Dichotomius sericeus (Harold), 1867

Valois, Marcely C., Vaz-De-Mello, Fernando Z. & Silva, Fernando A. B., 2017, Taxonomic revision of the Dichotomius sericeus (Harold, 1867) species group (Coleoptera: Scarabaeidae: Scarabaeinae), Zootaxa 4277 (4), pp. 503-530 : 507

Dichotomius sericeus (Harold) species group

“Section sericeus ”; Luederwaldt, 1929: 81 (description and identification key).

“ Dichotomius sericeus species group”; Vaz-de-Mello, 2001: 100 (taxonomic remarks); Nunes & Vaz-de-Mello, 2013: 418 (identification key to the species groups of Luerderwaldtinia)

The species of the Dichotomius sericeus group are placed in the subgenus Luederwaldtinia Martínez, 1951 . The morphological

characters described to the subgenus can be verified in the recent literature (Vaz-de-Mello et al., 2011; Nunes & Vaz-de-Mello,

2013; Maldaner et al., 2015).

Diagnosis. Since Luederwaldt (1929) proposed the section sericeus (= Dichotomius sericeus species-group), it has been easily distinguished between Luederwaldtinia species by a deep fovea at the pronotum posterior angles; fovea comma-shaped, often bearing a small tubercle anteriorly and orange setae inside ( Fig. 4 a, arrows). This character is unique among Dichotomius species and related genera.

Description. Length: 11–17 mm. Body black with glossy bluish or purplish sheen; convex ( Fig. 11 a) or slightly flattened dorsoventrally in lateral view ( Fig. 11 b) with orange setae on ventral surface. Head: wider than long, semicircular, with strong central margination, clypeo-genal junction not angled. Clypeus with two rounded, subtriangular and short teeth, separated by V-shaped emargination. Clypeal surface usually covered by punctures on males and transversal ridges on females. Ventral clypeal process conical with bifurcate apex. Clypeogenal suture present, straight. Genal surface covered by ocellate punctures and/or radial ridge. Dorsal interocular surface with large and dense ocellate punctures. Frons bearing one conical horn, usually with two knobs near each eye or lacking horn, bearing only three weak knobs (as in D. schiffleri ). Dorsal interocular distance approximately four times eye width. Central portion of posterior margin of head shiny, surrounded by ocellate punctures. Antennal club yellow, covered by short and yellow pubescence, thin and dense, with long orange setae interspersed. Pronotum: approximately two times wider than long; lateral margins rounded; dorsal surface convex in lateral view. Hypomera: anterior and posterior portion divided by convex and smooth area; anterior portion with ocellate and setigerous punctures, setae long; posterior portion with elliptical punctures with short setae. Lateral margins with row of setae, visible in dorsal view. Metasternum: central portion of disc smooth, with longitudinal sulcus medially, depressed in posterior portion. Anterior portion punctuate near meso-metasternal suture; lateral portion with large ocellate and setigerous punctures, setae long. Legs: anterior and posterior margins of profemur and posterior margins of meso- and metafemur all with longitudinal sulcus; surface of sulcus with well-defined microsculpture. Mesotibia and metatibia abruptly widened apically. Metatibia obliquely truncated apically, external edge denticulate. Elytra: bicarinulate elytral striae, punctuate; punctures wider than striae and separated by twice their diameter. Interstriae convex, with disperse and inconspicuous microgranulation, dense punctate punctures or wrinkled surface. Abdomen: medial portion of sternites shiny, or with a single row of punctures along the anterior portion; lateral portions of sternites bearing dense ocellate punctures on its anterior border; sternites shiny posteriorly. Male medial portion of sixth sternite half as long as the fifth. Aedeagus: parameres symmetric, 2/3 shorter than phallobase (Fig. 1a). Endophallus: lamella copulatrix (LC) stirrup-shaped (Fig. 1c). Superior-right peripheral sclerite (SRP) semicircular (Fig. 1b). Fronto-lateral peripheral sclerite (FLP) comma-shaped with a anterior projection (Fig. 1b). Sclerites of axial and subaxial (A+SA) complex elongated and curved; sclerites narrowed toward the apex; apical portion of A+SA complex cylindrical and hollow (Fig. 1b). Secondary sexual characters: in all species of the D. sericeus group the females differ from males by presenting more acute clypeal teeth, medial portion of sixth sternite as long as the fifth and occasionally by the presence of well-defined transversal ridges on the clypeal surface.

Taxonomic remarks. Within Luederwaldtinia , the Dichotomius sericeus group shares the puncture pattern of the interocular space, ventral surface of profemur and surface of abdominal sternites, as well, the presence of a well-defined sulcus on posterior margin of meso — and metafemur with D. globulus ( Felsche, 1901) , D. batesi (Harold, 1869) , D. fortestriatus (Luederwaldt, 1924) and D. ziliolli Gandini & Aguilar, 2009 [ D. batesi speciesgroup]. The pattern of metasternum puncture and pilosity in D. sericeus ( Harold, 1867) and D. irinus ( Harold, 1867) resembles that on D. carbonarius species-group.

Distribution. Known from Brazil, Paraguay and Argentina. Most records are from the Brazilian coast where the species occurs in areas of the Atlantic rainforest, Restinga and Caatinga ( Fig. 12 a–d). Only Dichotomius sericeus reaches the Atlantic rainforest in Paraguay and Argentina ( Fig. 12 a).

Ecological information. The species has been cited in the ecological literature as coprophagous ( Filgueiras et al., 2009; Campos & Hernandez, 2013) or generalist ( Culot et al. 2013; Hernandez et. al., 2014). Specimens were associated with closed habitats of Atlantic rainforest and the species is abundant in the communities effaced by habitat loss and fragmentation ( Endres et al. 2007; Costa et al. 2009; Silva et al. 2010; Filgueiras et al. 2011; Costa et al., 2013; Culot et al. 2013).

Figures

FIGURE 4. Dichotomius laevicollis (Felsche, 1901). a— body, dorsal view (fovea on posterolateral portion of pronotum, arrows); b— head, male; c— head, female; d— pronotum (rounded ocellate punctures closer to posterior margin, arrow); epronotum detail (lateral margin, arrow). Aedeagus. f— lateral view; g— ventral view; h— dorsal view.

FIGURE 11. External morphology of D. sericeus species group. a— Dichotomius sericeus (Harold, 1867), body, lateral view; b— D. schiffleri Vaz-de-Mello, Gavino & Louzada, 2001, body, lateral view; c— D. sericeus, detail of posterior margin of meso and metafemur, arrows; d— D. schiffleri, detail of posterior margin of meso and metafemur, arrows; e— D. sericeus, mesotibia, ventral view (row of setae toward the body, red arrow); f— D. irinus, mesotibia, ventral view (row of setae toward the body, red arrow); g— D. irinus, pygidium; h— D. sericeus, pygidium.

FIGURE 12. Known distribution of D. sericeus species group. a— Dichotomius sericeus (Harold, 1867) and Dichotomius iannuzziae sp. nov.; b— Dichotomius irinus (Harold, 1867) and Dichotomius guaribensis sp. nov.; c— Dichotomius laevicollis (Felsche, 1901) and Dichotomius gilletti sp. nov.; d— Dichotomius schiffleri Vaz-de-Mello, Gavino & Louzada, 2001 and Dichotomius catimbau sp. nov.