Canthidium margaritae Kohlmann & Solís, 2006

Kohlmann, Bert & Solís, Ángel, 2006, New species of dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae) from Mexico and Costa Rica, Zootaxa 1302, pp. 61-68 : 62-65

Canthidium margaritae Kohlmann & Solís sp. nov. ( Figs. 1–3 )

Diagnosis. This species is distinguished by the following combination of characters: body globose; head and pronotum uniformly and strongly punctate; frons swollen; frontoclypeal region with a small, smooth swelling medial to each eye; eye dorsally at posterior end of gena narrow, eight to ten facets wide, interocular distance separated by approximately 8–10 times maximal eye width; basal pronotal border not margined; elytra with eight striae, surface lightly shagreened, microsculpture coarser towards apex; hind wing brachypterous.

Description of Holotype. Male. Length: 4.5 mm, humeral width: 2.9 mm. Body form globose ( Fig. 1 ). Head and pronotum coppery­red, elytra dark brown ( Fig.1 ). Head and pronotum strongly punctate and devoid of setae.

Clypeus rugosely punctate, apex strongly bidentate, median emargination broadly Vshaped ( Fig. 2 a); eye dorsally at posterior end of gena narrow, eight to ten facets wide, eyes separated by approximately 8–10 times maximum eye width ( Fig. 2 a). Frons and vertex of head strongly punctate, frons swollen; two small, black, smooth swellings between eyes ( Fig. 2 a).

Pronotum on disc and posterior angles slightly shagreened; surface strongly and uniformly punctate; lateral fovea oval; posterior margin lacking elongated punctures or groove.

Elytral striae consisting of clear indented lines interrupted by fairly evenly spaced oval punctures (approximately the maximum length of one puncture); intervals shiny, finely punctate; surface shiny and slightly shagreened especially towards apex. Elytra globose; hindwing brachypterous ( Fig. 2 h).

Pygidium distinctly punctate, more coarsely so in basal half, surface shiny and slightly shagreened at base. Genitalia as in Fig. 2 g.

Protibia with three teeth on external border ( Fig. 2c ), inner apical margin of protibia produced into a rounded anterior projection and slightly bent downwards ( Fig. 2c ), apical spur with incurved apex ( Fig. 2c ). Pro­, meso­ and metafemora with ventral surface finely punctate and finely shagreened.

Allotype. Female. Length: 4.6 mm, humeral width: 3.1 mm. Differing from male in the following major characters: clypeus slightly more transversely rugose ( Fig. 2 b), apical spur not forming incurved apex and claw­bearing protarsus not as thick ( Fig. 2 d), pygidium broader and less heavily punctate ( Fig. 2 f), last abdominal segment broader, inner apex of protibia not forming a rounded lobe ( Fig. 2 d).

Variation. Elytral surface can range from completely shagreened to shagreened only on the apical third.

Material examined (8 specimens). Holotype male: MÉXICO. Estado de México. Sierra de Nanchititla, Palos Prietos, 28–29­julio­2005, Alt. 1750 m, coprotrampa, M. Castillo, A. y L. Delgado cols. Allotype female: ibidem. Paratypes: MÉXICO. Estado de México. Sierra de Nanchititla, 18–19­VIII­96, 1800 msnm, G. Nogueira col., (1 female); same data as holotype (4 males, 1 female).

Habitat. This species has been found in cloud forest mixed with oaks in elevations ranging from 1,750 to 1,800 m above sea level.

Geographical distribution. It is only known in the State of México in the Sierra de Nanchititla on the upper reaches of the Balsas river depression ( Fig. 3 ).

Chorological affinities. The known range of Canthidium margaritae is widely separated from that of a very similar species, C. riverai , which is distributed in the Manantlán (Jalisco State) and the Coacolmán (Michoacán state) mountain ranges at similar altitudes (960–2,000 m above sea level) and in cloud forests.

Taxonomic relationships. Canthidium margaritae is postulated to be the sister species of C. riverai . They are both globose in body shape and brachypterous, they also have a swollen frons, clearly punctate pronotum, shagreened elytra, evenly impressed striae, and they both inhabit cloud forests. This species pair apparently represents a vicariant speciation event between the Sierra Madre del Sur ( C. riverai ) and the Neovolcanic Axis ( C. margaritae ).

C. margaritae will key to C. riverai Kohlmann and Solís in couplet 12 in the Kohlmann and Solís (2006) key for the Canthidium of Mexico. The two species are very similiar, but C. margaritae can be easily separated from C. riverai by having bigger eyes (8–10 eye facets versus 2–3 eye facets), head and pronotal punctures less coarse, elytra less shagreened, a different metatibial form (internal apical angle projected like a tapering rectangle versus apically obliquely truncated), and differences in the form of the parameres (parameres taper evenly towards apex versus parameres with a small hump at apical two­thirds).

Etymology. We dedicate this species to Margarita Castillo, who has always supported Luis Leonardo Delgado in his entomological studies and also helped collect this new species. The name is derived from the latinized (margarita) Greek word μαργαρίτη, meaning a pearl.

Figures

FIGURE 1. Dorsal view of male Canthidium margaritae.

FIGURE 2. C. margaritae. a) Dorsal view of male head; b) dorsal view of female head; c) dorsal view of right male protibia; d) dorsal view of right female protibia; e) male pygidium; f) female pygidium; g) lateral view of aedeagus; h) dorsal view of brachypterous right wing of male.

FIGURE 3. Known distribution of Canthidium margaritae in Mexico.