Mecodema rusticulus, 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 : 101-104

Mecodema rusticulus sp. n.

Figure 51 .

Diagnosis: Differs from other North Island Mecodema species by: 1, the small supraorbital puncture (may consist of 2–3 separate punctures) bearing 4–5 setae; 2, the elytral striae with small, regularly spaced, asetose punctures, some obsolescent laterally; 3, the discus-shaped shape of the apical portion of the penis lobe ( Fig. 51 PL).

Description: Length 25.3–33.5 mm, pronotal width 7–8.6 mm, elytral width 8.2–10.3 mm. Colour of entire body matte to glossy black, coxae to tarsi dark reddish-brown to black.

Head: Broad and moderately convex ( Fig. 14B ). Vertex with fine lines forming an isodiametric pattern; vertexal groove defined by sparsely distributed punctures, laterally broad ( Fig. 51 ); small supraorbital puncture (may consist of 2–3 separate punctures) bearing 4–5 setae; 3 or more poorly defined supraorbital grooves that may extend onto lateral area of frons; frons medially convex with a large and shallow depression each side of midline; frontoclypeal suture and tentorial pits indistinct; anterior area of clypeus ( Fig. 9 ) with broad, well-defined grooves, l setose puncture each side bearing 1–2 setae ( Fig. 51 ), central puncture bearing 2 setae (some specimens without central setose puncture). Labrum rectangular, anterior edge outwardly curved, moderately emarginated medially with 2 proximate central setae, 2 setae each side evenly spaced. Mentum lobes rounded ( Fig. 12F ), median process very short and broad, slightly angled upward (15°) moderately indentate ( Fig. 12B ); mentum setae absent. Submentum sclerite constriction broad with 6 regularly spaced setae. Stipes with 2 basal setae. Gula pits ( Fig. 8 ) small to indistinct, suture indistinct, gula flat with transverse lines. Gena with fine lines forming an isodiametric pattern across entire area.

Prothorax: Prothoracic carina ( Fig. 11 ) narrow the entire length, crenulations absent with 7–11 setae each side, extended beyond anterior angle; posterior lateral sinuation evidently carinate, slightly angled inward; pronotum broad and deflected laterally, overall shape cordate ( Fig. 51 ); midline well-defined, anterior medial triangular impression and posterior medial diamond-shaped impresson present, disc with fine transverse wrinkles laterally; pronotal foveae shallow and broad; anterior edge slightly inwardly curved, posterior edge straight. Prosternum flat with fine transverse lines; proepisternum without microsculpture. Procoxal setae absent; protibia distally expanded and shovel-like ( Fig. 10B ).

Elytra: Broad and slightly deflected laterally; humeral angle anteriorly convergent ( Fig. 6A ); basal margin slighly curved and gently sloped to base, interval 1 extended to margin; lateral carina narrow the entire length, extended to humeral angle; humerus with 3–4 proximate setose punctures, 4 th or 5 th double-spaced posterad ( Fig. 51 ); suture poorly impressed; striae with small, regularly spaced, asetose punctures, some obsolescent laterally; intervals 1–6 weakly convex, intervals 7–9 moderately convex, interval microsculpture present in form of very fine transverse lines; 7 th strial setal pattern with 3 setose punctures in anterior ½, 5 setose punctures in posterior ½ ( Fig. 51 ), setose punctures large.

Ventral surface: Mesepisternum ( Fig. 2 ) and metepisternum without microsculpture (may be a few fine lines); setose punctures present on mesocoxae (2) and metacoxae (2). Abdominal ventrites 1 and 2 without lines; ventrites 3–5 finely lineate, 1 setose puncture each side of midline; ventrite 6 setae present: ♂ with 1 setose puncture each side at junction of straight apical edge and curve to anterior, ♀ with 2–3 setose punctures each side along bluntly pointed apical edge; lateral foveae absent. Anterior metaventrite ( Fig. 2 ) rounded with nipple-like extension, carina apically broad but narrowed significantly toward coxa.

Male genitalia: Apical portion of penis lobe discus-shaped, asymmetrically rounded with very distinct deflection to right of vertical (VV) ( Fig. 15A ); ventral process a bluntly, rounded point (Dome Valley) to sharply pointed in specimens from Pukekororo S.R. and Logues Bush S.R., dorsal process slightly flattened proximate the shaft ( Fig. 51 PL), shaft of penis lobe narrowed toward discus-shaped apical portion, especially dorsally, ventral edge of penis lobe straight (VV); overall length of penis lobe moderately curved ventrally (LV) ( Fig. 16B ). 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 without projection; setal (scales) coverage of the apical plate extensive (76–100%); size of left setose flange small; size of right setose flange very large. Left paramere basal lobe rectangular with large dorsal hump that forms steep angle (60°) to arm ( Fig. 51 LP); arm narrow and very short; apical lobe slightly broadened than arm but same length as arm, apical tuft of sparse, short setae, then a small number of short setae in junction curve of basal lobe and arm ( Fig. 51 LP); ventral edge of basal lobe straight. Right paramere long, narrowly triangular with a double row of long setae extended along apical ¾ of ventral edge ( Fig. 51 RP); apical ⅓ slightly inwardly curved toward penis lobe.

Female genitalia: Basal gonocoxite 1 long and broad (broadened apically), ventral surface with a few rugose wrinkles, internal dorso-lateral carina with 3 setae. Gonocoxite 2 ( Fig. 5 ) ovate, slightly reflexed apically. Ramus long and broad.

Comments: Mecodema rusticulus ranges from Dome Valley north to the Brynderwyn Hills, including Pukekororo S.R. and eastern forest remnants to the coast (e.g., Logues Bush). Many of these populations are not accessible due to a rahui imposed by local iwi to inhibit removal and collection of material from native forest remnants that have kauri ( Agathis australis ) trees affected by kauri dieback disease.

Distribution: New Zealand, North Island, Auckland, northern Rodney District, Logues Bush S.R., Pukekororo S.R., Dome Valley S.R.

Holotype: NZAC, male labelled. NEW ZEALAND AK, Logues Bush S.R. 24 II–02 III 1999 #1106, 1108 P. Paquin & N. Dupérré / Pitfall traps Moist podocarp x broadleaf forest Landscape Patch Dynamic Project / HOLOTYPE Mecodema rusticulus n. sp. design. DS Seldon, TR Buckley 2018 [red label].

Paratypes: 1♀, NEW ZEALAND AK, Logues S.R. 22–29 XII 1998 #205 # 243 P. Paquin & N. Dupérré / Pitfall traps. Moist podocarp x broadleaf forest Landscape Patch Dynamic Project ( NZAC) ; 1♀, NEW ZEALAND AK, Logues Bush S.R. 03–10 II 1999 # 818 P. Paquin & N. Dupérré / Pitfall traps Moist podocarp x broadleaf forest Landscape Patch Dynamic Project ( NZAC) ; 1♀, NEW ZEALAND AK, Logues Bush S.R. 17–24 II 1999 #1013 P. Paquin & N. Dupérré / Pitfall traps Moist podocarp x broadleaf forest Landscape Patch Dynamic Project ( NZAC) ; 1♀, 1♂, NEW ZEALAND AK, Logues Bush S.R. 02– 09 III 1 999 #1205, #1201 P. Paquin & N. Dupérré / Pitfall traps Moist podocarp x broadleaf forest Landscape Patch Dynamic Project ( NZAC) ; 1♀, NEW ZEALAND AK, Logues S.R. 30 III- 06 IV 1 999 #1586 P. Paquin & N. Dupérré / Pitfall traps Moist podocarp x broadleaf forest Landscape Patch Dynamic Project ( NZAC) ; 1♂, NEW ZEALAND AK, Logues Bush S.R. 24 II–02 III 1999 #1106, 1108 P. Paquin & N. Dupérré / Pitfall traps Moist podocarp x broadleaf forest Landscape Patch Dynamic Project ( NZAC) ; 3♂, NEW ZEALAND AK, Logues S.R. 26 I–03 II 1999 #722 (2) , 723 P. Paquin & N. Dupérré / Pitfall traps Moist podocarp x broadleaf forest Landscape Patch Dynamic Project ( NZAC) ; 1♀, NEW ZEALAND AK, Logues Bush S.R. 09–16 III 1999 #1298 P. Paquin & N. Dupérré / Pitfall traps Moist podocarp x broadleaf forest Landscape Patch Dynamic Project ( NZAC) ; 1♀, NEW ZEALAND AK, Pukekaroro Sce. Res. , 3613 S 17444 E, 150 m, 12.XI–10.XII 2001, Larivière. Larochelle / wet podocarp x taraire forest, steep slopes pittraps ( NZAC) ; 1♂, NEW ZEALAND AK, Pukekaroro Sce. Res. , 3613 S 17444 E, 150 m, 15.X–12.XI 2001, Larivière. Larochelle / wet podocarp x taraire forest, steep slopes pittraps ( NZAC) ; 3(♂, ♀), NEW ZEALAND AK, Dome Valley walkway, 3637 S 17462 E, 200 m, 10.XII 2001– 14.I.2002, Larivière. Larochelle / wet tree fern forest, steep slopes ( NZAC) ; 2(♂, ♀), NEW ZEALAND AK, Dome Valley walkway, 3637 S 17462 E, 200 m, 12. XI–10.XII 2001, Larivière. Larochelle / wet tree fern forest, steep slopes ( NZAC) ; 3♂, 2♀, NEW ZEALAND AK, Dome Valley walkway, 3637 S 17462 E, 200 m, 15.IX–15.X 2001, Larivière. Larochelle / wet tree fern forest, steep slopes ( NZAC) ; 1♂, NEW ZEALAND AK, Warkworth Dome Valley 14 Jan 1997 S.E. Thorpe ( NZAC) ; 1, NEW ZEALAND AK, Warkworth Dome Valley 2 Feb 1997 S.E. Thorpe ( NZAC) ; 1♂, Dome Valley bush near Warkworth 17.11.44 B.B. Given ( NZAC) ; 1 [card mounted], NEW ZEALAND AK, Mt Dome nr Warkworth 26.11.95 MB Nunn / J. Nunn Collection ( NZAC) ; 1♂, NEW ZEALAND, ND Brynderwyns , 25 Aug 1989 PJ Anderson / NZMS 260 Q08 427 683 in leaf / AMNZ 40704 [green label]; 1, Matakana Nth Auck. Oct 1959 V.A Nicholls [hw] / AMNZ 84329 [green label] .

Etymology: As this species is found in native forests in the most northern areas of the Auckland supercity, more rural than urban, so it is named rusticulus, meaning yokel.

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 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 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 51. Mecodema rusticulus 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.