Xenopygus Bernhauer

Caron, Edilson, De Castro, Jessica C., Da Silva, Maycon R. & Ribeiro-Costa, Cibele S., 2016, Phylogeny and revision of a colorful Neotropical genus of rove beetles: Xenopygus Bernhauer (Coleoptera: Staphylinidae), Zootaxa 4138 (1), pp. 59-82 : 63-65

Genus Xenopygus Bernhauer

Xenopygus Bernhauer, 1906: 196 (description, included species: X. analis ( Erichson, 1840) and X. bicolor (Laporte, 1835 )) ; Bernhauer & Schubert, 1914: 405 (world catalog, three species, X. cordovensis Bernhauer, 1910 added); Scheerpeltz, 1933: 1416 (world catalog, four species, X. peruvianus added (Solsky, 1872 )); Blackwelder, 1943: 451 (as subgenus of Philothalpus Kraatz, 1857 ); Blackwelder, 1944: 140 (Neotropical Checklist, as subgenus of Philothalpus , three included species); Blackwelder, 1952: 407 (as subgenus of Philothalpus ); Irmler, 1979: 31 (as a valid genus, three species, key to the species); Irmler, 1982: 206 (four species, X. peruvianus as species incerta, key to the species, X. confusus added); Herman, 2001 b: 3610 (world catalog, as a valid genus, five species). Type species: Philonthus analis Erichson, 1840 , subsequent designation by Blackwelder, 1943: 451.

Diagnosis. The genus Xenopygus can be distinguished from the more correlated genera of Xanthopygina as Dysanellus and Xanthopygus , by the combination of the following characters: a) antennomere V as wide as long to slightly wider ( Fig. 14); b) antennomere VII two times wider than long; c) internal margin of labial palp I slightly emarginate at middle ( Fig. 18); and d) superior line of pronotal hypomere developed, continuous on the anterior angles of pronotum ( Fig. 21, a).

Redescription. BL: 9.0–18.0 mm, BW: 3.1–3.4 mm. Dorsal surface of head and pronotum with metallic blue, green or dark brown color ( Figs. 2 –13); ventral surface of head to metaventrite, appendices and abdominal segments III–VI yellow to black; abdominal segments VII–X or VIII–X evidently lighter than the previous ones. Dorsum of head and pronotum with conspicuous microsculpture, elytra glabrous and abdomen with transverse microsculpture. Dorsum of head with dispersed setal punctuations, except for the head disc. Pronotum with setal punctuations forming a pair of longitudinal parallel lines in the median region and distributed in the lateral thirds (Fig. 5–7) or entirely distributed, not at the median longitudinal line (Figs. 11–13); anterolateral and posterolateral setae conspicuous ( Fig. 21, b, d). Elytra with setal punctuations evenly distributed, distance between punctuations equal to the diameter of each punctuation, elytral setae longer than the pronotal setae, posteriorly directed. Abdomen with setal punctuations widely distributed, dense or dispersed.

Head about as wide as long to two times wider than long. Eye larger than the lateral half of the head, and two to three times longer than the temples. Antennae reach apex of pronotum; antennomeres VI–X transverse and gradually increasing in width to the apex; antennomere VII two times wider than long; antennomere XI slightly longer than the width of its base. Labrum bilobate. Mandibles as long or longer than head, falciform and asymmetric in the internal margin; left mandible with two subcontiguous teeth and right mandible with only one tooth ( Figs. 15–16); prostheca developed; external margin of mandible with miniature setae in longitudinal sulcus. Maxilla with galea and lacinia densely setose; maxillar palpomere I is the shortest; II slightly longer than the III; IV about 1.5 times longer than the previous one ( Fig. 17). Mentum rectangular, three times wider than long. Labium with palpomeres I and II subequal in size; palpomere I with internal margin slightly emarginate at middle ( Fig. 18); palpomere II with internal margin protruding in the apical third; palpomere III slightly longer than the previous one and truncate in the apex ( Fig. 18). Postmandibular ridge complete, starting from the ocular seta ( Fig. 20, b, c); or infraorbital ridge not complete, reaching half the length of gena; postgenal and ventral basal ridge conspicuous ( Figs. 19, 20). Width of neck greater than half the width of head. Pronotum longer than wide, its apical third widest; basal margin widely curved and apical margin truncate; anterolateral angles obtusely rounded, curved ventrally; surface of pronotum slightly flat; hypomere expanded; superior and inferior marginal lines separated in all their length ( Fig. 21); superior line continuous with anterior margin; postcoxal process translucent ( Fig. 21). Scutellum well developed, triangular, almost a third of elytra’s length. Elytra longer than wide, longer and slightly wider than pronotum; apical margin emarginated at middle. Posterior wings totally developed. Mesoventrite process with apex slightly rounded to truncate; mesocoxa non-contiguous ( Fig. 22); mesocoxal cavities tightly emarginate posteriorly. Legs with straight tibia and spines in the external margin; tarsal formula 5 - 5 - 5; protarsomeres I–IV widened. Tergites III–IV or III–V with arched carina; segments III–VII with two pairs of paratergites, in which III–VI with paratergites equal in length and tergite VII with basal paratergite with half length of the apical ( Fig. 26); sternite VII with apical margin slightly emarginate at middle and in some species with evident porous structure at middle on male ( Figs. 23 a, 30–32).

Male's terminalia. Tergite VIII with posterior margin subtruncate, without paratergites; sternite VIII of male with apical margin slightly to tightly emarginate at middle ( Figs. 23 b, 33–38); tergite IX with a pair of wide plates totally separated by tergite X, each densely pubescent in the apical two thirds ( Fig. 27); sternite IX of male in the apical two thirds sparsely pubescent, posterior margin deeply medially emarginate ( Fig. 28); tergite X subtrapezoidal, sparsely pubescent in the apical half, apex weakly sclerotized and posterior margin emarginate ( Fig. 27). Aedeagus slightly curved ventrally in lateral view; apex of median lobe with small teeth in hook shape in ventral surface (Figs. 42 –44, 51– 53). Parameres fused in a single plate, reaching or exceeding the median lobe apex; apical two thirds with peg setae in dorsal surface ( Figs. 24 –25, 45–47, 54– 56).

Female's terminalia. Similar to male, except sternite VIII with apical margin subtruncate; sternite IX with ovipositor constituted by a pair of hemisternites, each hemisternite apically with conspicuous coxites and styles ( Fig. 29). Spermatheca not found.

Geographical record. Xenopygus is a typically Neotropical genus, based on the endemism areas proposal by Morrone (2014). It has wide distribution and has been recorded in Mexico, Belize, Guatemala, Nicaragua, Costa Rica, Panama, Colombia, Venezuela, Trinidad and Tobago, Guyana, French Guiana, Ecuador, Peru, Bolivia, Brazil, Paraguay, Argentina and Hawaii Pacific Islands (probably a synanthropic introduction) ( Figs. 57–59).

Biological notes. Species of this genus were found preying on fruitflies ( Diptera : Tephritidae ) ( Baker et al. 1944). There are occurrence records of the species associated with tree bark, fungi, decomposing fruits and carcasses. Furthermore, adults have been collected with flight interception traps or with pitfall baited traps.