Pachystilicus Casey, 1905

Żyła, Dagmara, Tokareva, Alexandra & Koszela, Katarzyna, 2022, Phylogenetic position of genera Acrostilicus Hubbard and Pachystilicus Casey (Staphylinidae, Paederinae) and their redescription, European Journal of Taxonomy 819 (1), pp. 1-22 : 10-12

Genus Pachystilicus Casey, 1905

Figs 3–4

Pachystilicus Casey, 1905: 226 (original description), 228 (comparison with Megastilicus ).

Pachystilicus – Blackwelder 1939: 107; 1952: 285 (notes). — Moore & Legner 1979: 11 (key), 111 (description). — Newton et al. 2001: 327 (characters in key), 387 (comment on taxonomic status).

Type species

Pachystilicus quadriceps ( LeConte, 1880) .

Diagnosis

The genus can be recognised based on the following combination of features: body robust (usually slender in Rugilus ), covered with fine, dense, golden setae (absent in Acrostilicus , Eustilicus Sharp, 1886 and Megastilicus Casey, 1889 ); antennal tomentose pubescence starting from antennomere 4; paired teeth on labrum (single in Acrostilicus ); the base of head broadly emarginate, punctation of head clearly denser and coarser than that of pronotum, head without dense ground sculpture (often present in Rugilus ); absence of scutellar ridges of mesoscutellum (one or two present in other North American Stilicina ).

Redescription

HABITUS. Medium sized, robust, covered with fine golden setae, integument densely punctured. Head more densely punctured than pronotum, without short and stout bristles.

COLOURATION. Dark brown; head darker, legs and antennae reddish brown.

HEAD. Trapezoidal, widest in middle, wider and longer than pronotum, temples straight, hind angles rounded, posterior margin emarginate (sinuate), disc rugose, punctation dense, rather fine, interstices reduced to narrow ridges, without microsculpture. Eyes large, approximately ⅓ of head length, slightly protruding, eyes with setae between ommatidia. Antenna 11-segmented, somewhat incrassate; antennomeres 4–11 with tomentose pubescence. Clypeal margin straight. Labrum transverse, twice as wide as long or wider, expanded, covering mandibles when closed, highly sclerotised in posterior part, less sclerotised in anterior part, anterior margin arcuate, with two long median teeth and four long setae (two per each side of teeth), incision between teeth rounded. Mandible without prostheca; maxillary palpus 4-segmented; maxillary palpomere 1 small; maxillary palpomere 2 longer than wide, widest near apex, with only few setae, with denser pubescence than maxillary palpomere 1; maxillary palpomere 3 almost twice as long as maxillary palpomere 2 and wider than it, slightly expanded, widest near apex, vase-like; maxillary palpomere 4 small, acicular, glossy and thin, shorter than wide, narrower and shorter than width of maxillary palpomere 3. Labial palpus 3-segmented, labial palpomere 1 slightly longer than wide, widest near apex; labial palpomere 2 about as wide as labial palpomere 1, longer than it, widest near apex; labial palpomere 3 shorter and distinctly narrower than labial palpomere 2, cylindrical. Mentum transverse, rectangular. Ligula entire, not bilobed, dorsal plate without setae. Gular sutures fully fused, not reaching posterior margin of head. Neck narrow, less than 1/5 of head width.

THORAX. Pronotum wider than long, rhomboid, with anterior angles obtuse, narrower in anterior and posterior part, widest in middle, disk finely densely punctured, midline less punctured. Long black seta on each side of pronotum, in apical portion of widest part; shorter black seta in posterior portion of widest part. Superior marginal line deflexed, not meeting with inferior line. Basisternum of prosternum without macrosetae or microsculpture, but surface wrinkled, longitudinal carina present. Furcasternum of prosternum longer than ½ of basisternum length, reaching farther than tip of postcoxal process, triangular, acute, with sharp longitudinal carina and transversal carina. Hypomeron not delimited from pronotal disc by carina. Furcasternum of mesosternum with longitudinal carina, short, reaching less than ⅓ of distance between coxae, rectangular. Elytra quadrate, longer and wider than pronotum, with row of setae on edge of posterior margin, without epipleural ridge; humeral angle indistinct, rounded; surface glossy, interstices without microsculpture. Scutellum without ridges, integument reticulate, anterior margin rounded. Hind wing fully developed, with MP3 vein present. Legs, as rest of body, covered with shiny gold setae. Trochantins large, quadrate. Middle coxa contiguous, ridge below coxal rests present. Tibiae without spines or long bristles on outer edge. Protibia with two fully developed, longitudinally placed, comb-like rows of setae, and three associated macrosetae. Tarsi 5-segmented, stout, with one pair of empodial setae on each tarsus, equal to or slightly shorter than claws. Protarsus narrowly dilated, protarsomere 1 slightly longer than protarsomere 5, protarsomeres 2–4 decreasing in length, protarsomeres 1–4 narrower or equal to meso- and metatarsomeres 1–4, with dense pale adhesive setae on ventral side, protarsomere 4 not bilobed. Mesotarsus with mesotarsomere 1 longer than mesotarsomere 2, mesotarsomere 4 similar to preceding one. Metatarsus with metatarsomere 1 longer than metatarsomere 2, metatarsomere 4 similar to preceding one, metatarsomere 5 equal to metatarsomere 1, longer than metatarsomere 4, but shorter than metatarsomeres 2–4 combined.

ABDOMEN. Finely pubescent, with fine and dense punctation, wider than elytra, widest at tergite V. Both ventral and dorsal sides with golden setae mixed with numerous longer black ones. Tergites III–VI impressed at base. Tergites III–VII with pair of paratergites on each side. Tergite VIII with posterior margin rounded. Sternite III without keel between coxae. Female: posterior margin of sternum VIII straight. Male: sternum VIII with moderately deep and broad median emargination of posterior margin; sides of emargination rounded ( Figs 3B , 4C ).

AEDEAGUS. With parameres reduced and fused to median lobe; ventral process stout, apically broadly truncate, slightly longer than uneverted internal sac; in parameral view ventral process bent and with apex acute ( Figs 3C–D , 4D–E ).

Figures

Fig. 3. Pachystilicus quadriceps (LeConte, 1880), habitus photograph and drawings of the apical abdominal sternite and genital structures. A. Habitus, lectotype, ♂ (MCZ). B. Male sternite VIII. C. Aedeagus, parameral view. D. Aedeagus, lateral view. Scale bar = 0.5 mm.

Fig. 4. Pachystilicus hanhami (Wickham, 1898), habitus photographs and drawings of the apical abdominal sternite and genital structures. A. Habitus, holotype, ♂ (NMNH). B. Habitus, additional male specimen with darker colouration (NMNH). C. Male sternite VIII. D. Aedeagus, parameral view. E. Aedeagus, lateral view. Scale bars = 0.5 mm.