Mecodema zonula, Seldon & Buckley, 2019

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 : 141-143

Mecodema zonula sp. n.

Figure 67 .

Diagnosis: Distinguished from other North Island Mecodema species due to: 1, vertexal groove defined by sparse punctures entire length and short grooves laterally; 2, all striae with doubled small asetose punctures (end on end) followed by larger gap, more strongly impressed in anterior region to basal margin and striae 6–9 ( Fig. 67 ); 3, setose punctures present on mesocoxae (2) and metacoxae (3).

Description: Length 16–18.5 mm, pronotal width 4–5 mm, elytral width 5–6 mm. Colour of entire body reddish-brown to matte black, coxae reddish-brown, legs black.

Head: Narrow and flat ( Fig. 14C ). Vertex with wrinkles, may also have a few short grooves; vertexal groove defined by sparse punctures the entire length and short grooves laterally ( Fig. 67 ); small supraorbital puncture bearing 2–4 setae; 2–3 shallow supraorbital grooves anterad eye; frons smooth; frontoclypeal suture poorly defined, tentorial pits small within a larger depression; anterior area of clypeus with indistinct microsculpture, latero-anterior edges of clypeus extended, 1 setose puncture each side bearing 1–3 setae ( Fig. 67 ). Labrum rectangular, anterior edge slightly emarginated with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded ( Fig. 12F ) and angled posterad, median process broad and short with a narrow carina, moderately angled upward (30°), moderately indentate ( Fig. 12B ); mentum setae present. Submentum sclerite ( Fig. 8 ) constriction broad with 6 evenly spaced setae, anterad punctures submentum has a strongly rolled fold. Stipes with 2 basal setae. Gula pits small in well-defined suture, gula slightly convex with very fine transverse lines. Gena with strong rugose wrinkles forming an isodiametric pattern.

Prothorax: Prothoracic carina narrow the entire length, moderately crenulated with 7–8 setae ( Fig. 67 ), extended beyond anterior angle; posterior lateral sinuation indistinctly carinate, inwardly angled; pronotum narrow and greatly deflected, overall shape ovate ( Fig. 67 ); midline impressed, anterior medial and posterior medial impressions absent, disc with very fine transverse lines laterally; pronotal foveae very shallow and narrow; anterior edge distinctly curved, posterior edge outwardly curved laterally, then inwardly curved medially. Prosternum ( Fig. 2 ) flat with very fine transverse lines and very sparsely micropunctate laterally; proepisternum extensively micropunctate across entire area. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Narrow and greatly deflected; humeral angle anteriorly convergent ( Fig. 6A ); basal margin sharply angled posterad from humerus, then curved anteriorly perpendicular to sharp angle (waist appears very distinctly narrowed) and gently sloped to base, interval 1 extended to scutellum; lateral carina very narrow in apical ¾, but broadened slightly in posterior ⅓ ( Fig. 67 ), extended to humeral angle; humerus with 1–3 setose punctures proximate the angle, 4 th double-spaced posterad ( Fig. 67 ); suture defined to poorly defined by flattened intervals; all striae with doubled small, asetose punctures (end on end) followed by larger gap, more distinctly impressed in anterior region to basal margin and striae 6–9; all intervals flat; interval microsculpture absent; 7 th strial setal pattern with 2–3 setose punctures in anterior ½, 3–4 setose punctures in posterior ½ ( Fig. 67 ), setose punctures large.

Ventral surface: Mesepisternum with numerous large pits; metepisternum sparsely pitted, extended onto ventrite 1; setose punctures present on mesocoxae (2) and metacoxae (3). All abdominal ventrites ( Fig. 2 ) lineate with some sparse obsolescent punctures; ventrites 3–5 with 1 setose puncture each side of midline; ventrite 6 setae present: (♂ no specimen available), ♀ with 1–2 setae each side of mid line; ventrites foveate (very shallow depressions) laterally. Anterior metaventrite process a short triangle with a broad carina the entire length.

Male genitalia: no male specimen available.

Female genitalia: Basal gonocoxite 1 long and narrow, ventral surface smooth, internal dorso-lateral carina without setae. Gonocoxite 2 ( Fig. 5 ) triangular and flat, ventral surface covered in sensillae, dorsal surface concave. Ramus long and broad at base, narrowing to apex.

Comments: Specimens of Mecodema zonula (Mt Hector only) were found in the New Zealand Arthropod Collection amongst specimens of the more widely distributed M. dux , which is found in the Tararua and Ruahine Ranges. However, Mecodema zonula is found on the lower slopes to approximately 1370 m of Mt Hector, Tararua Ranges.

Distribution: New Zealand, North Island, Tararua Range, Mt Hector.

Holotype: NZAC female labelled. E87 HECTOR TRACK TARARUA RA, R.M. BULL 13.3.61 [hw] / R.M. Bull Collection / N.Z. Arthropod Collection NZAC Entomology Div. DSIR Auckland NEW ZEALAND [gold label] / HOLOTYPE Mecodema zonula n. sp. design. DS Seldon, TR Buckley 2018 [red label].

Paratypes: 1♀, E29 LOWER HECTOR TRACK R.M. BULL 29.11.58 [hw] / R.M. Bull Collection / N.Z. Arthropod Collection NZAC Entomology Div. DSIR Auckland NEW ZEALAND [gold label]; 1♀, E92 HECTOR TRACK R.M. BULL 12.2.62 [hw] / R.M. Bull Collection / N.Z. Arthropod Collection NZAC Entomology Div. DSIR Auckland NEW ZEALAND [gold label] / NZAC04005121 ; 1♀, MT HECTOR 4500 ’ R.M. BULL 14.12.63 [hw] / R.M. Bull Collection / N.Z. Arthropod Collection NZAC Entomology Div. DSIR Auckland NEW ZEALAND [gold label] .

Etymology: Zonula is Latin for small belt. In this species M. zonula , the angle of the humerus and the opposing angle of the basal margin form a distinctively narrowed waist with a belt-like appearance between the pronotum and elytra.

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 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 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 67. Mecodema zonula (female specimens only) plate with half habitus (left). The bottom scale bar is the width across the widest point of the pronotum of the specimen used for this habitus.