Xanthopygus Kraatz, 1857 sensu Chatzimanolis 2021

Chatzimanolis, Stylianos, 2022, A revision of the genus Xanthopygus Kraatz (Staphylinidae: Xanthopygina), Zootaxa 5099 (2), pp. 151-178 : 153-154

Xanthopygus Kraatz, 1857 sensu Chatzimanolis 2021

( Figs. 1–55 )

Xanthopygus Kraatz, 1857: 539 .

Type species: Staphylinus xanthopygus Nordmann, 1837 , fixed by absolute tautonymy ( Herman 2001).

Lampropygus Sharp. 1884: 346 . Synonym of Xanthopygus ; Blackwelder 1943. Type species: Staphylinus xanthopygus Nordmann, 1837 , fixed by subsequent designation by Lucas 1920: 361.

Heteropygus Bernhauer, 1906: 195 . Synonym of Xanthopygus ; Blackwelder 1943. Types species: Blackwelder (1943) listed giganteus as the type of Heteropygus as being monotypic; however, Bernhauer (1906) included two species ( giganteus and oliveirae ) in his definition of Heteropygus , therefore the statement by Blackwelder is invalid. Lampropygus giganteus Bernhauer is here designated as the type species of Heteropygus .

Type species: Staphylinus xanthopygus Nordmann, 1837 , fixed by absolute tautonymy ( Herman 2001).

Species included: cognatus , luctuosus , major , max , oliveirae , pexus and xanthopygus .

Diagnosis: Modified from Chatzimanolis (2021). Xanthopygus can be distinguished from all other genera in Xanthopygina based on the combination of the following characteristics: head wider than long and rectangular in shape; head wider than pronotum; antennomeres 7–10 transverse; left mandible with two teeth separated by deep emargination; labial palpomere 3 parallel-sided, not securiform; eye size small (less than 2/5 length of head); superior marginal line of pronotal hypomeron not continuing to anterior margin; superior and inferior marginal line of pronotal hypomeron produce anterolateral angles not parallel to one other; postcoxal process present; elytra coloration black (except with blue metallic overtones in Xa. xanthopygus ); dorsal 1/3 of metepisterstum without punctures throughout its length; with more than four spines on the posterior surface of metacoxae (except in X. xanthopygus , four); tergites 3–5 with arch-like carina; and sternite 7 in males with emargination at posterior margin. For a list of characters that distinguish Xanthopygus from Photinopygus , see Chatzimanolis (2021).

Description. Habitus as in Figs. 7, 15, 23, 30, 37, 40, 47. Body medium-sized to large, forebody 6.0– 17.3 mm, without long bristle-like setae. Coloration dark brown to black except posterior abdominal segments orange. Head shape rectangular; head length in comparison to pronotum shorter (except X. luctuosus ). Eye size small, less than 2/5 length of head. Postclypeus, in comparison to frons, not deflexed; anterior margin more or less straight. Middle of epicranium impunctate but with microsculpture. Postmandibular ridge laterally; with deep punctures demarcating raised postmandibular ridge present. Gular sutures not joined before neck, extended close to each other at base of head capsule. Posterior margin of head more or less at same level with neck border. Nuchal ridge incomplete dorsally. Neck disc without or with sparse punctures.

Antennae (Figs. 10, 18, 26, 33, 39, 43, 50) with relative width of antennomere 1 equal or slightly wider than 2. Third antennomere 2.5 times as long as wide or less; antennomere 4 with tomentose pubescence absent ( X. luctuosus , X. oliveirae ) or present (other species); antennomeres 4–10 cylindrical in shape; antennomeres 5–10 without club; antennomere 5 subquadrate; antennomeres 7–10 symmetrical, transverse; antennomere 6 with curved, distinctly longer and thicker subapical setae than other macrosetae, forming a circlet; antennomere 11 in males subequal to 10.

Mouthparts with labrum having broadly U-shaped emargination, lobes strongly separated. Mandibles ( Figs. 1–2 ) with relative length typical (i.e., closed mandible not extending beyond lateral margin of head); without asymmetrical torsion. Mandibles in dorsal view curved from apical half in most species except more or less straight (except tip) in X. luctuosus and X. oliveirae ; in lateral aspect straight; left mandible with two teeth separated by deep emargination; right mandible with one tooth. Maxilla ( Fig. 3 ) with galea much shorter than palpus; maxillary palpus with palpomere 3 shorter than 2; palpomere 4 longer than 3; palpomere 4 not dilated (parallel-sided). Labial palpus ( Fig. 4 ) with palpomere 3 widest before apex; palpomere 3 without long dense setae on entire lateral sides. Ligula small, entire. Mentum with alpha seta present; hypostomal cavity present; moderately delimited.

Pronotum with shape of lateral margins in dorsal view posteriad of midpoint straight to sinuate; anterior angles in dorsal view not strongly acuminate and produced laterad. Pronotum near anterolateral angles without raised impunctate spots; anterolateral corners with punctation; disc of pronotum with punctation beyond midlength; punctation varies but with transverse lines of microsculpture; without coarse punctures impressed in flange at posterior angle of pronotum. Hypomeron with superior marginal line not continuous to anterior margin; superior marginal line without distinct deflection under anterior angles in ventral view; inferior marginal line of hypomeron continued as separate entity beyond anterior pronotal angles and curving around them. Superior and inferior marginal lines produce anterolateral angles not parallel to one other (see figs. 2A–B in Chatzimanolis 2021). Postcoxal process present. Basisternum ( Fig. 5 ) slightly longer than furcasternum; basisternum with pair of macrosetae, situated far from anterior margin of prosternum.

Elytra well developed, longer than pronotum and together, not strongly transverse; hind wings present; hind wing venation with veins CuA and MP4 fused in one vein. Elytra setae not reduced, easily seen at low magnification; without patches of white setae. Elytra without contiguous polygon-shaped meshed microsculpture. Mesoscutelum with dense cluster of punctures medially. Mesoventrite ( Fig. 6 ) with apex of intercoxal process being broad and either rounded or pointed. Metepisternum with dorsal 1/3 without punctures throughout its length.

Legs 5-5-5; profemora without lateroventral apical spines; protarsi with modified pale (adhesive) setae ventrally; protarsi with tarsomeres 1–4 dorsoventrally flattened. Mesocoxae strongly separated, intercoxal area on approximately same plane as both meso and metaventrital processes. Metacoxae without coxal shield; with more than four spines on posterior surface (except X. xanthopygus , less than four). Metatibia without thick and long apical spurs but smaller spurs present; with spines. Meso/metatarsi with symmetrically lobed tarsomeres 1–4; tarsomeres 3–5 of metatarsi with chaetotaxy developed only at margins of dorsal surface; dorsal surface of tarsomeres glabrous along midline. Pretarsal claws with empodial setae.

Abdomen with lateral sides in dorsal view more or less parallel-sided; with protergal glands having well-developed acetabula. Anterior basal transverse carina on tergites 3 and 4 without pair of accessory ridges; tergite 3 without posterior basal transverse carina; tergites 3–5 with curved carina (arch-like) on disc; tergite 5 without pair of accessory ridges on anterior basal transverse carina; center of tergite 5 with punctation; posterior half of tergite 5 in lateral view not appearing bulging. Sternite 3 with straight to arcuate basal transverse carina medially; basal transverse carina laterally not sinuate. Sternite 4 without basal transverse carina medially. Sternite 5 with dense, meshed microsculpture anterolaterally, appearing different in texture to posterior portion. Males with secondary sexual structures (medial emargination) present on sternites 7 and 8; without porose structure (except X. xanthopygus ). Aedeagus with long median lobe and single paramere; paramere with sensory peg setae; median lobe with single subapical tooth (except in X. cognatus and X. xanthopygus , no tooth), without apical tooth, carina or paired apex. Spermatheca not sclerotized.

Figures

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

FIGURE 14. Distribution map of X. cognatus Sharp (squares) and X. pexus (Motschulsky) (circles).

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

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

FIGURE 22. Distribution map of X. luctuosus (Blanchard) (white squares), X. major (Bernhauer) (star), X. max Blackwelder (black squares) and X. oliveirae Lynch (circle).

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

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

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

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

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

FIGURES 51–53. Aedeagus of X. xanthopygus (Nordmann). 51. Dorsal view. 52. Lateral view. 53. Detail of paramere, ventral view.

FIGURE 54. Late instar larva of X. xanthopygus (Nordmann).

FIGURE 55. Distribution map of X. xanthopygus (Nordmann). The dubious record from Bolivia is not shown here.