Philonthus rectangulus Sharp, 1874

Chani-Posse, Mariana, 2010, Revision of the southern South American species of Philonthus Stephens (Coleoptera: Staphylinidae) 2595, Zootaxa 2595, pp. 1-70 : 47-49

Philonthus rectangulus Sharp, 1874

(Figs. 5, 7, 15, 111–115, 146)

Philonthus rectangulus Sharp, 1874: 42 . For complete references see Herman (2001b).

Diagnosis. Philonthus rectangulus may be identified by its body shape, the eyes distinctly longer than temples seen from above, and the first three abdominal terga with posterior basal line acutely extended. It differs from other southern South American species of Philonthus by the distance separating medial interocular punctures on frons less than twice as large as distance separating medial punctures from lateral punctures, the submentum about 2.5 times as long as mentum, and the transverse distance between punctures on elytra about as large as diameters of punctures.

Redescription. Length of the body 8.8–10.6 mm. Coloration. Head black to piceous-black; thorax and elytra castaneous, shiny; abdominal segments castaneous-piceous with apical margins lighter; antennae castaneous-brunneous, palpi and legs brunneous.

Head distinctly to moderately wider than long (HW/HL= 1.6–1.2) (Fig. 5) and at basal third as wide as distal third in both sexes, about as wide as pronotum (HW/PW= 1.0–0.94); 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 less than twice as large as distance separating medial punctures from lateral punctures; infraorbital ridge present, extending not far beyond postgenal ridge; postmandibular ridge present. Eyes distinctly to moderately longer than temples (EL/TL= 1.5–1.2) seen from above (Fig. 5). Antennae with segment 1 as long as segments 2 and 3 combined, segments 2 and 3 subequal in length, segments 4–5 elongate, 6 quadrate, segments 7–10 gradually transverse. Maxillary palpus with segment 2 not swollen, no more than twice as long as its maximum width; last segment fusiform, about 1.5 times longer than segment 3. Posterior arms of gular sutures running close to each other until the base of head, either joined before neck or not. Submentum about 2.5 times as long as mentum (Fig. 7). Labial palpus with last segment twice as long as preceding segment. Neck more than 0.5 times as wide as head at widest point (NW/HW= 0.7–0.6).

Pronotum about as long as wide (PW/PL= 1.0–0.9), parallel-sided; dorsal surface of pronotum with two rows of punctures, each with five punctures, rarely four (if four, only at one row). Hypomeron not visible in lateral view. Basisternum with medial longitudinal carina moderately developed, bulbous. Metasternum with circum-mesocoxal 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 diameters of punctures (Fig.). Both front and middle tarsi as long as front and middle tibiae; first segment of hind tarsus as long as segments 2 and 3 combined, and longer than last segment (S1/S5= 1.25–1.16). Abdominal terga distinctly punctuate at basal area, distance separating punctures smaller than diameters of punctures; terga 2 and 3 with elevated area between basal lines punctuate, posterior basal line acutely extended medially ( Fig. 15). Male sternum 7 with apical margin straight. Tergum 8 in both sexes with posterior margin arcuate.

Male genitalia. Sternum 8 moderately emarginate medio-apically. Tergum 10 truncate medio-apically, with two long subapical macrosetae and 8–10 short apical setae. Sternum 9 with a concave emargination apically with one long apical seta at each side. Aedeagus with median lobe gradually narrowed from apical third; apex of median lobe subacute (in dorsal view) and simple in its apical fourth (in lateral view); paramere divided into two branches along most of its length, both close to each other reaching four fifths of median lobe length, each with 5–8 sensory peg setae at apex ( Figs. 112–114). Internal sac with no distinctly sclerotized structures.

Female genitalia. Tergum 10 wide and subangulate apically, with two long subapical macrosetae and 8–10 short apical setae ( Fig. 111). Second gonocoxite with 2–5 strong setae along its outer margin, with stylus and with two long apical setae ( Fig. 115).

Geographical distribution. Philontus rectangulus is currently considered a cosmopolitan species, originally known from Japan ( Smetana 1995). In the Neotropical region it is known at present from Cuba, Costa Rica, Brazil, Uruguay, Argentina and Chile ( Fig. 146).

Bionomics. Philonthus rectangulus , like other species of Philonthus , has been frequently found in cow and horse droppings and it has long been cited for its high abundance at dung in open and wooded habitats, also as an important predator of immature flies ( Hunter et al. 1991; Hu & Frank 1997; Cabrera-Walsh & Chani-Posse 2003). Smetana (1995) also mentioned P. rectangulus from other organic matter, particularly in disturbed habitats near human settlements. Frank (1982) also cites this species as parasitized by Laboulbeniales (Fungi, Ascomycetes).

Type material. Sharp (1874: 42) described the species from specimens from Nagasaki, Japan. I was not able to see the original material but there is little doubt that this species, as interpreted later by other authors ( Smetana 1995; Coiffait & Sáiz 1968) is the species that Sharp described.

Additional material: 22 specimens (7 ♂, 10 ♀, 5 unsexed)

ARGENTINA: Entre Ríos: Concordia , 19.XI.1998, col. M. Chani Posse, 1 ♀ ( IMLA) . Tucumán: El Cadillal , 22.VI.1998 y 5.I.1999, col. M. Chani Posse, 4 ♂, 1 ♀ ( IMLA) . Buenos Aires: Argentina, Prov. Buenos Aires, Castelar , 29 Dec. 1989, in cow dung, coll. G. Cabrera, code: dung-175, 1 ♂, 1 ♀ ( MLPA) .

BRAZIL: Sao Paulo, 7.II.71, V.N.Alin, Field Mus. Nat. Hist., 4 ♀ ( FMNH). CHILE: Curicó: Romeral, 18.IX.65, Philonthus rectangulus Det. F. Saiz 1970 , 1 specimen (C.Saiz); Las Cruces, X.1958, E. Peña leg., Field Mus. Nat. Hist., 1 ♀ ( FMNH). Santiago: El Canelo, XII.1978, L. E. Peña leg., Field Mus. Nat. Hist., 1 ♂ ( FMNH). COSTA RICA: Sn. Pedro, 8.1948, (Klifosh), 1 ( FMNH). Maipú: Rangue, 10 Oct. 2004, M. Guerrero G., 1 ♂ ( MNHN). Malleco: P.N. Nahuelbuta, vic. Pehuenco (Centro de Visitantes), 6–25.xii.2002, Thayer, Newton, Clarke, 1130m, carrion trap (octopus), FMHD 2002-049, wishrubby understory no bamboo, 1 ♀ ( FMNH); Lago Malleco, 6.xii.2002, Clarke, 1230m, in horse duna, Nothofagus antarctica Forest with Araucaria , 1 ♀ ( FMNH). CUBA: Playas Marianas, 20.VII.1929. Somonostro, 10.X.1933, 1966, A. Bierig

Colln. 1 specimen ( FMNH) . Rio Almendares , 10.X.1928, 1966, A. Bierig Colln., 1 ( FMNH) . URUGUAY: Montevideo: A. Migueletes, 10.I.1933, Colección Fernandez, Tremolleras don., 1specimen ( FMNH) .