Cercyon obsoletus ( Gyllenhal, 1808 )

Vorst, Oscar, 2009, Cercyon castaneipennis sp. n., an overlooked species from Europe (Coleoptera: Hydrophilidae), Zootaxa 2054, pp. 59-68 : 62-65

Cercyon obsoletus ( Gyllenhal, 1808)

( Figs. 2 , 4, 6 , 10–12 , 14 )

Sphaeridum lugubre : Olivier 1790: (No.15) 7. (misinterpretation of Dermestes lugubris Fourcroy, 1775 ).

Sphaeridium atomarium: Paykull 1798: 58 . (misinterpretation of S. atomarium sensu Fabricius, 1792 , being itself a misinterpretation of Silpha atomaria Linnaeus, 1767 ).

Sphaeridium obsoletum Gyllenhal, 1808: 107 . Type locality: ‘Suecia’ [ Sweden].

? Cercyon obsoletum var. tristis Dalla Torre, 1877: 73 .

? Cercyon obsoletum var. obscurus Dalla Torre, 1877: 73 .

Diagnosis. A large Cercyon s. str., very similar to C. castaneipennis sp. n. It differs at first glance from this species by the more dull overall appearance, and the usually piceous black colour of the elytra ( Fig. 2 ). Table 1 summarizes the differences between both species.

Description. Body length: 3.25–4.20 mm (median 3.75 mm, N = 20). Elytral length (apex of scutellum to apex of elytra): 2.25–2.80 mm (median 2.55 mm, N = 20). Elytral width: 2.05–2.45 mm (median 2.20 mm, N = 20). Black; elytra usually piceous black, paler towards the apex, apical fifth usually reddish brown ( Fig. 4 ); sometimes elytra completely brown, anteriorly darkened, but never with a distinct basal macula as in C. castaneipennis . Humeri with a tiny unobtrusive brown spot at the base of 6th elytral stria.

Head, pronotum and elytra with fine and dense punctuation, somewhat denser than in C. castaneipennis and as a result more dull than in this species. Elytral striae poorly defined, inner striae becoming almost obsolete anteriorly; as a result striae less clear than in C. castaneipennis . Elytra rather wide, slightly less convex than in C. castaneipennis , less strongly narrowed posteriorly, lateral margin regularly curved, unlike in C. castaneipennis . Lateral margin of elytra immediately behind anterior angle with a tiny transverse plica, as in C. castaneipennis .

Raised middle portion of mesoventrite narrow (length: width = 3.4–4.4, median 4.1, N = 10), somewhat less slender than in C. castaneipennis . Metaventrite without femoral lines.

Maxillary palpi and antennae dark piceous to black. Antennal club somewhat less elongate (length: width = 1.6–1.9, median 1.8, N = 10) and as a rule slightly paler than in C. castaneipennis ( Fig. 6 ). Mentum with punctuation clearly separated, not or only to very limited extent fused to form transverse wrinkles. Legs piceous to brown, tibia paler than femora, tarsi paler than tibia; in general a trifle paler than in C. castaneipennis .

Male genitalia ( Figs. 10–12 ) similar to that of C. castaneipennis , but relative length larger (aedeagal length: elytral length = 0.39–0.43, median 0.41, N = 15) and relative length of basal piece (BP) more than in this species (parameral length: BP length = 0.53–0.67, median 0.61, N = 15). BP with a more limited asymmetrical emargination basally.

Type material. Sphaeridium obsoletum Gyllenhal : Lectotype (by present designation) (in poor condition, lacking head, left elytron and all inner tissues): [no original label], " Sphaeridium obsoletum / GYLL #5979 / 161: 51", " Lectotypus / Sphaeridium obsoletum Gyllenhal, 1808 / design. O.Vorst 2008" ( UUZM, Collection L. Gyllenhal).

Material examined. IRELAND: Monaghan: 3, Ballybay, 17.viii.1961, P. Staffeleu ( RMNH). THE NETHERLANDS: Province of Drenthe: 1 spec., Ansen, 14.iv.1979, F.C.F. Sterrenburg ( ZMAN); Province of Gelderland: 1 spec., Arnhem, Terletsche Heide, 17.iv.1997, carcass of Highland cattle, J. Huijbregts (cJH); 3 spec., Driel, 6.viii.1968 (3, Ƥ), 4.vi.1979 (1 spec.), S. van Heijnsbergen ( ZMAN); 2 33, Imbosch, Lamsgroen, 18.iv.2003, carcass of Highland cattle in forest, O. Vorst (cOV); 1 spec., Nunspeet,. iv.1920, D. MacGillavry ( ZMAN); 1 spec., Wageningen, 4-9.vi.1963, A.C. Nonnekens ( ZMAN); 3, Zaltbommel, Kil van Hurwenen, 18.i.2004, flood refuse, F. van Nunen (cFN); Province of Noord-Holland: 1 spec., Amsterdam, Amsterdam CS, 1.vi.1993, J.H. Woudstra ( ZMAN); 1 spec., Hilversum, 16.iv.1922, P. van der Wiel ( ZMAN); 1 spec., Koedijk, Kleimeer, 26.vi.1982, manure heap, H. Vallenduuk ( ZMAN); 1 spec., Vogelenzang, 24.iv.1965, v.d. Laan ( ZMAN); Province of Zuid-Holland: 3, Ƥ, Rozenburg, Landtong van Rozenburg, 5.v.2008, cattle dung in meadow, O. Vorst (cOV); Province of Noord-Brabant: 3, 2 ƤƤ ( Fig. 2 ), Biesbosch, De Dood, 18.iv.2007, carcass of roe deer, O. Vorst (cOV); Ƥ, 1 spec., Biesbosch, Verschurepolder, 8.x.2005, cattle dung in meadow, O. Vorst (cOV); 3, Woudrichem, River Waal, 20.ii.2005, flood debris, F. van Nunen (cFN); Province of Limburg: 1 spec., Epen, 1914, A.J. Zöllner ( ZMAN); 1 spec., Gronsveld, 22.iv.1962, P. Poot ( ZMAN); 1 spec., Maastricht, 27.v.1938, C.M.C. Brouérius van Nidek; 3 ƤƤ, 1 spec., 't Rooth, 9.vi.2007, flood refuse in limestone quarry, O. Vorst (cOV). Some further 51 Dutch specimens were examined. FRANCE: Département Cantal: 3, Yolet, 26.vii.1985, E.A.M. Speijer ( RMNH); Département Hautes-Alpes: 3, Reotier, 26.vii-8.viii.1987, 1000 m ASL, A. Teunissen ( RMNH); Département Lot: Ƥ, Gourdon, 21.ix.1983, P. Kanaar ( RMNH); Département Pyrénées-Atlantiques: Ƥ, Harambeltz, 16.vii.1990, E.A.M. Speijer ( RMNH); Département Yonne: 3, Tonnerre, 7.vii.1975, A.C. van Dijk ( RMNH). FRANCE or SWITZERLAND: 1 spec., Jura, Piaget ( ZMAN). SWITZERLAND: Kanton Uri: 3, Maderanertal, 22.vi.1938, Excursie Leidsche Biologen ( RMNH); Kanton Waadt: 1 spec., Chesières, 7-13.vi.1897 ( NMPC); 1 spec., Chesières, 13.vi.1905, Hlisnikowski ( NMPC). SPAIN: Cantabria: 3, 15 spec., Santillana, 4-5.v.1958, Excursie Spanje ( RMNH); Navarra: 3, Ƥ, Burguete, 24.vii.1988, E.A.M. Speijer ( RMNH); Sevilla: Ƥ, Lebrija, 9-10.v.1960, Excursie Spanje ( RMNH). ITALY: Campania: 1 spec., ‘Neapel’ [Napoli], 13.v.1903, Hlisnikowski ( NMPC); Sardegna: Ƥ, 4 spec., Bonarcado, 1.v.1982, P. Kanaar ( RMNH); 3, Laconi, 24.iv.1982, P. Kanaar ( RMNH); 3, Nurallao, 24.iv.1982, P. Kanaar ( RMNH). GERMANY: Bayern: 3, 3 spec., ‘Bavaria’, F.C. Visser ( RMNH). AUSTRIA: Tirol: 1 spec., ‘Tirol’,. vi.1959, v.d. Laan ( ZMAN). ROMANIA: 1 spec., ‘Rumaenia’, Reitter ( ZMAN). GREECE: Attiki: 2 spec., ‘Attika’, Emge ( ZMAN). MOROCCO: Meknès-Tafilalet: 1 spec., Ifrane, 11.v.1995, J. Hájek ( NMPC); Tangier-Tétouan: 13, 2 spec., between Bad Berret and Bad Bessen, 3-6.vi.2007, around Fagus trees near rock (sifted), P. Hlaváč ( NMPC); 8 spec., Bad Bessen, 3.vi.2007, around Fagus trees (sifted), P. Hlaváč ( NMPC). ALGERIA: Alger: Ƥ, Alger, Richt[er]? ( RMNH). TUNISIA: Jendouba: 3, 9 spec., Ain Draham, B. von Bodemeyer ( NMPC, RMNH). IRAN: 2 spec., ‘Elburs-Gebirge’ [Alburz mountains], B. von Bodemeyer ( ZMAN).

Distribution ( Fig. 14 ). Confirmed records from a large part of the Mediterranean (including North- Africa), Ireland, Central Europe ( The Netherlands, Germany, Switzerland and Austria) and Iran (not mapped). Cercyon obsoletus s. l. has further been reported from several other Central and East European countries (e.g. Czech Republic, Poland, Belarus, Russia), as well as from the southern part of Fennoscandia, the Azores, Canary Islands and Armenia ( Hansen 2004, Palm 1977). Hansen (1999) reports this species as doubtfully introduced into Argentina. However the publication of Bruch (1927) that he refers to, does not mention this species. The supposed occurrence in the Neotropical Region is thus erroneous.

Bionomics. Mainly in dung of larger herbivores, but also recorded from carrion and manure. Most examined specimens were collected from April through October. In addition two specimens were collected from riverine flood refuse in January and February, indicating the species overwinters (at least in part) as an adult.

Remarks. The Gyllenhal collection kept at UUZM holds a single pinned specimen standing as Sphaeridium obsoletum , which clearly fits his original description ( Gyllenhal 1808). It is in poor condition, probably damaged by Psocoptera. The elytral punctuation however suffices to determine its identity.

For a long time this species was named Cercyon lugubris (Olivier, 1790) ( Huijbregts 1982, Knisch 1924, Porta 1929, Vogt 1969, 1971). This name is, however, not available as Olivier did not describe it as new, but attributed it to Fourcroy (1785), by referring to Fourcroy's Dermestes lugubre . It is believed that Olivier misinterpreted Fourcroy's species ( Mulsant 1844, Hansen 1987, 1999) and was actually the first to recognize the species. His interpretation is here listed as synonym of C. obsoletus , not C. castaneipennis , based on the description: “Le corps est noir ...” [the body is black ...] (Olivier 1790).

Gyllenhal (1808) introduced the name in current use, Sphaeridium obsoletum . He not only considered it conspecific with Olivier’s Sphaeridium lugubre , but also with Paykull’s (1798) interpretation of Sphaeridium atomarium sensu Fabricius, 1792 , being itself a misinterpretation of Silpha atomaria Linnaeus, 1767 (now in Stilbus Seidlitz, 1872 ). Paykull’s descriptions fits C. obsoletus not C. castaneipennis : “Elytra ... nigra, apice indeterminate rufescente ...” [Elytra ... black, apex diffusely reddish] ( Paykull 1798).

Recent catalogues ( Hansen 1999, 2004) mention just two junior synonyms of Cercyon obsoletus : Cercyon obsoletus var. tristis Dalla Torre, 1877 and C. obsoletus var. obscurus Dalla Torre, 1877 . Dalla Torre introduced these names for specimens with black, respectively brown elytra: “Fld. schwarz ( var. obscurus m.) oder braun ( var. tristis m.), ... Spitze der Fld. rothbraun” [Elytra black ( var. obscurus m.) or brown ( var. tristis m.), ... apex of elytra reddish brown] ( Dalla Torre 1877). Dalla Torre’s concept of C. obsoletus might be erroneous as he mentions a body length of 2–3 mm only. The interpretation of both names as doubtful synonyms of Cercyon lugubris is based on Knisch (1924). The first is a secondary homonym of Sphaeridium triste Illiger, 1801 , the second of Hydrophilus obscurus Fabricius, 1792 , a junior synonym of Cercyon haemorrhoidalis ( Fabricius, 1775) ( Hansen 1999) , rendering both names unavailable. Types are most probably lost, as the Dalla Torre collection was destroyed during the Second World War ( Jäch 1988).

Figures

FIGURES 1 – 2. Habitus of Cercyon castaneipennis (1) and C. obsoletus (2). Scale bar 1.0 mm. Photographs by Th. Heijerman.

FIGURES 3 – 6. Elytral colour pattern and antennae of Cercyon castaneipennis (3, 5) and C. obsoletus (4, 6). 3 – 4. Elytral colour pattern, scale bar 0.5 mm; 5 – 6. Antenna, scale bar 0.2 mm.

FIGURES 7 – 12. Male genitalia of Cercyon castaneipennis (7 – 9) and C. obsoletus (10 – 12), dorsal aspect. 7, 10. Basal piece and parameres; 8, 11. Penis; 9, 12. Sternite IX. Scale bar 0.2 mm.

FIGURES 13 – 14. Distribution of Cercyon castaneipennis (13) and C. obsoletus (14) on a 100 km UTM grid. The record of C. obsoletus from northern Iran is outside the area shown.