Xanthopygus, Kraatz, 1857

Chatzimanolis, Stylianos, 2022, A revision of the genus Xanthopygus Kraatz (Staphylinidae: Xanthopygina), Zootaxa 5099 (2), pp. 151-178 : 176

Key to the species of Xanthopygus

1. Antennomere 4 without tomentose pubescence ( Figs. 18 , 39 ); mandibles more or less straight except tip ( Figs. 15 , 37 ); eyes as long as 1/4 length of head ( Figs. 15 , 37 ); head appearing flat ( Figs. 15 , 37 ); sternite 6 with two anterior transverse lines ( Fig. 17 )................................................................................................ 2

- Antennomere 4 with tomentose pubescence (Figs. 10, 26, 33, 43, 50); mandibles curved from apical half ( Figs. 1 – 2 , 7, 40, 47); eyes as long as 1/3-2/5 length of head (Figs. 7, 23, 30, 40, 47); head appearing convex (Figs. 7, 23, 30, 40, 47); sternite 6 with single anterior transverse line (Fig. 9)..................................................................... 3

2. Antennomere 3 clearly longer than 2 ( Fig. 18 ); pronotum microsculpture polygon shaped; tergite 6 sparsely punctate; tip of paramere emarginate ( Figs. 19, 21 ).............................................................. X. luctuosus

- Antennomere 3 subequal to 2 ( Fig. 39 ); pronotum microsculpture with transverse lines; tergite 6 densely punctate; no male specimens known............................................................................ X. oliveirae

3. Antennomere 4 longer than wide ( Fig 50 ); pronotum densely punctate, typically with three rows of punctures on each half beside median line ( Fig. 48 ); sternite 7 in males with porose structure ( Fig. 49 )........................ X. xanthopygus

- Antennomere 4 subquadrate (Figs. 10, 26, 33, 43); pronotum not densely punctate, typically with two or less rows of punctures on each half beside median line (Figs. 8, 24, 31, 41); sternite 7 in males without porose structure (Figs. 9, 25, 32, 42)..... 4

4. Head and pronotum with medium to large size punctures (Figs. 7–8, 40–41); pronotum with 1–2 dense rows of punctures on each half beside median line (Figs. 8, 41); abdominal segments 4–6 with iridescent overtones under strong light (Figs. 7, 40). ................................................................................................... 5

- Head and pronotum with small to medium size punctures ( Figs. 23–24 , 30–31 ); pronotum with one sparse row of punctures on each half beside median line ( Figs. 24 , 31 ); abdominal segments 4–6 not iridescent under strong light ( Figs. 23 , 30........ 6

5. Abdominal segment 7 completely orange (Figs. 7, 9); abdominal segment 6 with a distinct bright band of orange coloration posteriorly (Figs. 7, 9); aedeagus with median lobe lacking subapical tooth ( Fig. 12 ); paramere in lateral view much shorter than median lobe ( Figs. 11–12 )..................................................................... X. cognatus

- Abdominal segment 7 never completely orange, typically anterior half dark or light brown ( Figs. 40, 42 ); abdominal segment 6 without a distinct bright band of orange coloration posteriorly ( Figs. 40, 42 ); aedeagus with median lobe having a subapical tooth ( Fig. 45 ); paramere in lateral view slightly shorter than median lobe ( Figs. 44–45 )....................... X. pexus

6. Paramere apically emarginate ( Figs. 34, 36 ); known from Peru............................................ X. max

- Paramere apically rounded ( Figs. 27, 29 ); known from Colombia......................................... X. major

Figures

FIGURES 15–18. Xanthopygus luctuosus (Blanchard). 15. Habitus photograph. 16. Pronotum. 17. Sternites 6–8. 18. Antenna. Not to scale.

FIGURES 37–39. Xanthopygus oliveirae Lynch. 37. Habitus photograph. 38. Pronotum. 39. Antenna. The pronotum of this specimen is depressed dorsally (probably due to preservation). Not to scale.

FIGURES 1–6. Xanthopygus xanthopygus (Nordmann). 1. Dorsal view of left mandible, scale bar = 2.1 mm. 2. Dorsal view of the right mandible, scale bar = 2.1 mm. 3. Maxilla, scale bar = 1.0 mm. 4. Hypopharynx and labial palps, scale bar = 0.8 mm. 5. Prosternum, scale bar = 1.8 mm. 6. Meso- and metaventrite, scale bar = 2.6 mm.

FIGURES 19–21. Aedeagus of X. luctuosus (Blanchard). 19. Dorsal view. 20. Lateral view. 21. Detail of paramere, ventral view.

FIGURES 47–50. Xanthopygus xanthopygus (Nordmann). 47. Habitus photograph. 48. Pronotum. 49. Sternites 6–8. 50. Antenna. Not to scale.

FIGURES 23–26. Xanthopygus major (Bernhauer). 23. Habitus photograph. 24. Pronotum. 25. Sternites 6–8. 26. Antenna. Not to scale.

FIGURES 30–33. Xanthopygus max Blackwelder. 30. Habitus photograph. 31. Pronotum. 32. Sternites 6–8. 33. Antenna. Not to scale.

FIGURES 11–13. Aedeagus of X. cognatus Sharp. 11. Dorsal view. 12. Lateral view. 13. Detail of paramere, ventral view.

FIGURES 40–43. Xanthopygus pexus (Motschulsky). 40. Habitus photograph. 41. Pronotum. 42. Sternites 6–8. 43. Antenna. Not to scale.

FIGURES 44–46. Aedeagus of X. pexus (Motschulsky). 44. Dorsal view. 45. Lateral view. 46. Detail of paramere, ventral view.

FIGURES 34–36. Aedeagus of X. max Blackwelder. 34. Dorsal view. 35. Lateral view. 36. Detail of paramere, ventral view.

FIGURES 27–29. Aedeagus of X. major (Bernhauer). 27. Dorsal view. 28. Lateral view. 29. Detail of paramere, ventral view.