Mecodema, Blanchard, 1853

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 : 13

Genus Mecodema description

Head, frons and vertex often rugose and / or punctate, microsculpture or macrosculpture absent in some species groups (e.g., curvidens species); eyes prominent, almost hemispherical ( Figs 1 and 9 ); a single supraorbital puncture on each side, bearing more than one setae; setose punctures of vertex absent; mandibles large, uniformly narrow to the pointed apex, sharply curved in the apical third ( Fig. 9 ), mandibles with a number of dorsal grooves and without a seta in the scrobe; mentum with median process, which is notched to strongly indentate (bifid) ( Fig. 8 ); usually with 2 setiferous punctures (may be absent) below the process and generally with 4–8 setose (setiferous) punctures along the submentum sclerite ( Fig. 8 ); labial palpi with setae on the penultimate segment; terminal segments of all palpi slightly compressed, sub-cylindrical, truncate; ligula chitenous with a median carina, 2 apical setae present; the membranous paraglossae extended well beyond the apex of the ligula; stipes with 2–3 basal setae; antennomeres I–II glabrous, III–V with apical ring, VI–XI setose throughout; antennomeres I–III subcylindrical, IV–VII subglobose and slightly compressed. Prothoracic carina (pronotal lateral margin) distinct with an asymmetrical number of setae along each side ( Fig. 11 ), the last never at the posterior lateral sinuation (posterior angle); midline (median groove) and pronotal foveae (laterobasal depressions) always present ( Fig. 11 ); pronotal disc often with shallow depressions on each side of apical half. Elytra always striate; fused together along the suture; hind wings absent; a row of setose punctures on the 7 th stria ( Fig. 1 ) and another row (umbilical series) near the lateral carina (elytral margin). Legs slender, the protibia with a pointed apical prolongation on the outer side, greatly distally expanded ( Fig. 10A ) to distally expanded ( Fig. 10B ) and shovel-like; male and female tarsi identical, the basal 4 segments of the anterior tarsi are as broad as they are long, usually slightly asymmetrical. Type species: M. sculpturatum Blanchard 1853 .

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 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.