Mecodema chaiup Seldon, 2015

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 : 34-36

Mecodema chaiup Seldon, 2015 .

Figure 22 .

Diagnosis: Distinguished from other North Island Mecodema by: 1, the narrow elytra (narrower than the pronotum at the widest point); 2, the distinct asetose punctures in a confused pattern that are irregular in size and shape ( Fig. 22 ).

Description: Length 31 mm, pronotal width 8.5 mm, elytral width 6.5 mm. Colour of entire body matte black, except femur and tibiae are dark reddish-brown.

Head: Broad and flat ( Fig. 14A ). Vertex ( Fig. 9 ) with very fine lines forming an isodiametric pattern; vertexal groove defined by enlarged frons, groove broadened laterally; small supraorbital puncture bearing 4–5 setae; 4 shallow supraorbital grooves anterad eyes; large cuticular depressions latero-posterad eye and supraorbital puncture; frons with small circular depressions laterally within a larger frontal depression; frontoclypeal suture narrow and defined with tentorial pits indistinct within a larger depression; anterior area of clypeus with 3 narrow grooves, central groove with setose puncture bearing 1 seta, 1 setose puncture each side bearing 3 setae. Labrum lobate, anterior edge moderately emarginated with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded ( Fig. 12F ), median process very broad and long, apex distinctly angled upward (60°), distinctly indentate ( Fig. 12A ); mentum setae absent. Submentum sclerite ( Fig. 8 ) constriction broad with 6 setae, with a broad gap medially. Stipes with 3 basal setae. Gula pits narrow and deep, suture well-defined, gula flat with very fine transverse wrinkles. Gena with wrinkled isodiametric pattern across the entire area.

Prothorax: Prothoracic carina broad the entire length, slightly crenulated in anterior portion with 8–12 setae each side, extended beyond humeral angle; posterior lateral sinuation indistinctly carinate, parallel; pronotal lateral margin broad in anterior half, disc flattened anteriorly, anterior lateral margin of pronotum angled sharply posterad ( Fig. 22 ), overall shape cordate; midline well-defined, anterior medial and posterior medial diamond-shaped impressions present, disc with transverse lines across entire area; pronotal foveae ( Fig. 11 ) very broad and shallow; anterior edge slightly inwardly curved, posterior edge strongly curved each side, inwardly curved medially. Prosternum concave with light transverse wrinkles present; proepisternum ( Fig. 2 ) sparsely micropunctate. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Broad and flattened but narrower than pronotum (at broadest point), posterior end of elytra steep to apex; humeral angle evenly convex ( Fig. 6B ); basal margin slightly curved and gently sloped to base, interval 1 extended to scutellum; lateral carina narrow the entire length, extended to humeral angle; humerus with 3–4 setose punctures proximate the angle then 1 spaced equally between umbilical series ( Fig. 22 ); suture well-defined with sutural intervals clearly defined and microsculpture absent; intervals 2–6 indistinct but contributing to confused pattern of striae; asetose punctures very irregular in size and shape; 7 th strial ( Fig. 1 ) setal pattern with 4 setose punctures in anterior ½, 3 setose punctures in posterior ½ to apex, setose punctures large.

Ventral surface: Mesepisternum micropunctate; metepisternum without microsculpture; setose punctures present on mesocoxae (2) and metacoxae (2). Abdominal ventrites 1–5 ( Fig. 2 ) finely lineate, ventrites 1 and 2 micropunctate; ventrites 3–5 with 1 setose puncture each side of midline; lateral foveae absent; ventrite 6 setae present: ♂ with 1 seta each side distantly spaced at opposite ends of straight apical edge and junction of curve anterad (no ♀ specimen available). Anterior metaventrite process ( Fig. 2 ) triangular with a well-defined and broad carina the entire length.

Male genitalia: Apical portion of penis lobe asymmetrically hooked, without deflection to right (VV); dorsal process rounded and apically flattened i.e., hammer-like in shape, ventral process shorter and more rounded ( Fig. 22 PL), pushed forward so not perpendicular to shaft ( Fig. 3 ); penis lobe shaft equally narrow the entire length, ventral edge distinctly curved to right (VV), overall length of the penis lobe distinctly curved ventrally (LV) ( Fig. 16C ). Structures of the endophallus ( Fig. 4 ): lateral form of the apex of the central spicule flattened; dorsal form of the apex of the central spicule greatly expanded with a projection; setal (scales) coverage of the apical plate moderate (26–75%); left setose flange small; right setose flange absent. Left paramere basal lobe rectangular, broadened and humped dorsally forming a steep anterior angle (60°) to arm ( Fig. 22 LP), ventral edge very straight; arm angled downward, ventral edge curved upward to form short narrow arm; terminal lobe rounded, broader than arm with a long tuft of setae at apex; setae extended along apical ½ of ventral edge, very sparse on arm. Right paramere long, narrow and triangular with apical ⅓ curved inwardly toward penis lobe, numerous long setae extended along apical ½ of ventral edge ( Fig. 22 RP).

Female genitalia: no female specimen available.

Comments. The only specimen of this species was collected in Mohi Bush Scenic Reserve, Maraetotara Plateau in January 2008. Since then there has been a number of extensive, but unsuccessful pitfall trapping events to collect further specimens.

Distribution. New Zealand, North Island, Hawke’s Bay, Maraetotara Plateau, Mohi Bush Scenic Reserve.

Holotype. NZAC male labelled. NEW ZEALAND, HB, Mohi Bush Scenic Reserve , 2 January 2008, ♂ D.S. Seldon & C.P. Martin, S39°51 24.5" E176°53 56.2" / HOLOTYPE Mecodema chaiup sp. nov. Design. by D.S. Seldon 2014 [red label] / NZAC04095692 (see Seldon 2015) .

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 3. Detail of the apical portion of aedeagus (male genitalia) with parameres removed showing taxonomic structures, vertical and horizontal planes that are referred to in the species descriptions and redescriptions: aedeagus shaft width (ASW); vertical central line (ƑCL) [dashed line, not a structure]; horizontal central line (HCL) [dashed line, not a 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 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 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 22. Mecodema chaiup 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.