Mecodema spiniferum Broun, 1880

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 : 109-112

Mecodema spiniferum Broun, 1880 .

Figure 54 .

Diagnosis: Distinguishable from other North Island Mecodema species by: 1, having the pronotum a squaredcordate shape; 2, pronotal carina slightly crenulated; 3, elytra equally striate; 4, the apical portion of penis lobe distinctively shaped ( Fig. 54 PL).

Description: Length 25–31 mm, pronotal width 6.5–8.5 mm, elytral width 8–10 mm. Colour of entire body black, ventrites and legs may be reddish-brown.

Head: Broad and flat ( Fig. 14A ). Vertex smooth; vertexal groove shallow and broad the entire length with obsolescent punctures laterally ( Fig. 54 ); small supraorbital puncture bearing 3–5 setae; 4–5 shallow and narrow supraorbital grooves that extend onto anterior area of frons; frons medially convex (continues to posterior area of clypeus) with a small and shallow depression each side of midline; frontoclypeal suture a narrow groove, tentorial pits ( Fig. 9 ) are indistinct within a larger depression; anterior clypeus with 3 narrow grooves (laterally and medial), 1 large setose puncture each side bearing 2 setae ( Fig. 54 ), 1 medial setose puncture bearing 1 seta. Labrum lobate, anterior edge slightly emarginated with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded ( Fig. 12F ), mentum process very broad and short, slightly angled upward (15°), weakly indentate ( Fig. 12C ); mentum setae absent. Submentum sclerite constriction broad with 6–8 setae evenly spaced either side of large medial gap. Stipes with 2 basal setae. Gula pits narrow and deep, suture well-defined, gula flat with transverse rugose microsculpture. Gena ( Fig. 8 ) with a fine isodiametric pattern across entire area.

Prothorax: Prothoracic carina narrow the entire length, slightly crenulated with 10–14 setae each side (setae extended anterad edge of foveae), extended beyond anterior angle; posterior lateral sinuation evidently carinate, slightly angled inward; pronotum broad and deflected laterally, overall shape squared cordate ( Fig. 54 ); midline well-defined, anterior medial triangular impression and posterior medial diamond-shaped impression present, disc with very fine transverse lines laterally ( Fig. 54 ); pronotal foveae broad and shallow; anterior edge slightly inwardly curved, posterior edge straight. Prosternum flat with small round depressions each side posterad; proepisternum without microsculpture. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Broad (flattened across suture) but slightly deflected laterally; humeral angle anteriorly convergent ( Fig. 6A ); basal margin slightly curved and gently sloped to base, interval 1 extended to margin; lateral carina narrow the entire length, extended beyond humeral angle; humerus with 3–4 setose punctures (one may be doublespaced posterad) ( Fig. 54 ); suture depth similar to striae; all striae with very small, evenly sized and spaced, asetose punctures that may look like lines (may be more defined laterally); intervals 1–8 flat or weakly convex, interval 9 moderately convex; interval microsculpture present as fine lines; 7 th strial setal pattern with 2–3 setose punctures in anterior ½, 4–5 setose punctures in posterior ½ ( Fig. 54 ), setose punctures small.

Ventral surface: Mesepisternum and metepisternum ( Fig. 2 ) without microsculpture; setose punctures present on mesocoxa (2) and metacoxa (2). All abdominal ventrites finely lineate laterally, ventrites 3–5 with 1 (may be 2) setose puncture each side of midline; ventrites foveate (very shallow) laterally; ventrite 6 setae present: ♂ with 1 setose puncture each side at junction of straight apical edge and curve anterad, ♀ with 2 setose punctures each side, evenly-spaced along rounded apical edge. Anterior metaventrite process ( Fig. 2 ) long, narrowly triangular with a well-defined and narrow carina the entire length.

Male genitalia: Apical portion of penis lobe asymmetrically hooked (overall width of apex narrow) with a distinct deflection to right of vertical axis (VV) ( Fig. 15A ); ventral process slightly forward of centre of vertical axis ( Fig. 3 ); ventral edge of shaft curved downward to form a relatively broad, rounded point of ventral process, apex curved asymmetrically upward to form dorsal process ( Fig. 54 PL), a short and rounded hook, slightly recurved posterad, brief and sharp curve to shaft; penis lobe shaft straight (VV); penis lobe shaft narrow the entire length, overall length of penis lobe definitely 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 without projection; setal (scales) coverage of the apical plate sparse (1–25%); size of left setose flange small; size of right setose flange large. Left paramere basal lobe large and rectangular with a dorsal hump forming a steeply angled (60°) slope to arm; arm narrow and short ( Fig. 54 LP); terminal lobe broad and short (slightly broader dorsally than arm) with apical tuft of sparse medium-lengthed setae ( Fig. 54 LP), continued to basal lobearm junction curve, where a comb of long setae is located within curve, very few short setae along ventral edge; setae extended along apical ½ of straight ventral edge ( Fig. 54 LP). Right paramere narrowly triangular with a double row of long setae extended along apical ½ of ventral edge, apical ⅓ inwardly curved toward penis lobe ( Fig. 54 RP).

Female genitalia: Basal gonocoxite 1 short and broad, ventral surface with a few rugose wrinkles, internal dorso-lateral carina ( Fig. 5 ) without setae. Gonocoxite 2 bluntly, rounded and triangular, exterior edge straight. Ramus short and broad.

Comments: The Waitakere Ranges species was described by Broun (1880) from one mangled specimen and based on external characters only. Britton (1949) added more external characters, plus the male genitalia characters, but the illustration of the aedeagus does not match the species ( M. spiniferum ) found in the Waitakere Ranges.

Distribution: New Zealand, North Island, Auckland, Waitakere Ranges, Riverhead Forest.

Holotype: BMNH specimen labelled. Type [round label with red border] / 22 / New Zeal. Broun Coll. Brit. Mus. 1922-482 / Waitakerei / Mecodema spinifer [hw].

Material examined: 1, Ex Decayed wood, 2 Sept. 62, Coll. M.B. Paterson / Fairy Falls Track, Waitakere Ranges, Auckland, N.I. / M.B. Paterson Collection / AMNZ 40722 (AMNZ); 1, Ranges, Auckland, N.I. / M.B. Paterson Collection / AMNZ 40721; 1, Waitakere , 11.9.32, A.T. P., Auck. Mus. Coll. / C.E. Clarke Collection / AMNZ 40727 ( AMNZ) ; 1, NEW ZEALAND, AK, Waitakere Ranges 20 m, 21 iv 1999, A. Blom, in garden L6894 / AMNZ 40726 ; 1, Waitakeries (SWANSON), R. Taylor, 15 May 1953 / C.E. Clarke Collection / AMNZ 40734 ; 1, Titirangi , Auck., 21-6-31, J. Bishop / AMNZ 40728 ; 3, Waitakere , 21-8-32, C.E. Clarke / C.E. Clarke Collection / AMNZ 40723 , 40724 , 40725 ( AMNZ) ; 1, NEW ZEALAND, AK, Waitakere Ra. , Cascade Kauri Park, Anderson Tr. 85m, 8.xii.84 – 25.i.85, hdwd-podocarp, A. Newton / M. Thayer 681 / window trap / G. Lovei Collection / AMNZ 50791 ; 1, 29.12.47, Waitakere Ras., C.T. / AMNZ 40732 ( AMNZ); 1 ♂ , NEW ZEALAND AK, Goldie Bush Sce. Res. , 100 m, 3650 S 17428 E, 27.XII.2005 / wet broadleaf-podocarp forest, walking in sunshine on track, 2 pm. Lead-smelling when seized ( NZAC) .

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 54. Mecodema spiniferum 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.