metacoxae (2–3). Abdominal ventrites 1–5 finely lineate; ventrites 3–5 with very shallow lateral depressions, 1 setose puncture each side of midline; ventrite 6 setae present: ♂ with 1–2 setose punctures each side at junction of straight apical edge and curve anterad, (no ♀ specimen available). Anterior metaventrite process ( Fig. 2 ) a triangle with a broad carina the entire length.

Male genitalia: Apical portion of penis lobe asymmetrically double-hooked with a moderate deflection to right of vertical axis (VV) ( Fig. 15B ); apical portion broad (LV), ventral process formed by ventral edge (of shaft) curving downward to form a short, symmetrically rounded point, medial point is slightly back from vertical axis ( Fig. 25 PL), apex curved upward in a broad asymmetrical curve to form dorsal process, that is broad at the base, short and rounded but slightly recurved posterad, a brief and even curve to the shaft ( Fig. 25 PL); penis lobe shaft with narrow apical portion broadened gradually to base; apical ⅓ of shaft moderately curved to right (VV), overall penis lobe is moderately curved ventrally (LV) ( Fig. 16B ). Structures of the endophallus ( Fig. 4 ): lateral form of the apex of the central spicule flattened; dorsal form of the apex of the central spicule greatly expanded without projection; setal (scales) coverage of the apical plate moderate (26-75%); size of left setose flange small; size of right setose flange distinctly large (long). Left paramere basal lobe at right angle of articulation large and short (compared to right paramere), rectangular with slight dorsal hump forming moderate slope (45°) to a very short, truncated arm ( Fig. 25 LP), larger terminal lobe; tuft of medium length setae situated at the apex of the terminal lobe and ventral upward curve of basal lobe-arm junction, setae shorten to end of curve; anterior edge of basal lobe curved downward, setae absent ( Fig. 25 LP); ventral edge straight. Right paramere longer than left paramere, rectangular with slope to small terminal lobe ( Fig. 25 RP) with a double-row of long setae extended along apical ¾ of ventral edge.

Female genitalia: no female specimen available.

Comments: Mecodema dunnorum is restricted to a small number of native forest fragments south of the Puhoi River in the Puhoi Valley, north Auckland.

Distribution: New Zealand, North Island, AK, Remiger’s Bush S.R. (Puhoi), south of the Puhoi River.

Holotype: NZAC male labelled. NEW ZEALAND AK, Puhoi , Remiger’s Bush S.R., podocarp-broadleaf forest within 50 m of stream, 28 Nov–18 Dec 2013. D.S. Seldon DSS095 / pit traps 36°30’02.6S, 174°37’22.1E, 40 m / HOLOTYPE Mecodema dunnorum n. sp. design. DS Seldon, TR Buckley 2018 [red label].

Paratypes: 1♂, NEW ZEALAND AK, Puhoi, Remiger’s Bush S.R., podocarp-broadleaf forest within 50 m of stream, 28 Nov–18 Dec 2013. D.S. Seldon DSS095 / pit traps 36°30’02.6S, 174°37’22.1E, 40 m, CAR 114 ( NZAC) ; 1♂, NEW ZEALAND AK, Puhoi, Remiger’s Bush S.R., podocarp-broadleaf forest within 50 m of stream, 28 Nov–18 Dec 2013. D.S. Seldon DSS095 / pit traps 36°30’02.6S, 174°37’22.1E, 40 m, CAR 195 ( AMNZ) .

Etymology: The species name, Mecodema dunnorum , honours Valerie and the late Arthur Dunn, QSM for the numerous community activities and conservation work (including bequeathing land to the Queen Elizabeth II National Trust) that they were, and have been involved in around the Puhoi-Warkworth area.

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 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 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 25. Mecodema dunnorum 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.