Mecodema aberrans Putzeys, 1868

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 : 17-22

Mecodema aberrans Putzeys, 1868 , comb. n.

Figure 13 .

Metaglymma aberrans Putzeys, 1868b .

Metaglymma tersatum Broun, 1893a (Lake Tekapo, MK), synonymised by Britton (1949).

Metaglymma thoracicum Broun, 1893a (Moeraki, DN), synonymised by Britton (1949).

Metaglymma rugiceps Broun, 1903 (Albury, SC), synonymised by Britton (1949).

Diagnosis: Distinguished from other Mecodema species by having: 1, ventrites 3–5 bearing numerous setose punctures; 2, elytral stria 9 with asetose punctures that are 2x the size of the punctures of elytral stria 1; 3, shape of the basal lobe and the setal distribution along the ventral edge of the left paramere ( Fig. 13 LP).

Description: Length 14.6–19.5 mm, pronotal width 4.6–5.7 mm, elytral width 5.3–6.5 mm. Colour dorsally matte to glossy black, ventrally matte to glossy dark brown to black, legs may be reddish-brown.

Head: Broad and convex ( Fig. 14B ).Vertex smooth; vertexal groove broad and shallow laterally, absent medially; large supraorbital puncture bearing 3 setae; 1 poorly defined supraorbital groove; frons with a small and shallow depression each side of midline (anteriorly); frontoclypeal suture a narrow straight groove between small defined tentorial pits; anterior area of clypeus smooth, 1 deep setose puncture each side bearing 1 seta. Labrum laterally rounded, anterior edge straight with 3 evenly spaced setae along each side. Mentum lobes squared ( Fig. 12G ), mentum process long and narrow, slightly angled upward (15°), moderately indentate ( Fig. 12B ); mentum setae variably present or absent. Submentum sclerite constriction narrow with 6 setae. Stipes with 2 basal setae. Gula pits large and deep, suture well-defined, gula flat and smooth. Gena ( Fig. 8 ) with fine wrinkles forming an isodiametric pattern across entire area.

Prothorax: Prothoracic carina broad the entire length, slightly crenulated with 7–8 setae each side ( Fig. 13 ), extended to anterior angle; posterior lateral sinuation indistinctly carinate, angled inward; pronotum broad and moderately deflected laterally, overall shape cordate; midline ( Fig. 11 ) indistinct, anterior medial impression absent, posterior medial diamond-shaped impression present, disc smooth (may have a few very fine lines laterally); pronotal foveae broad and deep; anterior edge inwardly curved, posterior edge straight. Prosternum concave with very fine transverse lines; proepisternum without microsculpture. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Broad and distinctly deflected laterally, length truncated with steep slope to elytra apex; form of humeral angle evenly convex ( Fig. 6B ); basal margin slightly curved and bevelled to base, interval 1 extended to margin; lateral carina ( Fig.1 ) narrow in apical ⅓ and medial ⅓, broad in posterior ⅓, extended to humeral angle; humerus with 3–4 setose punctures; suture well-defined; striae consisting of regularly spaced, asetose punctures, punctures increased in size laterally, stria 9 punctures 2x the size of stria 1 punctures; all intervals 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. 13 ), setose punctures large.

Ventral surface: Mesepisternum with rugose wrinkles; metepisternum with sparsely scattered obsolescent punctures; setose punctures present on mesocoxae (2–3) and metacoxae (2–3). All abdominal ventrites finely lineate laterally; ventrite 3 with 1–2 setose punctures each side (not laterally), ventrite 4 with 4–6 setose punctures each side of midline, ventrite 5 with 5–8 setose punctures each side of midline; ventrite 6 setae present: ♂ with 2 setose punctures each side along a blunt rounded apical edge, (♀ specimen not available); ventrites laterally foveate. Anterior metaventrite process a sharply pointed triangle with an indistinct carina the entire length.

Male genitalia: Apical portion of penis lobe symmetrically rounded ( Fig. 13 PL) with a slight deflection to right of vertical axis (VV) ( Fig. 15C ), apical curve flattened; shaft of penis lobe broad and straight (VV), overall length of penis lobe without straight (LV) ( Fig. 16A ). Structures of the endophallus ( Fig. 4 ): lateral form of apex of the central spicule rounded; dorsal form of apex of the central spicule narrow and short; setal (scales) coverage of the apical plate is sparse (1–25%); left setose flange is small, right setose flange is large. Left paramere basal lobe narrow and ovate with a short anterior slope to arm; arm very long (½ total length) and very narrow; terminal lobe indistinct from arm with an apical tuft of a few short setae; very sparse setae extended along apical ¾ length of ventral edge ( Fig. 13 LP), setae long on basal lobe; ventral edge curved. Right paramere of a very narrow triangularshape, gradually narrowed to apex, sparse setae along apical ¾ length of ventral edge ( Fig. 13 RP).

Female genitalia: no female specimen available.

Comments: One of the three species that are found in habitats along braided river systems to the coast of the Canterbury and Otago regions in the South Island.

Distribution: New Zealand, South Island, Dunedin (DN), Mid-Canterbury (MC), South Canterbury (SC) and Mackenzie (MK).

Holotype: not viewed. Type in the Natural History Museum, Brussels ( Britton, 1949).

Material examined: 1♂, NEW ZEALAND CO, Lake Waitaki, J. Nunn 4719, 2 NOV 83 [hw] / Metaglymma sp. [hw] / J.I. Townsend Collection; 1♂, NEW ZEALAND MC, Lyttelton, J. Nunn1412, 4 JAN 73 [hw] / Metaglymma sp. [hw] / J.I. Townsend Collection / NZAC04008021; 1, OAMARU 4.2.64 C.B. BULL [hw] / R.M. Bull Collection / NZAC04004599; 1, NEW ZEALAND CO, Lake Waitaki, J. Nunn 4719, 2 NOV 83 [hw] / Metaglymma sp. [hw] / J.I. Townsend Collection; 1, NEW ZEALAND CO, Lake Waitaki, J. Nunn 4816, 19 DEC 83 [hw] / J.I. Townsend Collection.

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 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 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 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 13. Mecodema aberrans 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.

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.