Xanthoeme signaticornis
Creators: name: Santos-Silva, Antonio
name: Nascimento, Francisco Eriberto de L.
name: Botero, Juan Pablo
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Cerambycidae
Xanthoeme
Xanthoeme signaticornis

description: Xanthoeme signaticornis (Melzer, 1920)
Median lobe (Figure 88C 7–D7) substraight in lateral view; ventral lobe longer than dorsal lobe; ventral lobe with apex acuminate and dorsal lobe with rounded apex; basal apophysis longer than apical portion, basal region widened towards apex. Tegmen (Figure 88A 7–B7) about 0.87 length of median lobe, distal half curved in lateral view; distal region completely divided into parameres; parameres about 0.30 length of tegmen, divergent towards apex, with dense setae, both long and short, on apex; ring piece rounded, about 0.45 total length of tegmen, basal inner margin rounded, ′U̍-shaped; apical margin rounded.
On Oemina and Methioidina
This division of Oemini into Oemina and Methioidina is unsatisfactory and, in some cases, based on features not constant in the two subtribes. The size of the ommatidia is not a good option to support the division, especially because it is often not easy or even possible to know what should be considered fine or coarse. For example, according to Martins (1997) the ommatidia in Proeme Martins, 1978 are intermediate between Oemina and Methiodina, but the lower eye lobes are shorter than the genae. However, the lower eye lobes in some species of Proeme are longer than genae (eg Figure 47). Therefore, it is impossible to determine the correct subtribe. Likewise, the size of the lower eye lobes is variable; they may be coarsely faceted and not reach the inferior margin of the head (eg Figure 3). Finally, the extension of the metathoracic discrimen is too variable in both subtribes. For example, it can be present from base to apex in species of genera currently included in Methioidina, as Proeme (eg Figure 46), or incomplete, as in some species of genera currently included in Oemina (eg Figure 58).
Another difficulty with the delimitation of the subtribes, as mentioned, is related to the extremely variable ′diagnostic̍ characters which are usually based only on external morphology. Some studies suggest that the morphology of the genitalia can be useful for the classification of Cerambycidae, and especially suprageneric groups (eg Ehara 1954; Fragoso 1985a, 1985b).
In our study on the male genitalia of the subtribes (Figure 88), we did not find satisfactory features allowing the separation of Oemina and Methioidina. Although some specimens have acute projections (roof support), which are more sclerotised behind the parameres, it is possible to observe a gradation in both subtribes. For example, they are well developed in Oeme costata costata, less so in Proeme bucki, vestigial in Chromoeme angustissima and absent in Martinsia scabrosa and Xanthoeme signaticornis.
Based on these considerations, we consider Oemina and Methioidina to comprise a single taxon, especially because all features used to separate them are extremely variable in other tribes of Cerambycidae (eg Acanthocinini, Acanthoderini, and Desmiphorini).
description: Published as part of Santos-Silva, Antonio, Nascimento, Francisco Eriberto de L. & Botero, Juan Pablo, 2023, Taxonomy of Oemini (Coleoptera: Cerambycidae: Cerambycinae), with key to American genera, notes and new taxa, pp. 1917-1948 in Journal of Natural History 57 (41 - 44) on pages 1940-1941, DOI: 10.1080/00222933.2023.2272347, http://zenodo.org/record/10498716