Mecodema atuanui, 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 : 32-34

Mecodema atuanui sp. n.

Figures 6C and 21 .

Diagnosis: Distinguished from other North Island Mecodema species by having: 1, a lobed labrum; 2, vertexal groove defined by punctures along the entire length; 3, elytral intervals 3 and 5 significantly broadened than other intervals; 4, the distinctively narrow width of the apical portion of the penis lobe ( Fig. 21 PL).

Description: Length 24.9 mm, pronotal width 6.7 mm, elytral width 7.9 mm. Colour of entire body matte black, except coxae and legs dark reddish-brown.

Head: Broad and flat ( Fig. 14A ). Vertex with very faint wrinkles; vertexal groove shallow, broadened laterally with several punctures present along groove; small supraorbital puncture bearing 2–3 setae (specimen damaged); 4 well-defined supraorbital grooves form a ridge anterad eye, grooves extended to lateral margins of frons; frons ( Fig. 9 ) with a ridge medially, a broad and shallow depression each side of midline extended to tentorial pits; frontoclypeal suture very narrow, cuticle humped anterad and posterad suture, tentorial pits small; anterior area of clypeus with 3 narrow grooves; clypeus with 1 large setose puncture each side bearing 2 setae. Labrum lobate, anterior edge distinctly emarginate medially with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded ( Fig. 12F ), median process short and broad, slightly angled upward (15°), indentation notched ( Fig. 12D ); setose punctures absent. Submentum sclerite constriction broad with 6 regularly spaced setae. Stipes with 2 basal setae. Gula ( Fig. 8 ) pits small, suture well-defined, anterior area of gula slightly convex, posterior flat and smooth. Gena with fine wrinkles forming an isodiametric pattern across entire area.

Prothorax: Prothoracic carina ( Fig. 11 ) broad in anterior ⅓, narrowed posterad, slightly crenulated with 7–10 setae each side, extended beyond anterior angle; posterior lateral sinuation evidently carinate, parallel; pronotal lateral margin broad, anterior lateral margin angled backward, deflected laterally, overall shape cordate; midline well-defined, posterior medial diamond-shaped impression present, disc with fine transverse wrinkles; pronotal foveae shallow and narrow; anterior edge and posterior edge straight ( Fig. 21 ). Prosternum flat and smooth; proepisternum obsolescently micropunctate. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Narrow and medially flattened; humeral angle subangulate ( Fig. 6C ), basal margin moderately curved and bevelled to base laterally, interval 1 extended to scutellum, all other intervals and striae truncated at margin; lateral carina narrow the entire length, broadened apically, extended to humeral angle; humerus with 3 setose punctures proximate the angle, 4 th double-spaced posterad ( Fig. 21 ); suture defined but no more so than striae; striae 1–6 with asetose punctures poorly defined, striae 7 and 8 with asetose punctures visible in posterior ½ only; intervals 1–4 weakly convex, convexity of intervals 5–8 increased laterally; interval microsculpture present as short fine transverse lines radiating from asetose punctures, increased in intensity laterally; intervals 3 and 5 significantly broader than other intervals; 7 th strial setal pattern ( Fig. 1 ) with 3 setae in anterior ½ and 3 setae in posterior ½, a relatively large space between setose punctures medially ( Fig. 21 ), setose punctures small.

Ventral surface: Mesepisternum without microsculpture; metepisternum ( Fig. 2 ) with finely lineate proximate carina; setose punctures present on mesocoxae (1) and on metacoxae (2). Abdominal ventrites 1–5 finely lineate; ventrites 3–5 with 1 setose puncture each side of midline; ventrite 6 setae present: ♂ with 1 seta each side situated at postero-lateral angle, apical edge straight (no ♀ specimen available); lateral foveae on ventrites absent. Anterior metaventrite process ( Fig. 2 ) a short triangle with a very well-defined broad carina the entire length.

Male genitalia: (both parameres have lost parts of the setal fringes).

Apical portion of penis lobe asymmetrically hooked, short apical portion with moderate deflection to right of vertical axis (VV) ( Fig. 15B ), ventral edge of penis lobe straight (VV); apex width entirely narrow, ventral process sharply angled to a rounded point ( Fig. 21 PL), the point is slightly forward of perpendicular ( Fig. 3 ), apex curved upward to form the dorsal process that is very rounded ( Fig. 21 PL), broad at base, hook posterad perpendicular; shaft of penis lobe narrow, slightly broadened apically, overall length of penis lobe 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 with a projection; setal (scales) coverage of apical plate is extensive (76–100%); left setose flange large; right setose flange absent. Left paramere basal lobe rectangular with an anterior hump forming a moderate (45°) slope to arm; arm narrow and broadened to form terminal lobe ( Fig. 21 LP); setae extended to basal lobe-arm junction (apical ⅓) with tuft of short setae at apex of lobe; ventral edge relatively straight. Right paramere broadly triangular but not as high at apex ( Fig. 21 RP), double-row of long setae extended along apical ½ of ventral edge; apical ⅓ of right paramere inwardly curved in front of penis lobe posterad apical hook.

Female genitalia: no female specimen available.

Comments: Mecodema atuanui is more closely related to M. spiniferum (Waitakere Ranges) , than species to the north ( M. rusticulus ) or east ( M. dunnorum ).

Distribution: New Zealand, North Island, Auckland region, Kaipara Harbour Coast (south of the Hoteo River), Mt Auckland (Atuanui).

Holotype: AMNZ male labelled. NEW ZEALAND, AK, Atuanui ( Mt Auckland), pitfall D13, Jan 2002, A. Warren / HOLOTYPE Mecodema atuanui n. sp. design. DS Seldon, TR Buckley 2018 [red label] / AMNZ 57759 [green label] .

Etymology: The species is named after the only known locality, Atuanui (Mt Auckland), where a single specimen has been collected.

Figures

FIGURE 1. Dorsal view of a Mecodema specimen showing taxonomic structures used in the species descriptions. H =head; P = pronotum; E = elytra; S = striae; I1 = interval 1; A = apex; 7S = 7 th strial setae; HSP = humerus setose puncture; HA = humeral angle; BM = basal margin; P = protibia.

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 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 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 21. Mecodema atuanui 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.