Mecodema simplex Castelnau, 1867

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 : 107-109

Mecodema simplex Castelnau, 1867

Figure 53 .

Mecodema acuductum Broun, 1908 (Mt Holdsworth, WN), synonymised by Britton 1949.

Mecodema bryodium Broun, 1912 (Silverstream, WN), synonymised by Britton 1949.

Mecodema arcuatum Broun, 1912 (near Martinborough, WA), synonymised by Britton 1949.

Diagnosis: Differing from other North Island Mecodema species by having: 1, numerous punctures along vertexal groove and vertex; 2, pronotum carina with 5 setae along each side; 3, elytra with star-shaped punctures, punctures equal size entire; 4, distinctive shape of the apical portion of the penis lobe ( Fig. 53 PL).

Description: Length 22.6–30 mm, pronotal width 6.4–8 mm, elytral width 7.3–9.9 mm. Colour of entire body matte to glossy black, except the elytra, ventral surface and legs dark reddish-brown.

Head: Broad and convex ( Fig. 14B ). Vertex with numerous punctures and rugose wrinkles laterally; vertexal groove broad and shallow, defined by punctures the entire length ( Fig. 53 ); small supraorbital puncture within larger groove bearing 3–4 setae; 4–5 well-defined supraorbital grooves extended onto frons; frons medially convex with a broad and deep depression each side, transverse grooves present; frontoclypeal suture and tentorial pits indistinct; anterior area of clypeus ( Fig. 9 ) with broad and shallow grooves laterally, medial grooves narrow; 1 setose puncture each side bearing 1–2 setae ( Fig. 53 ). Labrum lobate, anterior edge outwardly curved, moderately 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 (45°), moderately indentate ( Fig. 12B ); mentum setae absent. Submentum sclerite ( Fig. 8 ) constriction narrow with 3 setae laterally (with a large gap medially). Stipes with 2 basal setae. Gula pits small, suture well-defined the entire length, gula slightly convex with transverse lines. Gena ( Fig. 8 ) with rugose wrinkles forming an isodiametric pattern laterally.

Prothorax: Prothoracic carina ( Fig. 11 ) broad the entire length, moderately crenulated with 5 setae each side, extended beyond anterior angle; posterior lateral sinuation evidently carinate, parallel; pronotum broad and deflected laterally, overall shape cordate (pronotal edge right angled apically); midline well-defined, anterior medial and posterior medial diamond-shaped impressions present, disc with fine transverse lines turning to welldefined wrinkles laterally ( Fig. 53 ), may have obsolescent punctures mesad foveae; pronotal foveae broad and deep; anterior edge slightly inwardly curved, posterior edge straight, medially emarginated. Prosternum slightly convex and smooth; proepisternum densely pitted. Procoxal setae absent; protibia distally expanded and shovellike ( Fig. 10B ).

Elytra: Broad and deflected laterally; humeral angle anteriorly convergent ( Fig. 6A ); basal margin slightly curved and gently sloped to base, interval 1 extended to scutellum; lateral carina narrow the entire length, broadened apically, extended to humeral angle; humerus with 3 setose punctures closely spaced, 4 th double-spaced posterad; suture well-defined; striae with regularly sized and spaced, asetose punctures striae 1–4 extended beyond basal margin; intervals 3, 5 and 7 moderately convex, interval 9 strongly convex, especially anterior ⅓; interval microsculpture in form of fine lines radiating outwardly from punctures (star-shaped); 7 th strial setal pattern with 3 setose punctures in anterior ½, 4 setose punctures in posterior ½ ( Fig. 53 ), setose punctures small.

Ventral surface: Mesepisternum and metepisternum ( Fig. 2 ) with numerous punctures across entire area and spilling onto latero-posterior edges of mesosternum; setose punctures present on mesocoxa (2) and metacoxa (2). All abdominal ventrites lineate, ventrite 1 sparsely micropunctate; ventrites 3–5 with 1 setose puncture each side of midline; ventrite 6 setae present: ♂ with a single setose puncture each side near junction of straight apical edge and curve anterad; ♀ with 2 setose punctures each side, apical edge straight between first pair; ventrites 3–6 foveate laterally. Anterior metaventrite process ( Fig. 2 ) a short and sharp triangle with a very broad and pronounced carina the entire length.

Male genitalia: Apical portion of penis lobe asymmetrically hooked (almost symmetrical) with a slight deflection to right of vertical axis (VV) ( Fig. 15C ); ventral process curved from shaft to form a rounded point at centre of vertical axis, apex is broadly and symmetrically curved upwards to form dorsal process ( Fig. 53 PL) with a more rounded point (behind ventral point) that recurves to shaft, both relatively the same depth (LV); shaft of penis lobe narrow but gradually broadened toward base ( Fig. 53 PL); ventral edge of penis lobe shaft with moderate curve to left, basal to apical portion curve to right (VV); overall length of penis lobe with dictinct curve 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 extensive (76–100%); size of left setose flange small; size of right setose flange large. Left paramere articulated at right angle from penis lobe, basal lobe rectangular with large dorsal hump (almost making lobe triangular) that forms steeply (60°) curved slope to arm ( Fig. 53 LP); arm short and narrow; terminal lobe short and broad with apical tuft of long setae, short setae extended along edge, longer comb prior to arm junction; setae extended along apical ½ of straight ventral edge ( Fig. 53 LP). Right paramere narrowly triangular with a double row of long to medium-lengthed setae extended along apical ¾ of ventral edge ( Fig. 53 RP), curved inwardly apically.

Female genitalia: Basal gonocoxite 1 short and narrow, apically broadened, ventral surface smooth, internal dorso-lateral carina ( Fig. 5 ) with 2 setae. Gonocoxite 2 bluntly rounded triangle, slightly reflexed apically. Ramus ( Fig. 5 ) short and broad.

Comments: The holotype locality is Auckland, but we suggest that this refers to the Auckland Province that in the 1860s extended from Cape Reinga to the 39 th latitude. This southern boundary would be the most northern range of Mecodema simplex , which is much more prevalent in the Wairarapa region.

Distribution: New Zealand, North Island, eastern Tararua Ranges, Hawke’s Bay, Rangitikei, Wairarapa, Wellington.

Holotype: MCNG specimen labelled. Auckland Coll. Castelnau [hw, black border] / Typus [red font, red border] / simplex Cast. [hw] / Simplex Cast . / HOLOTYPUS Mecodema simplex Castelnau 1867 [hw, red label] / Museo Civico di Genova .

Paratypes ( Mecodema simplex ): BMNH card-mounted male labelled. Type [round label with red border glued to card] / 2602 ♂ [hw] / New Zeal. [red underline] Broun Coll. Brit. Mus. 1922-482 / Mt. Holdsworth Tararua [hw] / Mecodema acuductum [hw]. BMNH male labelled. Type [round label with red border] / 3115 [hw] / New Zeal. [red underline] Broun Coll. Brit. Mus. 1922-482 / Silverstream Wellington [hw] / Mecodema bryobium ♂ [hw] / card-mounted male genitalia; BMNH female labelled. Type [round label with red border] / 3168 [hw] / New Zeal. [red underline] Broun Coll. Brit. Mus. 1922-482 / Martinboro Wellington [hw] / Mecodema arcuatum ♀ [hw].

Material examined: 1♂, Manawatu Gorge , Bellance Reserve, RI /WN, forest pitfall 3/2, 23/2/92 coll. G. Lovei / G. LOVEI COLLECTION / AMNZ 503340 [green label]; 1♀, NEW ZEALAND WA Puketoi SF J. Nunn 2411 11 Apr 76 [hw] / Mecodema simplex det. J. Nunn [hw] ( JNPC) .

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 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 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 53. Mecodema simplex 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.