Philydrodes Bernhauer, 1929

Shavrin, Alexey V., 2017, Five new species of the genus Philydrodes Bernhauer, 1929 from China (Coleoptera: Staphylinidae: Omaliinae: Anthophagini), Zootaxa 4231 (2), pp. 169-186 : 170-172

Philydrodes Bernhauer, 1929

Philydrodes Bernhauer, 1929: 179

Philydrodes: Nakane & Sawada 1956: 179 ; Watanabe 1990: 61, 265, 309

Description. Body more or less flattened, shiny, with coriaceous microsculpture on head and pronotum; length 3.0–8.0 mm. Coloration varying from reddish brown to black, sometimes with paler pronotum and/or elytra. Punctation variable: small and sometimes indistinct on head, deeper and denser on pronotum and elytra. Head subtrapezoidal (Fig. 423 in Watanabe 1990) to subquadrate ( Fig. 11 ), with postocular parts significantly widened in male or not widened in both sexes, with wide and deep trapezoidal interocellar impression and moderately deep furrows (grooves) beginning above ocelli and obliquely extending posteriad; gular sutures united or slightly separated at narrowest point ( Fig. 11 ). Eyes convex, small to medium-sized. Ocelli moderately large, very distinct. Labrum transverse ( Fig. 6 ). Mandibles slender, each mandible with two elongated teeth on inner margin, right mandible with additional distinct smoothed tooth ( Fig. 7 ). Labial palpomeres distinctly longer than their width ( Fig. 9 ). Maxillae narrow, with elongated galea and maxillary palpomeres; apical maxillary palpomere narrow, indistinctly widened in median part and distinctly shorter than preceeding palpomere. Antennae reaching apical third or fourth of elytra, with very elongated antennomeres. Pronotum convex, moderately small, distinctly transverse or narrow, subequal to head; prothorax with elongated intercoxal process and wide triangular mesosternal processes (Fig. 424 in Watanabe 1990) or near basal portion ( Fig. 12 ). Mesothorax elongated, with acute intercoxal process reaching posterior margin of mesocoxae ( Fig. 14 ). Scutellum large, with tongue-shaped apical portion ( Fig. 13 ). Metathorax subtrapezoidal, with moderately deep intercoxal cavities and angular intercoxal process ( Fig. 14 ). Metendosternite with elongated basal stalk and furcal arms, as in Fig. 16 . Elytra moderately short, distinctly dilated posteriad. Hind wings fully developed. Legs slender, with transverse procoxae ( Fig. 18 ) and metacoxae ( Fig. 20 ) and suboval mesocoxae ( Fig. 19 ); protarsi of males with dilated tarsomeres ( Fig. 21 ); 4th segment of protarsi concaved apically ( Fig. 21 ), 4th segments of meso- ( Fig. 22 ) and metatarsi ( Fig. 23 ) with elongated membranous apex lobed beneath; apical tarsal segments distinctly longer than three preceeding segments. Abdomen with two moderately wide transverse tomentose spots on abdominal tergite IV and with palisade fridge on apical margin of abdominal tergite VII. Aedeagus with large or small phallobase; parameres short and moderately wide, or long and narrow. Female genital segment with moderately wide and long gonocoxites, with very small transverse styli ( Fig. 29 ).

Notes. Watanabe (1990) divided genus into two subgenera: nominative and Minyphilydrodes . The species from the nominative subgenus characterized by the larger body length (4.5–8.0 mm), by the distinctly pronounced dimorphism in males having considerably widened postocular parts of head (see Fig. 423 in Watanabe 1990), by the slender penultimate segment of maxillary palpi three times longer than broad and by the more flattened pronotum with clearly visible lateral margins when viewed dorsally. Minyphilydrodes contains species with the smaller body length (3.0– 4.3 mm), without modified postocular parts of head ( Fig. 11 ), with penultimate segment of maxillary palpi distinctly widened apicad and less than three times longer than broad, with more convex pronotum and lateral margins of pronotum indistinctly visible from the dorsal side. The Chinese species have some sufficient characters similar to that of Minyphilydrodes : proportions of maxillary palpi, not widened postocular parts of head (head of males is slightly wider than pronotum and distinctly wider in females). At the same time, the body length of Chinese species varies from 3.5 to 5.7 mm, the pronotum is distinctly smaller, narrower and less transverse, with clearly visible lateral margins if viewed dorsally, the prothorax with triangular mesosternal processes shifted to the basal portion (compare Fig. 424 in Watanabe 1990 and Fig. 12 ), and aedeagus with small to large phallobase and long parameres. Three species ( Ph. tibetanus sp.n., Ph. tridentatus sp.n. and Ph. wrasei sp.n.) have latero-apical and apical projections of the median lobe of the aedeagus similar to that of Ph. (s.str.) tsurugisanus Watanabe, 1990 from Shikoku (see Fig. 442 in Watanabe 1990). Thus, the described species from China were tentatively placed by me within Minyphilydrodes as a group of related species, and real phylogenetic relations between taxa of Philydrodes must be verified in the future after the detailed examination of the internal structure of the aedeagi of Japanese species.

Differential diagnosis. Based on the shape of mandibles, the presence and arrangment of two teeth on the inner margin, the short apical segment of the maxillary palp distinctly smaller and narrower than preceeding segment, by the densely pubescent antennes, and by the general shape of the aedeagus, Philydrodes is similar to Hygrodromicus Tronquet, 1981 , Liophilydrodes Nakane, 1983 and Microedus LeConte, 1874 , and, by the character of microsculpture of the head and pronotum and by the very narrow apical maxillary palpomere it is more similar to the latter two genera. It can be distinguished from Microedus and Liophylidrodes by the slightly widened medial part of the apical maxillary palpomere (compared to genera with apical maxillary palpomere narrower, parallelsided and awl-shaped, and with wider preapical palpomere), and by the less transverse pronotum. From Hygrodromicus it differs by the narrower body and by the distinctly wider preapical maxillar palpomere, as well as by the well developed ocelli (ocelli of some species of Hygrodromicus can be reduced). From all these genera Philydrodes differs by the larger head, sometimes distinctly wider than pronotum as in Brathinus LeConte, 1852 and Anthophagus Gravenhorst, 1802 , with significantly or insignificantly pronounced sexual dimorphism (for details see above), by the more slender mandibles with narrow basal part, by the narrower maxillary palpi, and labial palpomeres. The shape of phallobase of some Chinese species of Philydrodes are similar to that of Hygrodromicus ( Zerche 1992) which also can be 90° rotated inside the abdomen in lateral position (if viewed dorsally). In habitus, Philydrodes is related to the Holarctic group of genera of the tribe Anthophagini , all taxa of which have deep interocellar impressions between eyes. Zerche (1992, 2003) named these genera as “ Hygrogeus - Gruppe” and included several palaearctic genera ( Altaiodromicus Zerche, 1992 , Geodromicus Redtenbacher, 1857 , Hygrodromicus Tronquet, 1981 , Hygrogeus Mulsant and Rey, 1880 , Liophilydrodes Nakane, 1983 , Paratrichodromeus Zerche, 1992 , Trichodromeus Luze, 1903 ), and to which Microedus , with several Nearctic ( Hatch 1957) and Palaearctic ( Newton et al., 2000) species, should be referred.

Bionomics. The detailed bionomics data for the most Japanese Philydrodes are unknown: Watanabe (1990) provided only a comment that these species can be “[...] found in damp dead leaves accumulated along mountain streams or under stones at the stream side”. Two species described from the Eastern Shikoku were collected in high altitudes near streams in wet litter ( Watanabe 2012). All Chinese species have been collected in high mountain habitats with elevations between 1550 m a.s.l. to 4200 m a.s.l. from wet mosses, debris, leaf litter, under stones etc. near rivers and small streams.

Figures

FIGURES 11 – 23. Body parts of Philydrodes tridentatus (paratype, male): 11 — ventral aspect of head, 12 — ventral aspect of prothorax, 13 — scutellum (dorsal view), 14 — ventral aspect of mesothorax, 15 — ventral aspect of metathorax, 16 — metendosternite (ventral view), 17 — ventral aspect of elytron, 18 — fore leg (anterior view), 19 — middle leg (anterior view), 20 — hind leg (anterior view), 21 — protarsus (dorsal view), 22 — mesotarsus (dorsal view), 23 — metatarsus (dorsal view). Scale bars 0.1 mm.

FIGURES 6 – 10. Mouthparts (dorsal view) of Philydrodes tridentatus: 6 — labrum, 7 — mandibles (left and right), 8 — maxilla (right), 9 — labium, 10 — submentum. Scale bars 0.1 mm.

FIGURES 24 – 29. Abdominal segments of Philydrodes tridentatus: 24 — male tergite VIII, 25 — male sternite VIII, 26 — male genital segment, 27 — female tergite VIII, 28 — female sternite VIII, 29 — female genital segment. Scale bars 0.1 mm.