Mecodema scitulum Broun, 1894

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 : 104-106

Mecodema scitulum Broun, 1894 , revised status.

Figure 52 .

Diagnosis: Distinguishable from other North Island Mecodema species due to the: 1, vertexal groove defined by obsolescent punctures along the entire length; 2, elytral humerus with 3 setose punctures close to angle, 4 th puncture double-spaced (or more) posterad; 3, elytral intervals 1–6 flat, intervals 7 and 8 moderately convex, interval 9 strongly convex; 4, shape of the apical portion of the penis lobe ( Fig 52 PL).

Description: Length 22–26.5 mm, pronotal width 4.5–5.5, elytral width 6–7 mm. Colour of entire body matte black.

Head: Broad and flat ( Fig. 14A ). Vertex with fine, transverse wrinkles forming an isodiametric pattern laterally; vertexal groove broad medially and narrowed laterally, well-defined by obsolescent punctures the entire length ( Fig. 52 ); small supraorbital puncture bearing 3–4 setae; 4–6 narrow supraorbital grooves that extend onto frons, curving along anterior area of frons; frons medially convex (extended from frons to clypeus) with a small and shallow depression each side of midline; frontoclypeal suture a narrow groove, tentorial pits indistinct in a larger depression; anterior clypeus with 3 grooves (laterally and medial), 1 setose puncture each side bearing 2 setae, rarily with medial puncture ( Fig. 52 ). Labrum lobate, anterior edge moderately emarginated with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded ( Fig. 12F ), process broad and short, moderately angled upward (30°), moderately indentate ( Fig. 12B ); mentum setae ( Fig. 8 ) absent.

Submentum sclerite constriction broad with 6 setae evenly-spaced laterally (large gap medially). Stipes with 2 basal setae. Gula pits indistinct, suture well-defined, gula flat with fine transverse lines. Gena ( Fig. 8 ) with a fine isodiametric pattern across entire area.

Prothorax: Prothoracic carina narrow the entire length (broadened at shoulder), slightly crenulated with 8–12 setae ( Fig. 52 ) each side (last posterior setae just anterad foveae), extended beyond anterior angle; posterior sinuation indistinctly carinate, slightly angled inward; pronotum broad and deflected laterally, overall shape cordate ( Fig. 52 ); midline well-defined, anterior medial and posterior medial diamond-shaped impressions, disc covered with fine transverse wrinkles ( Fig. 52 ); pronotal foveae broad and shallow; anterior and posterior edges straight. Prosternum flat and smooth; proepisternum without microsculpture. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Broad and slightly deflected laterally; humeral angle evenly convex ( Fig. 6B ); basal margin slightly curved and gently sloped to base, interval 1 extended to margin; lateral carina narrow the entire length, extended beyond humeral angle; humerus with 3 setose punctures proximate the angle, 4 th puncture double-spaced (or more) posterad ( Fig. 52 ); suture well-defined but no more so than striae; striae with very small, asetose punctures, evenlyspaced the entire length, more distinct and slightly increased in size laterally; intervals 1–6 flat, intervals 7 and 8 moderately convex, interval 9 strongly convex; interval microsculpture present as fine lines; 7 th strial setal pattern with 3–4 setose punctures in anterior ½, 5–6 setose punctures in posterior ½ ( Fig. 52 ), setose punctures large.

Ventral surface: Mesepisternum with a few shallow and rugose wrinkles; metepisternum ( Fig. 2 ) without microsculpture; setose punctures present on mesocoxa (2) and metacoxa (1–2). All abdominal ventrites lineate laterally, ventrite 2 with scattered obsolescent punctures; ventrites 3–5 with 1 setose puncture each side of midline; ventrite 6 setae present: ♂ with 1 setose puncture located at junction of straight apical edge and curve anterad, ♀ with 2 setose punctures laterally (large gap medially), setae evenly-spaced along bluntly rounded apical edge; lateral foveae absent. Anterior metaventrite process ( Fig. 2 ) a short rounded triangle with a very broad carina the entire length.

Male genitalia: Apical portion of penis lobe asymmetrically hooked and overall width narrow ( Fig. 52 PL) with a distinct deflection to right of vertical axis (VV) ( Fig. 15A ); ventral edge of penis lobe curved downward to form bluntly rounded ventral process that is approx. the same vertical length as dorsal process ( Fig. 52 PL) but slightly forward of vertical centre ( Fig. 3 ); apex curved symmetrically upward to form dorsal process that is relatively short and narrow, a flat-rounded hook without recurve, a short straight back edge descended as defined curve to shaft ( Fig. 52 PL); shaft of penis lobe straight (VV), narrowed in anterior ½, broadened basally; overall length of penis lobe distinctly curved ventrally (LV) ( Fig. 16C ). Structures of the endophallus ( Fig. 4 ): lateral form of the apex of central spicule pointed; dorsal form of the apex of central spicule greatly expanded with projection; setal (scales) coverage of the apical plate moderate (26–75%); size of left flange small; size of right flange large and extended (long). Left paramere basal lobe rectangular with very large anterior dorsal hump forming a moderately steep (45°) slope to arm; arm short and broad ( Fig. 52 LP); terminal lobe short and broad (slightly broader than arm) with apical tuft of sparse medum-lengthed setae; setae extended along arm to long-lengthed and denser comb to armbasal lobe junction ( Fig. 52 LP); setae extended along apical ½ of straight ventral edge. Right paramere narrowly rectangular with setae extended along apical ½ of ventral edge ( Fig. 52 RP), moderately inwardly curved apically.

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

Comments: Mecodema scitulum was synoymised by Britton (1949) under M. spiniferum , a species only found the Waitakere Ranges, northwest Auckland. However, M. scitulum is a distinct species that is found only in the northwestern areas of the Hunua Range.

Distribution: New Zealand, North Island, AK, northwestern Hunua Range (Clevedon), i.e. northern Wairoa (Broun).

Holotype: BMNH male labelled. Type [round label with red border] / 2593 ♂ / New Zealand [red underline] Broun Coll. Brit. Mus. 1922-482. / Northern Wairoa [hw] / Mecodema scitulum [hw] / card-mounted male genitalia.

Material examined: 4, NEW ZEALAND, AK, Mataitai Forest SA , pitfall E1, Jan 2002, A. Warren / AMNZ 61476 , 61475 , 59714 , 59713 ; 3, NEW ZEALAND, AK, Mataitai Forest SA , pitfall E23, Jan 2002, A. Warren / AMNZ 59993 , 59715 , 59994 ; 1, NEW ZEALAND, AK, Mataitai Forest SA , pitfall C11, Jan 2002, A. Warren / AMNZ 61474 ; 2, NEW ZEALAND, AK, Mataitai Forest SA, pitfall A23, Jan 2002, A. Warren / AMNZ 59077 , 62102 ; 1, NEW ZEALAND, AK, Mataitai Forest SA, pitfall F23, Jan 2002, A. Warren / AMNZ 59992 ; 1, NEW ZEALAND, AK, Mataitai Forest SA, pitfall A11, Jan 2002, A. Warren / AMNZ 59085 ; 1, NEW ZEALAND, AK, Mataitai Forest SA, pitfall A13, Jan 2002, A. Warren / AMNZ 61473 ; 3, NEW ZEALAND, AK, Mataitai Forest SA, pitfall E1, Feb 2002, A. Warren / AMNZ 61441 , 61439 , 61440 ; 3, NEW ZEALAND, AK, Mataitai Forest SA, pitfall E5, Feb 2002, A. Warren / AMNZ 61479 , 61478 , 61480 ; 1, NEW ZEALAND, AK, Mataitai Forest SA, pitfall F3, Feb 2002, A. Warren / AMNZ 61442 ; 1, NEW ZEALAND, AK, Mataitai Forest SA, pitfall A3, Feb 2002, A. Warren / AMNZ 61477 ; 1, NEW ZEALAND, AK, Mataitai Forest SA, pitfall E11, Feb 2002, A. Warren / AMNZ 61481 ; 2, NEW ZEALAND, AK, Mataitai Forest SA, pitfall E1, Mar 2002, A. Warren / AMNZ 61486 , 61481 ; 2, NEW ZEALAND, AK, Mataitai Forest SA, pitfall E13, Mar 2002, A. Warren / AMNZ 61488 , 61489 ; 2, NEW ZEALAND, AK, Mataitai Forest SA, pitfall E21 and E25, Mar 2002, A. Warren / AMNZ 61490 ; 1, NEW ZEALAND, AK, Mataitai Forest SA, pitfall E1, Mar 2002, A. Warren / AMNZ 61485 ; 1, NEW ZEALAND, AK, Mataitai Forest SA, pitfall C3, Mar 2002, A. Warren / AMNZ 62103 ; 1, NEW ZEALAND, AK, Mataitai Forest SA, pitfall A25, Mar 2002, A. Warren / AMNZ 61484 ; 1, NEW ZEALAND, AK, Mataitai Forest SA, pitfall A23, Mar 2002, A. Warren / AMNZ 61483 ; 1, NEW ZEALAND, AK, Mataitai Forest SA, pitfall A11, Mar 2002, A. Warren / AMNZ 61482 .

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 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 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 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 52. Mecodema scitulum 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.