Mecodema yconomus, 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 : 138-140

Mecodema yconomus sp. n.

Figure 66 .

Diagnosis: Differing from the other North Island Mecodema species due to: 1, large supraorbital puncture bearing 5–6 setae; 2, 7 th elytral strial setal pattern with 3–4 setose punctures in anterior ½, 5–7 setose punctures in posterior ½, setose punctures large; 3, distinct shape of the apical portion of the penis lobe ( Fig. 66 PL).

Description: Length 28–36.5 mm, pronotal width 7.5–10.4 mm, elytral width 8.6–11.6 mm. Colour of body dorsally matte black, ventrally dark reddish-brown to black, trochanter and femur reddish-brown, legs black.

Head: Very broad and flat. Vertex with very fine lines forming an isodiametric pattern laterally; vertexal groove shallow and narrow, defined by punctures ( Fig. 66 ) and short grooves; large supraorbital puncture bearing 5–6 setae; 2–3 shallow supraorbital grooves; frons with a large and shallow depression each side of midline (may have grooves laterally); frontoclypeal suture narrowly defined (may be indistinct), tentorial pits ( Fig. 9 ) small, area between pits medially convex; anterior area of clypeus with narrow and deeply impressed grooves laterally, broader and shallower grooves medially, 1 small setose puncture each side bearing 2 setae ( Fig. 66 ). Labrum rounded, anterior edge curved with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded ( Fig. 12F ), median process very short and broad, moderately angled upward (30°), strongly indentate ( Fig. 12A ); mentum setae absent. Submentum sclerite constriction broad with 6 evenly distributed setae. Stipes with 2 basal setae. Gula pits ( Fig. 8 ) large, suture poorly defined, gula slightly convex with fine transverse lines. Gena with fine wrinkles across entire area.

Prothorax: Prothoracic carina broad the entire length, slightly crenulated with 8–12 setae, extended beyond anterior angle; posterior lateral sinuation evidently carinate, parallel; pronotum broad, moderately deflected laterally, overall shape broadly cordate ( Fig. 66 ); midline well-defined, very deeply impressed anterior medial triangular impression and posterior medial diamond-shaped impression present, disc with very fine transverse wrinkles laterally ( Fig. 66 ); pronotal foveae ( Fig. 11 ) very broad and shallow; anterior edge slightly inwardly curved, posterior edge relatively straight (slightly emarginated medially). Prosternum flat and smooth; proepisternum without microsculpture. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Broad and strongly deflected; humeral angle evenly convex ( Fig. 6B ); basal margin moderately curved and gently sloped to base, interval 1 ( Fig. 1 ) extended to scutellum; lateral carina narrowed medial ⅓, but broadened in anterior and posterior ⅓, extended beyond humeral angle; humerus with 4–5 setose punctures, 3 or 4 proximate, 1–2 double-spaced posterad ( Fig. 66 ); suture poorly impressed; striae with small, regularly spaced, asetose punctures, striae 1–5 with obsolescent punctures, increased defined laterally; intervals 1–4 weakly convex, intervals 5–9 moderately convex; interval microsculpture present as fine transverse lines; 7 th strial setal pattern with 3–4 setose punctures in anterior ½, 5–7 setose punctures in posterior ½ ( Fig. 66 ), setose punctures large.

Ventral surface: Mesepisternum and metepisternum with wrinkles and obsolescent punctures; setose punctures present on mesocoxa (2) and metacoxa (2). All abdominal ventrites ( Fig. 2 ) lineate; ventrites 3–5 with 1 setose puncture each side of midline; ventrite 6 setae present: ♂ with 1 setose puncture proximate junction of straight apical edge and curve anterad, ♀ with 1–2 setose punctures along bluntly rounded apical edge; lateral foveae absent. Anterior metaventrite process ( Fig. 2 ) a narrow triangle with a narrow carina the entire length.

Male genitalia: Apical portion of penis lobe asymmetrically hooked with a distinct deflection to right of vertical axis (VV) ( Fig. 15A ), penis lobe shaft curves slightly to left due to deflection (VV); shaft of penis lobe narrow the entire length, overall length of penis lobe slightly curved ventrally (LV) ( Fig. 16A ); apical ventral edge of shaft curves downward to form a bluntly rounded, long and narrow ventral process that is angled forward of vertical axis, apex flatly curved upward ( Fig. 66 PL), extended to form short and flatly curved dorsal process, a brief, almost straight angle to shaft ( Fig. 66 PL). 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 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 shorter in length and only slightly broader than right paramere ( Fig. 66 LP), ovate with dorsal hump forming a moderate (45°) slope to arm; arm short and broad (part of continuous slope); terminal lobe short and narrow with apical tuft of medium-lengthed setae, short setae along ventral edge to longlengthed setal comb along arm ( Fig. 66 LP); setae extended along apical ½ of curved ventral edge. Right paramere narrowly rectangular, gradually narrowed to terminus with a double row of long setae extended along apical ½ of ventral edge ( Fig. 66 RP), apical portion slightly inwardly curved toward penis lobe.

Female genitalia: Basal gonocoxite 1 short and broad, ventral surface with a few rugose wrinkles, internal dorso-lateral carina ( Fig. 5 ) with 3 setae. Gonocoxite 2 long and narrow, almost flattened. Ramus long and narrow.

Comments: Mecodema yconomus is a relatively large ground beetle that inhabits the eastern areas of podocarp-broadleaf forest amongst the hills of the Maungaharuru Range. Even though it appears to share some of its range sympatrically with M. validum , both species are separated by altitude, with M. validum usually found above 700 m a.s.l. and M. yconomus found below 500 m a.s.l.

Distribution: New Zealand, North Island, Hawkes Bay, eastern and southern Maungaharuru Range, Te Waka and Maniaroa Ranges, Boundary Stream Mainland Island, William Hartree S.R.

Holotype: NZAC male labelled. NEW ZEALAND HB, Boundary Stream Mainland Island BSMI 6.5 , Dec 1998 – Jan 1999, DoC PTs / HOLOTYPE Mecodema yconomus n. sp. design. DS Seldon, TR Buckley 2018 [red label].

Paratypes: 11, NEW ZEALAND HB, Tutira , Thomas Bush PTs, 15 Dec 2010 – 15 Jan 2011, DoC, M. Melville ( NZAC) ; 2, NEW ZEALAND HB, Tutira , Thomas Bush PTs, 15 Dec 2010 – 15 Jan 2011, DoC, M. Melville ( MONZ) ; 2, NEW ZEALAND HB, Tutira , Thomas Bush PTs 6.3, 15 Dec 2010 – 15 Jan 2011, DoC, M. Melville ( AMNZ) ; 2, NEW ZEALAND HB, Tutira , Thomas Bush PTs, 15 Dec 2010 – 15 Jan 2011, DoC, M. Melville ( LUNZ) ; 2, NEW ZEALAND HB, Tutira , Thomas Bush PTs, 15 Dec 2010 – 15 Jan 2011, DoC, M. Melville ( CMNZ) .

Etymology: This species is relatively abundant on the lower altitudinal forest and therefore, a guardian of Boundary Stream Mainland Island. Yconomus means guardian.

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 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 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 66. Mecodema yconomus 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.