Mecodema oblongum Broun, 1882

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 : 81-83

Mecodema oblongum Broun, 1882 .

Figures 16A and 42 .

Metaglymma oblonga Broun, 1882 (The Brothers, SD), redescribed by Broun 1886.

Mecodema sulcatum Sharp, 1886 , new synonymy.

Metaglymma sulcatum Sharp, 1886 , redescribed by Broun 1893b.

Metaglymma modicum Broun, 1894 (Wellington, WN), synonymised by Britton 1949.

Metaglymma doulli Broun, 1905 (north Canterbury, NC), synonymised by Britton 1949.

Metaglymma ovicolle Broun, 1914 b (Otaraia, WA), synonymised by Britton 1949.

Metaglymma insulare Broun, 1921 (Stephen’s Is., SD), synonymised by Britton 1949.

Diagnosis: Distinguished from other North Island Mecodema species by: 1, the anterior area of clypeus with narrow grooves (may be indistinct), 1 setose puncture each side bearing 1 seta; 2, posterior lateral sinuation indistinctly carinate and strongly angled inward; 3, pronotum narrow and strongly deflected, overall shape ovate; 4, the setal distribution along the ventral edge of the left paramere ( Fig. 42 LP).

Description: Length 11–19.3 mm, pronotal width 4.2–5 mm, elytral width 5.3–6 mm. Colour of entire body dark reddish-brown to black (including legs).

Head: Narrow and convex ( Fig. 14D ). Vertex smooth; vertexal groove narrow and well-defined medially, always shallow laterally (may be absent); small supraorbital puncture bearing 2–3 setae; supraorbital grooves absent or indistinct; frons ( Fig. 9 ) without microsculpture (shallow depressions may be present near tentorial area); frontoclypeal suture narrow and defined, tentorial pits small; anterior area of clypeus with narrow grooves (may be indistinct), 1 setose puncture each side bearing 1 seta ( Fig. 42 ). Labrum rectangular, apical edge slightly emarginated with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes squared ( Fig. 12G ), median process narrow and long, upward angle absent, indentation notched ( Fig. 12D ); mentum setae present. Submentum sclerite constriction narrow with 2–3 evenly spaced setae each side. Stipes with 2 basal setae. Gula pits large, suture defined, gula flat and smooth. Gena with fine lines forming an isodiametric pattern across entire area.

Prothorax: Prothoracic carina narrow the entire length, smooth to slightly crenulated with 4–7 setae each side ( Fig. 42 ), extended to anterior angle; posterior lateral sinuation indistinctly carinate, distinctly angled inward; pronotum narrow and definitely deflected laterally, overall shape ovate; midline impressed, medial impressions absent, disc without microsculpture (very fine wrinkles laterally if present); pronotal foveae shallow and narrow; anterior edge and posterior edge inwardly curved. Prosternum ( Fig. 2 ) concave without microsculpture; proepisternum without microsculpture. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Narrow and greatly deflected; humerus anteriorly convergent ( Fig. 6A ); basal margin weakly curved and bevelled to base, interval 1 extended to basal margin; lateral carina narrow the entire length, extended to humeral angle; humerus with 1–2 setose punctures without carina ( Fig. 42 ); suture definitely impressed; striae with small, regularly distributed asetose punctures, all equally impressed with a slightly increased puncture size laterally ( Fig. 42 ); intervals 1–8 flat to weakly convex; interval 9 may be 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, setose punctures small.

Ventral surface: Mesepisternum with sparsely distributed, obsolescent punctures; metepisternum without microsculpture; setose punctures present on mesocoxa (2) and metacoxa (2). All abdominal ventrites ( Fig. 2 ) finely lineate laterally (sparse), some populations may be extensively lineate across ventrites; ventrites 3–5 with 1 setose puncture each side of midline; ventrite 6 with setae present: ♂ with 2–3 closely spaced setae medially, apical edge a blunt point; ♀ with 2–3 closely spaced setae each side of midline, apical edge a flattened curve; lateral foveae absent. Anterior metaventrite process a long, very bluntly rounded triangle with a very narrow to indistinct carina.

Male genitalia: Apical portion of penis lobe symmetrically rounded, apical curve slightly flattened, deflection to right of vertical axis absent (VV); ventral edge of shaft of penis lobe curve to right absent (VV), shaft of penis lobe equally broad ( Fig. 42 PL), overall length slightly curved ventrally (LV) ( Fig. 16A ). Structures of the endophallus ( Fig. 4 ): lateral form of the apex of the central spicule rounded; dorsal form of the apex of the central spicule short and narrow; setal (scales) coverage of the apical plate moderate (26–75%); size of left setose flange small; size of right setose flange large. Left paramere basal lobe articulated at right angle to aedeagus, narrowly rectangular (gradually narrowed from base to arm), very short slope to arm ( Fig. 42 LP); arm long and narrow; terminal lobe relatively narrow and short, apical tuft with a few medium length setae ( Fig. 42 LP), very sparsely distributed, short setae may be present along ventral edge of arm (some specimens with setae extended along apical ½ of ventral edge); ventral edge curved. Right paramere very narrowly rectangular, gradually narrowed at ½ length to terminal lobe, double row of long to medium-lengthed setae (not abundant), extended along apical ½ of ventral edge ( Fig. 42 RP).

Female genitalia: Basal gonocoxite 1 short and broad with a few rugose wrinkles on ventral surface, internal dorso-lateral carina with 1 seta, near base of gonocoxite 2. Gonocoxite 2 ( Fig. 5 ) long and narrowly triangular, edges and apical portion reflexed (scoop-like). Ramus short and broad, curved inward apically.

Comments: Mecodema oblongum is widespread along the eastern regions of New Zealand and is sister taxon to a new species from Te Mata Peak, Havelock North, Hawke’s Bay.

Distribution: New Zealand, North Island, Hawke’s Bay, Waiarapa, Wellington; South Island: Malborough Sounds, Kaikoura, North Canterbury, Nelson and Marlborough Sounds.

Holotype: ( Mecodema insulare ), BMNH male labelled. Type [round label with red border] / 4158. [hw] / New Zealand. [red underlined] Broun Coll. Brit. Mus. 1922-482 / Stephens Isd. 29-10-1916. [hw] / Mecodema insulare . ♂ [hw].

Paratypes: (see Seldon & Leschen 2011).

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 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 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 42. Mecodema oblongum 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.