Mecodema xylanthrax, 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 : 136-138

Mecodema xylanthrax sp. n.

Figure 65 .

Diagnosis: Distinguishable from other North Island Mecodema species due to the: 1, vertexal groove broad and shallow entire, marked with very short, slightly impressed grooves; 2, prothoracic carina broad in anterior ⅓, narrowed in posterior ¾, slightly crenulated with 8–9 setae each side; 3, distinct shape of the apical portion of the penis lobe ( Fig. 65 PL).

Description: Length 27.7–33.4 mm, pronotal width 7.9–9.3 mm, elytral width 8.8–10.5 mm. Colour of entire body matte to glossy black.

Head: Broad and flat ( Fig. 14A ). Vertex with very fine wrinkles; vertexal groove broad and shallow entire, marked with very short, slightly impressed grooves; small supraorbital puncture bearing 3–4 setae, 3 poorly defined supraorbital grooves; frons smooth ( Fig. 65 ), except indistinctly impressed, tranverse grooves posterad frontoclypeal suture; frontoclypeal suture ( Fig. 9 ) poorly defined, tentorial pits very small; anterior area of clypeus with very shallow grooves laterally and medially, 1 setose puncture each side bearing 1–2 setae ( Fig. 65 ), medial setose puncture bearing 2 setae (may be absent). Labrum rectangular, anterior edge outwardly curved, slightly emarginated with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded ( Fig. 12F ), median process broad and short, moderately angled upward (30°), distinctly indentate ( Fig. 12A ); mentum setae absent. Submentum sclerite constriction broad with 6 evenly distributed setae. Stipes with 2 basal setae. Gula pits small, suture well-defined, gula flat with very fine transverse lines. Gena ( Fig. 8 ) with very fine wrinkles forming an isodiametric pattern across entire area.

Prothorax: Prothoracic carina broad in anterior ⅓, narrowed in posterior ¾, slightly crenulated with 8–9 setae each side ( Fig. 65 ), extended to anterior angle; posterior lateral sinuation indistinctly carinate, parallel; pronotum broad and moderately deflected, overall shape cordate ( Fig. 65 ); midline well-defined, anterior medial and posterior medial diamond-shaped impressions present, may have small round depressions at anterior lateral margin, disc with fine transverse wrinkles laterally; pronotal foveae broad and shallow; anterior edge inwardly curved, posterior edge straight ( Fig. 65 ). Prosternum flat with a few transverse lines; proepisternum without microsculpture. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Broad and moderately deflected laterally; humeral angle anteriorly convergent ( Fig. 6A ) (accentuates narrow look of elytra); basal margin moderately curved and gently sloped to base, interval 1 extended to scutellum; lateral carina narrow the entire length, broadened in posterior ⅓, extended to humeral angle; humerus with 3 setose punctures, proximate the angle (1 may be double-spaced posterad) ( Fig. 65 ); suture poorly impressed; striae with small, regularly spaced, asetose punctures, striae 1–6 with obsolescent asetose punctures, striae 7–9 asetose punctures more defined; intervals 1–4 weakly convex, intervals 5–9 moderately convex; interval microsculpture absent; 7 th strial setal pattern with 2–3 setose punctures in anterior ½, 4–5 setose punctures in posterior ½ ( Fig. 65 ), setose punctures large.

Ventral surface: Mesepisternum ( Fig. 2 ) with a few shallow grooves; metepisternum without microsculpture; setose punctures present on mesocoxa (2) and metacoxa (2). All abdominal ventrites finely lineate laterally; ventrites 3–5 with 1 setose puncture each side of midline; ventrite 6 setae present: ♂ with 1 setose puncture at junction of straight apical edge and curve anterad, ♀ with 2 evenly spaced setose punctures each side along bluntly rounded apical edge; lateral foveae absent. Anterior metaventrite process a short and pointed triangle with carina apically broad to narrowed posterad.

Male genitalia: Apical portion of penis lobe asymmetrically disc-shaped ( Fig. 65 PL) with moderate deflection to right of vertical (VV) ( Fig. 15B ); ventral process a bluntly, rounded point on vertical axis ( Fig. 3 ), apex symmetrically curved to form dorsal process that is a broadly rounded and flatly curved twice height of ventral process ( Fig. 65 PL), sharp angle to shaft; apical ¼ of shaft of penis lobe curved to right (VV) ( Fig. 15A ), shaft narrow apically, gradually broadened toward base; 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 pointed; dorsal form of the apex of the central spicule greatly expanded with projection; setal (scales) coverage of the apical plate moderate (26–75%); size of left setose flange small; size of right setose flange very long. Left paramere basal lobe rounded triangular due to moderate anterior hump forming gradual (45°) slope to arm ( Fig. 65 LP); arm very short and narrow (½ length of terminal lobe), terminal lobe short and broad with apical tuft of short setae, sparsely distributed and very short setae along lobe and arm to fringe of longer setae in arm-basal lobe junction curve ( Fig. 65 LP), setae absent from ventral edge of basal lobe; ventral edge straight. Right paramere broadly triangular with a double row of setae extended along apical ¾ of ventral edge ( Fig. 65 RP); apical ¼ slightly inwardly curved toward penis lobe.

Female genitalia: Basal gonocoxite 1 short and broad, ventral surface with a few rugose grooves, internal dorso-lateral carina ( Fig. 5 ) with 2 setae. Gonocoxite 2 short, bluntly, rounded triangle, slightly recurved apically. Ramus long and broad.

Comments: Mecodema xylanthrax is found in the forested hills on the northern side of Waipu Gorge Rd, Northland. The range limits of this species are unknown.

Distribution: New Zealand, Northland, Waipu Gorge S.R., the western extent of the Brynderwyn Hills.

Holotype: NZAC male labelled. NEW ZEALAND ND Waipu Gorge, Waipu Gorge Sce. Res., 3605 S 17440 E, ca 150 m, 12. IX–15. X. 2001, Larivière.Larochelle / Wet taraire x nikau forest, along stream pittraps / HOLOTYPE Mecodema xylanthrax n. sp. design. DS Seldon, TR Buckley 2018 [red label].

Paratypes: 1♀, NEW ZEALAND, ND, Waipu Gorge Sce. Res. , 3605 S 17440 E, ca 150 m, 12. IX–15. X. 2001, Larivière.Larochelle / Wet taraire x nikau forest, along stream pittraps ( NZAC) ; 1♂, 3♀, NEW ZEALAND, ND, Waipu Gorge Sce. Res. , 3605 S 17440 E, ca 150 m, 12.XI.-10.XII. 2001, Larivière.Larochelle / Wet taraire x nikau forest, along stream pittraps ( NZAC) ; 1♀, NEW ZEALAND, ND, Waipu Gorge Sce. Res. , 3605 S 17440 E, ca 150 m, 10.XII.2001 – 14.I.2002, Larivière.Larochelle / Wet taraire x nikau forest, along stream pittraps ( NZAC); 1, NEW ZEALAND, ND, Brynderwyn’s, 28 Aug 1999, P.J. Anderson / NZMS 260 Q08 427 683, in leaf litter / AMNZ 40704 ; 1, MATAKANA, Nth Auck. , Oct 1959, VA Nicholls / AMNZ 84329 ; 1♂, NEW ZEALAND ND Waipu Gorge Sce Res 360SS 17440E ca 150m 15.X.–12.XI.2001 Larivière.Larochelle / wet taraire x nikau forest along stream ( NZAC) .

Etymology: Xylanthrax is a word meaning ‘coal’, and since this species of Mecodema and coal are both black in colour it is fitting.

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 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 65. Mecodema xylanthrax 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.