Mecodema oconnori Broun, 1912

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 : 83-85

Mecodema oconnori Broun, 1912 .

Figures 6B and 43 .

Diagnosis: Differs from other North Island Mecodema species by: 1, its large and robust body size; 2, elytral intervals 8 and 9 terminating short of basal margin; 3, apical shape of the penis lobe ( Fig. 43 PL); 4, the setal distribution along the ventral edge of the left paramere ( Fig. 43 LP).

Description: Length 29–34 mm, pronotal width 7.9–10.4 mm, elytral width 9.3–11.7 mm. Colour of head and pronotum glossy black, elytra matte black, ventral surface dark reddish-brown to black, including legs (may be a darker red).

Head: Very broad and flat. Vertex with fine to rugose wrinkles forming an isodiametric pattern laterally; vertexal groove ( Fig. 9 ) well-defined the entire length, narrow medially and broadened laterally, punctures and rugose wrinkles present variably laterally or medially ( Fig. 43 ); large supraorbital puncture bearing 4–6 setae; 2–4 indistinct to distinct supraorbital grooves (some specimens without grooves); frons medially convex with a large depression each side, may be micropunctate anterad; frontoclypeal suture indistinct, tentorial pits small; anterior area of clypeus ( Fig. 9 ) with well-defined grooves, 1 setose puncture each side bearing 2 setae (central puncture bearing 2 setae found in northern specimens e.g., Pohangina Valley). Labrum rectangular, anterior edge slightly emarginated or emargination may be absent with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded ( Fig. 12F ), median process broad and short, slightly angled upward (15°), moderately indentate ( Fig. 12B ); mentum setae variably absent or present. Submentum sclerite constriction narrow with 6–8 evenly distributed setae. Stipes with 2 basal setae. Gula pits ( Fig. 8 ) small, suture indistinct to defined, gula flat with tranverse lines. Gena with rugose wrinkles forming an isodiametric pattern across entire area.

Prothorax: Prothoracic carina broad the entire length, slightly crenulated with 8–13 setae ( Fig. 43 ), extended beyond anterior angle; posterior lateral sinuation evidently carinate, parallel; pronotum broad and flat, slightly deflected laterally, overall shape cordate ( Fig. 43 ); midline impressed, anterior medial and posterior medial diamond-shaped impression present, disc with fine transverse wrinkles, some specimens with a small depression laterally anterad foveae; pronotal foveae broad and shallow; anterior edge strongly inwardly curved, posterior edge straight (may be slightly emarginated). Prosternum ( Fig. 2 ) flat with fine transverse wrinkles; proepisternum with wrinkles, some obsolescent punctures may be present. 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 medially but broadened in anterior ⅓ and posterior ⅓, extended beyond humeral angle; humerus with 3–4 setose punctures in angle ( Fig. 43 ); suture poorly impressed; striae with small, regularly spaced asetose punctures; striae 1– 4 may have obsolescent punctures in some specimens; intervals 1–4 weakly convex, intervals 5–8 moderately convex, intervals 8 and 9 terminate short of basal margin; interval microsculpture present as fine wrinkles; 7 th strial setal pattern ( Fig. 1 ) with 3–4 setose punctures in anterior ½, 5–6 setose punctures in posterior ½, setose punctures small.

Ventral surface: Mesepisternum with a few punctures and pitting (rugose wrinkles may be present); metepisternum ( Fig. 2 ) with very sparse punctures and rugose wrinkles; setose punctures present on mesocoxa (1–2) and metacoxa (2–3). All abdominal ventrites lineate, ventrites 1 and 2 may have pitting present laterally; ventrites 3–5 with 1 setose puncture each side of midline; 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, 1 proximate medially, other at junction of the straight apical edge and curve anterad; lateral foveae absent. Anterior metaventrite process ( Fig. 2 ) a short bluntly rounded triangle with a broad and well-defined carina.

Male genitalia: Apical portion of penis lobe asymmetrically hooked with a distinct deflection to right of vertical axis (VV) ( Fig. 15A ); a short ventral process with a rounded point pushed forward of central vertical axis ( Fig. 3 ), apex flatly curved upward to form a short and broad dorsal process ( Fig. 43 PL) with a very flat hook (posterad central vertical axis), a short and sharp recurve to shaft (LV) (overall breadth of apical portion may vary in some specimens); shaft of penis lobe narrow but gradually broadened to base, shaft ventral edge curve to right absent (VV); 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 extensive (76–100%); size of left setose flange small; size of right setose flange absent. Left paramere basal lobe a short rectangle with small dorsal hump, very steep slope (60°) to arm ( Fig. 43 LP); arm long and narrow; terminal lobe short and broad with a tuft long apical setae, apical lobe and arm setae absent along; very sparsely distributed medium-lengthed setae from arm junction extended to apical ½ of basal lobe ventral edge ( Fig. 43 LP); ventral edge straight. Right paramere long, rectangular and narrowed to apex, terminal lobe with a dense tuft of long setae, double row of medium setae extended along apical ¾ of ventral edge ( Fig. 43 RP).

Female genitalia: Basal gonocoxite 1 short and broad, apically flattened, ventral surface entirely covered with well-defined rugose wrinkles; internal dorso-lateral carina with 3 short setae. Gonocoxite 2 ( Fig. 5 ) long, relatively narrow, rounded, triangular and apically reflexed. Ramus very long and narrow.

Comments: Townsend (2012) proposed that M. oconnori is widespread throughout the North Island, especially the Central Plateau, extending northward into the Waikato, and eastward into the Hawke’s Bay. However, larger native forest fragments often have a resident oconnori -like species that shares its habitat sympatrically with one or more Mecodema species, e.g. M. crenaticolle and/or M. curvidens .

Distribution: New Zealand, North Island, north and south of the Manawatu River, Levin, Dannevirke, Taihape.

Holotype: BMNH specimen labelled. Type [round label with red border] / 3164 [hw] / New Zeal. [red underline] Broun Coll. Brit. Mus. 1923-482 / Levin Wellington [hw] / Mecodema oconnori [hw].

Material examined: 1♂, Levin 1/12/56 J.T. [hw] / Mecodema O’connori Det. J.I. Townsend [hw] ( NZAC) ; 1 ♂, NEW ZEALAND WN, Lake Papaitonga Sc Res , Levin, 22 Oct 1999 M Hutchison Pit fall traps ; 1♀, NEW ZEALAND WN Lake Papaitonga Sc Res Levin , 28 Jan 2000 M Hutchison Pit fall traps ( NZAC) ; 1♂, Levin WN under log 4.1.1991 C.A. Stewart [hw] / LUNZ00002706 ; 1, NEW ZEALAND, WI, Bruce Park , SH1 260m, 3–6 ii 2000, J.W. Early, Rimu /tawa forest. Yellow pan trap. L7572 / AMNZ 27702 [green label]; 1, Johnson Park , Fielding Nov / Dec 1961 R. Rowe [hw] / R. Rowe Collection / AMNZ 40841 [green label]; 1♀, 1♂, NEW ZEALAND RI, Taihape , Paengaroa S.R. 24 Dec 2017, M.R. Dickison / under logs by hand, podocarp-broadleaf forest, S39°38’49” E175°43’33” 510 m ( WMNZ) .

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 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 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 43. Mecodema oconnori 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.