Trichillum (Eutrichillum) arcus Solís & Kohlmann, 2003

Solís, Ángel & Kohlmann, Bert, 2003, New species of dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae) from Costa Rica and Panama, Zootaxa 139, pp. 1-14 : 10-14

Trichillum (Eutrichillum) arcus Solís & Kohlmann , sp. nov. ( Fig. 6 )

Diagnosis. This species is distinguished from other Trichillum species by the following combination of characters: metallic­colour, with head and pronotum a brilliant wine­red with green cupreous reflections, the elytra a darker wine­red with green cupreous reflections; clypeo­genal suture raised and keeled, arching and projecting towards the middle of the head, and interrupted medially.

Description. Holotype. Male: Length 3.8 mm. Humeral width 2.7 mm. Body short and rounded, dorsally convex. Dorsal surface brilliant wine­red on head and pronotum with green cupreous reflections; elytra darker wine red with green cupreous reflections; ventral surface reddish­brown. Dorsal surface with setae.

Head smooth, covered with umbilicate punctures that bear a golden seta; clypeus bidentate separated by a slightly rounded V­shaped notch, teeth well developed; genae projecting in an even arch; clypeo­genal suture raised and keeled, arching and projecting towards the middle of the head, but interrupted medially; eyes small and emarginated, 3.5 times longer than wide.

Pronotum smooth, covered haphazardly with umbilicate punctures of different sizes that bear a golden seta; postero­laterally with a small, black gibbosity; base not emarginated; pronotal lateral borders slightly angled anteriorly; an arched carina goes from behind and below the lateral gibbosity to the antero­lateral pronotal arch.

Elytra with eight striae, including the epipleural. Intervals slightly convex and smooth. Striae slightly impressed, more so at their apex, faintly punctate. First stria with a row of umbilicate punctures bearing an erect golden seta along its inner side. Striae 2­8 with the same row of punctures along the external side, with the exception of the second stria, which also has on its apical third the seta bearing punctures. Pygidium completely margined, smooth and convex, covered with umbilicate punctures of varying sizes and bearing an erect golden seta.

Femora covered by umbilicate punctures bearing an erect golden seta. Pro­, mesoepimeron, metaepisternum, pro­, meso­, metasternum and abdominal sternites covered with large, flat and shallow ocellated impressions; in the case of the metasternum the impressions lie along its margin, whereas the central area is smooth. Meso­ and metafemora have a line of punctures bearing setae at the posterior ventral margin. Like all males from the subgenus Eutrichillum it has the fifth protarsus distally swollen and dorsally deeply excavated for accommodating the claws while at rest.

Allotype. Female: Length 3.5 mm. Humeral width 2.2 mm. Similar to male, except that the fifth protarsus is not distally swollen.

Variation. Length 2.9­4.1 mm. Humeral width 1.8­2.8 mm. The first stria has sometimes one or two isolated umbilical punctures with an erect seta along its external margin. The second stria has a row of umbilical punctures with erect setae along its inner margin going from its apical third to its apical half. Strial punctures can become more crenulating towards the apex.

Examined material (39 specimens). Holotype, male: COSTA RICA. Est. Pitilla, 9 km S. Sta. Cecilia, P.N. Guanacaste, Prov. Guanacaste, 700m, May, 1994, C. Moraga, CRI 001 832764. Allotype, female: Prov. Guanacaste, Est. Pitilla, 9 km S Santa Cecilia, 700m, Oct. 1996, C. Moraga, CRI 002 500213. Paratypes. Guanacaste: ibid. allotype, 5 specimens; ibid. holotype, 1 specimen; ibid., Junio 1994, 3 specimens; ibid., Agosto 1993; Sector Santa María, 25 km NE de Liberia, 790 m, 9­27 Oct, 1996, D. Briceño, 6 specimens; 11­18 Nov, 1996, 2 specimens. Alajuela: Sector San Ramón de Dos Ríos, 1.5 Km NO Hda. Nueva Zelandia, 620m, 12­21 Julio 1996, F.A. Quesada, 14 specimens; 17­28 set 1995, 1 specimen; Puesto Quebradón, 300 m, Nov 1997, G. Rodríguez, trampas de intercepción, con agua de sal, Baykil y frutas en las tazas, 1 specimen; San Lorenzo, 600­620 m, 16­19 Septiembre 1996, F.A. Quesada, 1 specimen. Heredia: Est. Biológica La Selva, 21­VI­1998, C. Carleton & A. Tishechkin, 1 specimen; 50­150 m, 14­Mayo 1993, INBio­ OET, bosque secundario, 1 specimen.

Habitat. This species has been collected using traps baited with rotting meat or with flight interception traps inside tropical rain forest.

Geographical distribution. This new species of Trichillum occurs on both the Atlantic and Pacific slopes, along the bases of the volcanoes of the Guanacaste and Tilarán Cordilleras.

Chorological affinities. So far this is the northernmost distribution range known for a member of the genus Trichillum . This species will most probably be also found in the Atlantic rain forests of Nicaragua.

Taxonomic Relationships. The species belongs to the subgenus Eutrichillum , as defined by Martínez (1967). Based on external characteristics, the clypeo­genal suture, the punctation of the pronotum and the piliferous punctation and flatness of the elytral intervals, this new species seems to be related to T. boucomonti Arrow.

Etymology. From the Latin word meaning rainbow, a reference to the iridescent coloration of this species.

Figures

FIGURE 6. Dorsal habitus of Trichillum arcus Solís & Kohlmann, sp. nov. (holotype).