Caenolethrus Grossi & Paulsen

Grossi, Paschoal C., 2009, Generic limits in South American stag beetles: taxa currently misplaced in Sclerostomus Burmeister (Coleoptera: Lucanidae: Lucaninae: Sclerostomini), Zootaxa 2139, pp. 23-42 : 36-37

Caenolethrus Grossi & Paulsen , new genus

Type species: Sclerostomus varasi Nagel, 1932: 115 , HERE DESIGNATED.

Description. Length: 14.6–17.1 mm. Width: 6.5–7.5 mm. Head: Form not enlarged, width subequal to width of one elytron in both sexes. Vertex roundly excavated from anterior angles to base; excavation punctate; punctures dense, coarse. Margin of excavation strongly elevated above antennal insertions, punctate; punctures moderate, dense, decreasing in size and density with elevation. Gena as wide as eye, shorter than eye in dorsal aspect; lateral margins nearly parallel, not continuous with anterior angle of head. Anterior margin of frons not strongly declivous before labrum. Labrum prominent in both sexes. Mandibles in males not longer than head, apices not strongly curved upward, tridentate including apex; teeth acute. Mandibles of females simple, apices acute with single internal tooth. Lacinia sclerotized, hook-like. Antennomeres of club mainly glabrous but with scattered setae; distal antennomere less than half tomentose; tomentosity confined to apex. Pronotum: Shape broad, explanate, widest at basal third before narrowing to produced basal angle. Disc elevated anteriorly before declivous anterior face in males, anterior elevation punctate; punctures increasingly fine with elevation; disc not elevated anteriorly in females. Median depression large, longitudinally ovoid, acute anteriorly, bisecting anterior elevation, punctate; punctures becoming coarse medially and at base, largest punctures with scales. Anterior angles rounded, subtriangular, projecting. Lateral margins broadly rounded anterolaterally, beaded, with band of oval scales. Elytra: Form broad, suboval, flattened overall (Fig. 12). Disc punctate; size and density of punctures varying from scarce and fine on disc near suture to coarse and nearly contiguous on apical declivity. Lateral margin subexplanate, with band of oval scales; band similar in width to scale band of pronotum. Wings: Fully developed. Legs: Mesotibiae and metatibiae each with only a single external tooth at about middle. Apex of metatibia acute in males, truncate in females. Male genitalia: Genital capsule and aedeagus simple, lacking additional lobes. Everted internal sac distally enlarged, medially with an area of dense, dark pubescence (Fig. 7).

Distribution. Chile: Regions of Maule and Biobío.

Etymology. Nothing is known about the life history of these beetles, as they have been rarely collected alive. Most of the few specimens that have been found were dead on the ground, and it is possible that the adults are found in dead wood that is infrequently collected and high off the ground ( Paulsen 2005). The name is derived from the Greek caeno (recent) and olethros (death), to approximate ‘recently deceased,’ as most specimens are when encountered. The gender is masculine.

Diagnosis. This genus is easily distinguished by its flat and broad form, lack of tubercles or horns on the pronotum, non-uniform punctation on the elytra, and the presence of well-defined, wide lateral band of oval scales on the pronotum and elytra. The male mandibular form and male genitalia are unique among the Sclerostomini, in particular the everted internal sac is inflated and densely pubescent.