Apterodorcus Arrow

E, José Mondaca, 2008, Revision of the genus Apterodorcus Arrow (Coleoptera: Lucanidae: Lucaninae) of southern South America, Zootaxa 1922, pp. 21-32 : 23-24

Genus Apterodorcus Arrow

Apterodorcus Arrow 1943: 139 . Type species: Lucanus bacchus Hope in Westwood, 1845, by monotypy.

Description. Scarabaeoidea: Lucanidae : Lucaninae : Sclerostomini. Length: 19.2–35.4 mm. Width: 9.0–14.5 mm. Color: Black, surface alutaceous, weakly shiny or opaque, lacking iridescence. Vestiture: Apparently glabrous dorsally; minute scales visibly only at 40X near elytral apex; scales arising centrally in elytral punctures, form branched; branches tapering to acute apex ( Fig. 12 in Holloway 1997). Head: Eyes partially divided by ocular canthus. Frons more or less flat, weakly excavated anteromedially, excavation parabolic; lacking anteromedial tubercle, sparsely to moderately punctate; punctures fine to moderate, becoming larger and more dense anteriorly and laterally, punctation markedly stronger and denser in female. Suprantennal gibbosity weakly developed. Both sexes with strongly developed, lobelike temporal process. Labrum setose, projecting anteriorly, appearing trilobed or rounded; median lobe subtuberculate in males. Male majors with mandibles usually as long as head, curved abruptly before apex, apex bifurcate with teeth acute; internally near middle with 2–3 obtuse teeth; dorsally with tooth near base. Male minors with mandibles similar to male major in dentition but everywhere smaller. Male laciniae lacking hook. Female mandibles complex, left mandible with 4 teeth (dorsal, apical, ventral, internal), right mandible with 3 teeth (dorsal, apical, ventral); dorsal surface flat or with external dorsal carina more or less produced. Female laciniae with sclerotized hook. Antennae with 10 antennomeres, geniculate, with asymmetrical, immobile club of 3 antennomeres; club mostly tomentose distally, glabrous on stem. Pronotum: Form broadly rounded externally or subparallel, weakly angulate in basal third, width at base narrower than elytra, broader than elytra anteriorly. Disc convex, not flattened medially. Anterior angle obtuse, sides; margin straight from angulation to posterior angle. Margins beaded (bead obsolete anteromedially), shining, not reflexed. Surface punctate; punctures fine to moderate on disc, becoming large and coalescing near margins. Scutellum: Form parabolic or triangular. Size reduced or not, occasionally weakly depressed below level of elytra. Elytra: Form convex, somewhat shorter in males (as long as head and pronotum combined), somewhat fused (but separable) at suture. Surface lacking obvious scales, weakly striate, punctate; punctures fine on disc, becoming larger and coalescing laterally and basally. Wings: Brachypterous in both sexes; wing form narrow, elongate, reaching approximately to middle of elytron. Legs: Protibiae with 4–6 large external teeth. Mesotibiae and metatibiae with large external tooth, 0–2 smaller teeth proximally. Onychium (= empodium) with brush-like, multiple setae. Male Genitalia: Form symmetrical. Male internal sac permanently everted, sclerotized, strap-like, parallel-sided to subapex; apex triangular, not expanded distally. Parameres simple, curved. Basal piece membranous posteroventrally, dorsally. Genital capsule simple (lacking additional lobes present in some sclerostomines). Female Genitalia: Similar to other sclerostomines. Illustrated by Weinreich (1960: Fig. 68).

Diagnosis. This genus is distinguished from other New World lucanine genera by the following combination of characters: antennae with club of 3 antennomeres, with club mostly tomentose; onychium of last tarsal segment brush-like with more than 10 setae (not 2–4 setae as in all other New World sclerostomines); head with strong, lobe-like temporal processes in both sexes; pronotum and elytra lacking obvious vestiture. Apterodorcus species can be immediately distinguished from other southern South American sclerostomines by their larger size, and black coloration without visible scales ( Apterodorcus species lack a pattern of scales on the pronotum and/or elytra commonly found in other genera of southern South American sclerostomines).

Distribution ( Fig. 1 ). Argentina and Chile, see species account below.

Remarks. This genus is more similar to species of the New Zealand genus Geodorcus than to species of other New World genera. Microscopically, it shares with Geodorcus similar elytral vestiture consisting of branched scales ( Holloway 1997). The onychium between the claws is multisetose in Apterodorcus and Geodorcus species, while in other New World sclerostomines it generally has only 2–4 setae.

Apterodorcus has been treated as monotypic with the single species A. bacchus , however the specimens from the coastal mountains south of Santiago exhibit several important differences and are not conspecific with A. bacchus . The genitalia of the two taxa do not appear to differ significantly, but they are of the simplest form found in Sclerostomini, so this may not be surprising. The second species was described by Deyrolle in Parry (1870) as Sclerostomus tristis , but probably due to its restricted range the species remained unknown to subsequent authors and it was eventually mistakenly synonymized with A. bacchus .

Figures

FIGURE 1. Distribution of Apterodorcus species: A. bacchus (circles), and A. tristis (triangles). Regions of Chile indicated by Roman numeral, provinces of Argentina by postal code (Q = Neuquén, U = Chubut, R = Río Negro).

FIGURE 12. Female A. bacchus feeding at sap flow on Nothofagus near Chillán, VIII Region.