Philonthus sericans ( Gravenhorst, 1802 )

Chani-Posse, Mariana, 2010, Revision of the southern South American species of Philonthus Stephens (Coleoptera: Staphylinidae) 2595, Zootaxa 2595, pp. 1-70 : 53-57

Philonthus sericans ( Gravenhorst, 1802)

( Figs. 128–131, 150)

Staphylinus sericans Gravenhorst, 1802: 171 . For complete references see Herman 2001b.

Diagnosis. Philonthus sericans may be identified by the head wider than long, the distance separating medial interocular punctures on frons about twice as large as distance separating medial punctures from lateral punctures, the antennal segments 4 and 5 elongate, the last segment of labial palpi 2 times as long as the second, and the tergum 10 with two apical setae in both sexes. It differs from other southern South American species of Philonthus by the dorsal rows on pronotum each with six punctures and the shape of aedeagus.

Redescription. Length of the body 5.5–6.2 mm. Coloration. Head piceous- black; thorax brunneous to piceous-brunneous, elytra castaneous-brunneous to castaneous-piceous with apical margins testaceo brunneus to brunneus or uniformly coloured (brunneous to testaceo-brunneus); abdominal segments piceous-brunneous with apical margins paler; antennae castaneous-piceous to castaneous-brunneous, palpi and legs brunneous.

Head moderately to distinctly wider than long (HW/HL= 1.5–1.2) and at basal third as wide as distal third in both sexes, about as wide as to slightly wider than pronotum (HW/PW= 1.14–0.96); dorsal surface coarsely and moderately punctate, with three to four postocular punctures and three to four epicranial punctures; distance separating medial interocular punctures on frons about twice as large as distance separating medial punctures from lateral punctures; infraorbital ridge present, extending not far beyond postgenal ridge. Eyes about as long as to slightly longer than temples (EL/TL= 1.14–1.02) seen from above. Antennae with segment 1 as long as segments 2 and 3 combined, segments 2 and 3 subequal in length, segments 4–6 elongate, 7–8 quadrate, 9–10 transverse. Maxillary palpus with segment 2 not swollen, no more than twice as long as its maximum width; last segment fusiform, about twice longer than segment 3. Submentum about 1.5 times as long as mentum. Labial palpus with last segment twice as long as preceding segment. Neck about 0.5 times as wide as head at widest point (NW/HW= 0.6–0.5).

Pronotum moderately longer than wide (PW/PL= 0.85), distinctly narrowed anteriad; dorsal surface of pronotum with two rows of punctures, each with six punctures. Hypomeron not visible in lateral view. Basisternum with medial longitudinal carina moderately developed, bulbous. Metasternum with circummesocoxal ridge broadly rounded medially. Elytra at sides moderately to distinctly longer than pronotum at midline (EtL/PL=1.4–1.2), distinctly longer than elytra along suture (EtL/Etl= 1.8–1.6); transverse distance between punctures about as large as to distinctly smaller than diameters of punctures. Both front and middle tarsi as long as front and middle tibiae; first segment of hind tarsus moderately longer than segments 2 and 3 combined, and about as long as last segment (S1/S5= 1.15–1.00). Abdominal terga distinctly punctuate at basal area, distance separating punctures distinctly smaller than diameters of punctures; terga 2 and 3 with elevated area between basal lines punctuate, posterior basal line straight medially. Male sternum 7 with apical margin slightly notched at middle. Tergum 8 in both sexes with posterior margin arcuate.

Male genitalia. Sternum 8 deeply emarginate medio-apically. Tergum 10 wide and subangulate to subtruncate medio-apically ( Fig. 129), with two long subapical macrosetae and two apical setae. Sternum 9 with moderate triangular emargination apically, two long subapical macrosetae and one apical seta at each side ( Fig. 128). Aedeagus with median lobe gradually narrowed from base of paramere; apex of median lobe acute (in dorsal view) and simple in its apical fourth (in lateral view); paramere elongate and entire, leaf-like, with apex acute, almost reaching apex of median lobe, with two lateral rows of sensory peg setae joined at apex ( Figs. 130, 131). Internal sac with distinctly sclerotized structures ( Fig. 130).

Female genitalia. Tergum 10 similar to that of male. Second gonocoxite with 2–5 strong setae along its outer margin and two long apical setae, without stylus.

Geographical distribution. P. sericans is widely distributed in North America ( Canada, USA and Mexico) and part of South America ( Argentina and Brazil), where it was recorded from the Chaco, Pampa and Parananense biogeographical provinces of the Neotropical region ( Fig. 150).

Bionomics. Philonthus sericans is a very common species in cow droppings in open and wooded habitats (Chani-Posse 2004) and it was also cited from decaying organic matter ( Smetana 1995). According to information on labels, it was also found in riverine and palm forests, and collected by flight intercept traps. Philonthus sericans , like other species of Philonthus , has long been cited for its common occurence in dung, and also as an important predator of immature flies ( Hunter et al. 1991; Hu & Frank 1997; Cabrera Walsh & Chani Posse 2003).

Type material. Gravenhorst (1802: 172) described both species, P. sericans and its junior synonym P. brunneus , from specimens from North America. I was not able to see the original material but there is little doubt that this species, as interpreted later by Smetana (1995), is the species that Gravenhorst described.

Additional material: 65 specimens (21 ♂, 24 ♀, 20 unsexed) ARGENTINA: Entre Ríos: Concordia , 19/XI/1998, M. Chani Posse , 4 specimens ( IMLA). Formosa: P.N. Rio Pilcomayo , 50km NW Clorinda, 19.XII.1990, S & J. Peck, FMHD #90-290, marsh edge, 90–122, uv light , 4 specimens ( FMNH). Misiones: P. N. Iguazu: Cantera , 8.XII.1990 – 6.I.1991, S & J. Peck, 180m ,

FMHD #90-262, old gravel pit at forest edge, 90–95, FIT, 1 ♂, 1 ♀ ( FMNH) ; Empalme 101, 8.XII.1990 – 6.I.1991, S & J. Peck, 206m, FMHD #90-266, palm forest, 90–95, FIT, 3 ♂, 9 ♀, 2 specimens ( FMNH) ; Puerto Canaos , 8.XII.1990 – 6.I.1991, S & J. Peck, 180m, FMHD #90-262, river forest, 90–95, FIT, 16 ♂, 19 ♀ ( FMNH) ; Richter , Bernhauer determ., " Philonthus brunneus Grav. ", 3 specimens ( MLPA) ; C. Bruch, Bernhauer determ., " Philonthus brunneus Grav. ", 2 specimens ( MACN) . Tucumán : El Cadillal, 22.VI.1998 y 5.I.1999, col. M. Chani Posse, 1 ♂, 3 ♀ ( IMLA) ; 5 Oct 1927, " Typus ", 3166, Philonthus Tucumán ensis Bernh., 5 specimens ( MACN) ; 1 Oct 1929, H. E. Box leg., 2720, in yellow in Bernahuer handwriting " jaynesi Bernh. Typus don. Bruch", Chicago NHMus Bernhauer Collection, 1 ♂ ( FMNH) ; Tafi ViejoEl Cadillal , 5-I- 1999, M. Chani Posse, 1 specimen ( IMLA) . BRAZIL: Santa Catharina: N. Teutonia, Plaumann , jaynesi Brnh det. Bernhauer, Plaumann 1940, Chicago NH Mus .

M. Bernhauer collection, 2 ♂, 1 ♀ ( FMNH) .