Key to Piezonemus species

1 Male: tarsomere I of protarsus and mesotarsus with distinct spur at apex in male (Figs 78–79). Female: pygidium flat, without any promontory (Fig. 83)......................................................... Piezonemus espoch sp. nov.

- Male: tarsomere I of protarsus and mesotarsus without distinct spur at apex in male, only tarsomere I of mesotarsus dilated at apex on inner side (Fig. 53). Female: pygidium with bifurcated promontory (Figs 70–72)............................ 2

2 Male: tarsomere I of mesotarsus shorter than others together (Fig. 53), pygidium elongate, ratio of the maximum length to maximum width 1.24 (Figs 46, 54). Female: pygidium with distinct promontory before apical edge, this projection high and deeply divided basally (Fig. 70). Eyes shorter (Figs 44, 50)...................................... Piezonemus durus

- Male: tarsomere I of mesotarsus distinctly longer than others combined (Fig. 69), pygidium obviously elongate, ratio of the maximum length to maximum width 1.36 (Fig. 66). Female: pygidium with distinct promontory before apical edge, but this projection not so high and not deeply divided basally. Eyes longer (Fig. 63)....................... Piezonemus lateralis

Notes on Piezonemus and confusion with some species of the genus Piesocorynus

During the study of Neotropical species of the tribe Piesocorynini in world collections, misidentifications between the similar genera Piezonemus and Piesocorynus were found, as well as confusion caused by abbreviated scientific names on determination labels. For specimens labelled as ‘ P. lateralis Jordan’, it is not clear whether Piezonemus lateralis Jordan, 1904 or Piesocorynus lateralis Jordan, 1906 is intended. Moreover, the two species, and the two genera, are somewhat similar and are confused in collections.

Furthermore, both specimens of the new species described here, Piezonemus espoch sp. nov., have been misidentified in the past. The holotype (male) was previously determined as Piezonemus lateralis (R. Frieser det. 1996), and the allotype (female) had been determined as Piesocorynus sp. (B.D. Valentine det. 2010).

In addition, one specimen determined by R. Frieser as Piezonemus lateralis (R. Frieser det. 1953) was found in his collection (now in ZSMC), which, however, belongs to the genus Piesocorynus, specifically to the species P. obliquus Frieser, 1978, which Robert Frieser described himself, but he did not include this specimen in the type series.

It follows from the above, that distinguishing the genera Piezonemus and Piesocorynus can be difficult. We help to resolve these inaccuracies by illustrating the type material of the relevant species. Therefore, we studied the holotype (male from Panama) and paratype (male from Guatemala) (both in BMNH) of Piesocorynus lateralis, and the holotype (male from Brazil, in ZSMC) and two paratypes (male and female from Brazil, MTDC) of Piesocorynus obliquus . The main distinguishing features of both species are:

Piesocorynus lateralis (Figs 90–95): disc of pronotum convex, simple, without bumps, uniform coloured (Figs 92, 95). Dorsal transverse carina of pronotum straight (Fig. 92). Elytra almost flat, with only faint pair of bumps in sub-basal part (Fig. 95). Size 5.5–5.8 mm. Distribution: Central America (Panama, Guatemala, Mexico).

Piesocorynus obliquus (Figs 96–100): disc of pronotum with one central and two lateral bumps, with narrow longitudinal contrasting yellow strip in central part (Figs 98, 100). Dorsal transverse carina of pronotum bisinuate (Fig. 98). Elytra with pair of distinct bumps in sub-basal part (Fig. 100). Size 2.5–4.0 mm. Distribution: South America (Brazil).