Dichotomius boreus

Chamorro, William, Lopera-Toro, Alejandro & Rossini, Michele, 2021, A new species and distribution records of Dichotomius Hope, 1838 (Coleoptera Scarabaeidae: Scarabaeinae) in Colombia, Zootaxa 4942 (2), pp. 193-206 : 202-203

Key to species of the Dichotomius boreus species group

(Modified from Luederwaldt 1929; Vulcano & Pereira 1967; Sarmiento-Garcés & Amat-García 2014)

1 Pronotum with central lobes conical and directed forward or outward ( Figs. 3 A-E, 4C).............................. 2

- Pronotum with central lobes squared or almost squared, never conical ( Figs. 1 A-C, 2A-B)........................... 5

2 Anterior cephalic carina strongly elevated, with distinct, well-separated tubercles on extremities (width more than 3 mm) ( Figs. 3A, C).............................................................................................. 3

- Anterior cephalic carina concave (weakly elevated) with small and closer apices (less than 3 mm width) ( Figs. 1D, 2C, 3D, 4C)................................................................................................ 4

3 Anterior cephalic carina with horn-shaped tubercles, curved backward at apex. Frontal transverse carina with a small horn, with rounded apex and located between the eyes ( Fig. 3C)..................... Dichotomius carinatus ( Luederwaldt, 1925)

- Anterior cephalic carina with small conical tubercles and rounded apexes. Frontal transverse carina with tubercle with rounded apex located between the eyes ( Figs. 3 A–B).................................. Dichotomius telamon ( Harold, 1869)

4 Frontoclypeal carina trituberculate, the central tubercle slightly higher (this character tic may not be easily visible in damaged or minor specimens). Anterior region of pronotum almost vertical above head, superior region with two conical lobes directed forward; lateral declivity of pronotum with a small, acute carina-like protuberance ( Figs. 3 D–-E, 4A–B)..................................................................................... Dichotomius podalirius ( Felsche, 1901)

- Frontoclypeal carina trituberculate, central tubercle higher and positioned forward (in major specimens looks like small tubercle). Anterior region of the pronotum almost vertical above the head, superior region with two large conical lobes directed outward; lateral declivity of the pronotum with poorly-developed protuberance ( Fig. 4C)......................................................................................... Dichotomius prietoi Martínez & Martínez, 1982

5 Clypeal carina of male asymmetrical, right portion atrophied. Clypeal carina of female set at mid distance from anterior clypeal edge and tubercle on vertex. Pronotal lobes of large individuals almost subquadrate, apex transversally truncate, strongly emarginate in the male and weakly so in the female ( Figs. 2 A–E)................... Dichotomius boreus ( Olivier, 1789)

- Clypeal carina of male symmetrical, lateral tubercles equally developed. Clypeal carina of female closer to anterior clypeal edge than tubercle on vertex. Pronotal lobes of large individuals squared, outer edges normally with a projection rounded at the apex ( Figs. 1 A–F)........................... Dichotomius quadrilobatus Chamorro, Lopera, & Rossini , new species