Dorcus brevis (Say, 1825)

Paulsen, M. J., 2010, Stag beetles of the genus Dorcus MacLeay in North America (Coleoptera, Lucanidae), ZooKeys 34 (34), pp. 199-207 : 200-202

Dorcus brevis and D. parallelus

The overall broader form of the body of D. brevis (Fig. 1) is often adequate to distinguish it from the relatively narrower D. parallelus (Fig. 2). However, the most useful and obvious external character for separating the North American species is the shape of the posterior pronotal angle. In D. brevis , the posterior angles are in close proximity to the elytral bases

Figures Ι–2. Dorsal habitus of major males. Ι Dorcus brevis (length 30mm) 2 Dorcus parallelus (length 26mm). Scale bar = 5mm.

(Fig. 3). In D. parallelus , the angles are distinctly removed from the base of the elytra (Fig. 4). The humeral angles of D. brevis are generally more strongly dentate and the humeri produced forward of the scutellum, while in D. parallelus the humerus is less strongly dentate and more or less in line with the scutellum. In addition, males of D. parallelus have a dense field of setae on the internal face of the metatibia (Fig. 5), but this patch is not present on males of D. brevis (Fig. 6). The clypeus is distinctly broader in males of D. parallelus .

In both species, the mandibles of major males have a single large dorsal tooth, but the dentition of the mandibles of minor males is clearly distinct. Even the smallest minor males of D. parallelus have mandibles that are of the same basic shape as major males, but they are simply reduced in size (Fig. 7). In contrast, minor males of D. brevis have two distinct internal teeth below the dorsal tooth and are abruptly curved internally (Fig. 8).

The form of the male genitalia is radically different in the two species. The flagellum of D. parallelus is longer than the entire length of the body and is weakly flared at the apex (Fig. 9). The flagellum of D. brevis is less than half as long, with a large lobe-like sac at the apex (Fig. 10). The genitalia of the European species, D. parallelipipedus , differs from either species in being more strongly expanded medially and in possessing a trilobed apex (Fig. 11).

3

Figures 3–4. Outline of body shape in females. 3 Dorcus brevis 4 Dorcus parallelus , arrow pointing to posterior pronotal angle distinctly removed from the base of the elytra.