Dichotomius (Luederwaldtinia) mysticus (Luederwaldt)

Nunes, Rafael V. & Vaz-De-Mello, Fernando Z., 2013, New brachypterous species of Dichotomius Hope, with taxonomic notes in the subgenus Luederwaldtinia Martínez (Coleoptera: Scarabaeidae: Scarabaeinae), Zootaxa 3609 (4), pp. 411-420 : 413-415

Redescription of Dichotomius (Luederwaldtinia) mysticus (Luederwaldt)

Pinotus (Selenocopris) mysticus, Luederwaldt 1935 (original description)

Pinotus mysticus, Blackwelder 1944

Dichotomius (Luederwaldtinia) mysticus , Vaz-de-Mello 2000 (new combination)

Material studied: Holotype: Ƥ Natal ( Brasilien). W.M. Mann [NHML]; 2Ƥ, 3 BRASIL: Rio Grande do Norte: Natal. Parque das Dunas. 5º48’35’’S; 35º11’28’’W. hum faec. 18.V.2011. MEMaldaner [CEMT]; 1 3 same data but 15.III.1998. O.Câmara. [CEMT]; 4 3, 2 Ƥ same but 15.III.1991. [CEMT, UFRN]; 2 3 3, 5 Ƥ same data but 16.III.1991. [CEMT]; 1 3, 1 Ƥ same data but 16.III.1991 [CEMT]; 1 3, 1 Ƥ same data but 13.IV.1991 [CEMT]; 2 3 same data but 17. V.1991 [CEMT]; 2 Ƥ same data but 15.VI.1991 [CEMT].

Diagnosis. Among Luederwaldtinia species, D. mysticus belongs to the D. geminatus species group due the combination of the following characters: head with single central tubercle, pronotum with an anterior single central lobe and hypomeron with a lateral band of ocellate punctures bearing abundant, red pilosity, that can be seen dorsally ( Fig 1 A). Within this species group, D. mysticus is the only brachypterous species; as such, the pronotum is wider than the elytra, the humeral callus is absent, the elytra are strongly convex, and hind wing never reaches the length of the elytra. In addition, the mesotarsi, metatarsi, and tarsal claws are covered with a dense, red pilosity ( Fig. 1 D).

Males: Length: 11–13 mm. Maximum width (pronotum): 6.0–7.5 mm. Black, shiny, with feeble blue sheen on base of elytra of some specimens. Head: semicircular, surface almost smooth, with few ocellate punctures near each eye. Clypeogenal junction evenly rounded, lacking angulation, with weak emargination. Ventral clypeal process bifurcated. Clypeofrontal region with a single, central tubercle. Antennal club with dark red or light brown tumescence. Clypeal and genal lateral margins with a ventral row of small, red setae that increase in length from the middle of head laterally. Pronotum: length equal to width; wider than elytra. Disc smooth, shiny, with indistinct punctures (only seen with 20x magnification); ocellate punctures present along posterior border and on lateral and anterior angles. Anterior margin widened in the middle forming a triangular projection. Pronotal disc with central knob anteriorly. Anterior angles rounded. Hypomeron: with a lateral band of ocellate punctures bearing abundant, red pilosity; narrowest medially and reduced to single medial row (setae in the single row about one half the length of setae on anterior and posterior portion). The lateral red pilosity may vary in abundance. Hypomeron glabrous, shiny medially. Prosternum: with ocellate, setose punctures. Mesosternum: weakly narrowed, shiny, glabrous between mesocoxae, with ocellate punctures and pilosity above coxae. Mesepisternum: with ocellate, setose punctures evenly distributed on surface, Metasternum: portion between mesocoxae widened apically, width twice that between apices of coxae, with ocellate punctures anteriorly and laterally and posterior depression. Elytra: shiny with blue sheen anteriorly on some males; discal striae distinctly punctate, punctures wider than striae and separated by double its width. Lateral (ninth) stria not reaching the base. Elytral interstriae shiny, feebly convex. Legs: bearing abundant red pilosity on tibia and tarsi, including around tarsal claws ( Fig. 1 D). Protibiae with three well-defined teeth, and feebly developed fourth (basal) indicated by a sinuosity. Ventral surface of profemur with three rows of setose, ocellate punctures. Apical fifth of protibial spur strongly curved inward. Ventral surface of mesofemur with ocellate punctures near tibial articulation. Metatibial spur flattened, subapically dentate. Hind wing: articulated and foldable, reduced (length 6.5 mm). Basal sclerites glabrous. Subcostal vein intersecting costal axis at its basal quarter. Medial vein extending to the folding articulation. Distinct pilosity present on the basal third of costal axis and on folding region. Cubital vein present, anal vein absent. Small developed membranous portion apical to folding articulation with incomplete or weakly-marked venations ( Fig. 1 C). Abdomen: with sixth sternite strongly narrowed medially and bearing small medial protuberance. Pygidium: wider than long, shiny and glabrous. Ocellate punctures present only basally. Phallobase: dorsally, with apical border curved. Parameres: almost symmetrical, truncate, and apically flattened (on lateral view).

Females: length varies from 11.0–12.5 mm. Pronotum width varies from 6.0–7.5 mm. Females differ from males as follows: Head: clypeus completely transversally ridged. Ocellate punctures more conspicuous near eyes. Frontoclypeal junction with a pair of closely-positioned medial tubercles. Frons with median curved depression delimited anteriorly by a C-shaped transverse elevation. Pronotum: lacking knobs or declivities. Hypomeron: setae longer and denser than in males. Abdomen: sixth abdominal sternite medially double the width of other abdominal segments.

Distribution and conservation. Natal, Rio Grande do Norte, northeastern Brazil. In addition to the holotype, a female was collected at an unspecified locality in Natal and other specimens were collected at Parque Estadual das Dunas Costeiras, a conservation unit in the city of Natal. Parque das Dunas is severely affected by urban growth and fire ( Freire 1990). Since, D. mysticus is flightless and may have a restricted, vulnerable habitat, the conservation status bears further investigation.

Systematics. At the time of its description, this species was placed in the D. inachus species group ( Luederwaldt 1935). However, with a new definition of Luederwaldtinia species groups within this work, we suggest that this species belongs to the D. geminatus species group based on pronotum, head, and pilosity characters (see diagnosis and key for the species groups). The D. geminatus species group is composed of D. mysticus , D. geminatus , and D. opacipennis .

Ecological information. Three specimens were associated with tree sand dune habitats in the city of Natal. They were caught using pitfall traps baited with human feces. Other specimens were collected between March and June but lack ecological data.

Figures

FIGURE 1. Dichotomius mysticus (A) dorsal habitus; (B) dorsal view of genitalia; (C) hind wing; and (D) tarsi and tarsal claw (indicated by black arrow). Dichotomius vidaurrei (E) dorsal habitus; (F) dorsal view of genitalia; and (G) hind wing. Scale bar = 1.5 mm.