Oxypoda tarda Sharp, 1871

Assing, Volker, 2012, On the taxonomy and natural history of Oxypoda brachyptera and O. tarda (Coleoptera: Staphylinidae: Aleocharinae), Beiträge Zur Entomologie = Contributions to Entomology 62 (6), pp. 207-224 : 218-222

Oxypoda tarda Sharp, 1871 ( Figs 8-14 , 19-23 , 28 )

Oxypoda tarda Sharp, 1871: 192 .

Type material examined:

Lectotype , present designation: “1066 [written on reverse side of mounting label] / brachyptera Steph. , ferruginea Er. , forticornis Fairm. / tarda / Syntype / D. Sharp Coll. B. M. 1932-116 / Lectotypus  Oxypoda tarda Sharp , desig. V. Assing 2011 / Oxypoda tarda Sharp , det. V. Assing 2011 ” ( BMNH). Paralectotypes: 1 : “1066 [written on reverse side of mounting label] / tarda Sharp. / Syntype / D. Sharp Coll. B. M. 1932-116” ( BMNH); 3 : “1066 [written on reverse side of mounting label] / Syntype / D. Sharp Coll. B. M. 1932-116” ( BMNH); 1 : “1066 [written on reverse side of mounting label] / tarda / Syntype / D. Sharp Coll. B. M. 1932-116” ( BMNH); 1 : “1066 [written on reverse side of mounting label] / O. tarda Sharp / brachyptera Steph. , forma major, obscura / Syntype / D. Sharp Coll. B. M. 1932-116” ( BMNH); 1 : “1066 [written on reverse side of mounting label] / O. tarda type. D. S. / Syntype / D. Sharp Coll. B. M. 1932-116” ( BMNH).

Comment:

The original description is based on several syntypes (“all the specimens I have seen”) from “the salt marshes near Dumfries” ( Sharp 1871). Eight syntypes were located in the Sharp collection at the BMNH. One of the two males is designated as the lectotype. According to Booth (e-mail 3 Oct., 2011), Sharp´s catalogue number 1066 refers to Caelaverock on the coast just south of Dumfries, 25 May 1867. According to the description, O. tarda is distinguished from O. brachyptera by larger body size, darker coloration, the uniformly dark coloration of the abdomen, relatively somewhat shorter and more slender antennae, and slightly longer elytra.

Additional material examined:

Apart from the material listed in Tab. 2 , the following material was studied:

Germany: Niedersachsen: 1  [macropterous], Hannover, Osterfelddamm, pitfall, VIII-IX.1991, leg. Sprick (cAss); 1  [micropterous], W Hannover, Haste , arable land, VI.1987 (cAss); 1  [micropterous], Süntel , Rannenberg , calcareous arable land, pitfall, VI.1987, leg. Sprick (cAss); 1  [micropterous], same data, but V.1988 (cAss); 2  [micropterous], Bückeburg env., Ahnsen , shrubs, pitfall, VI.1986, leg. Sprick (cAss); 1  [micropterous], same data, but meadow, XII.1985 (cAss); 1  [macropterous], same data, but arable land, VII.1986 (cAss); 1 , 2 exs. [micropterous], Stadthagen, moist forest clearing, pitfall, VIII-IX.1991, leg. Sprick (cAss); 1  [micropterous], Harz, St. Andreasberg , 700 m, pitfall, VIII-IX.1991 (cAss); 1  [macropterous], Herzberg, 200 m, Oder floodplain, VII.1992 (cAss); 3 , 1  [macropterous], Braunschweig env., Hötzum, arable land, VI.1988 (cAss); 1  [macropterous], Braunschweig, arable land, VI.1988 (cAss) . Schleswig-Holstein: 1  [micropterous], Neustadt in Holstein env., Brodau , 30.IV.1989 (cAss); 33 exs. [16 macropterous], Husum env., Beltringharder Koog [54°33'N, 8°55'E], salt marsh, meadow, pitfall, V-X.1991 (cAss) . Hessen: 2  [micropterous], Hanau env., Schlüchtern , pitfall, VII.1993, leg. Sprick (cAss) . Nordrhein-Westfalen: 1  [micropterous], Höxter env., Beverungen , pitfall, 17. V.1990 (cAss) .

Diagnosis:

Body length 2.5-3.0 mm. Coloration similar to that of O. brachyptera and similarly variable, but specimens of darker coloration are more common than in O. brachyptera . Body shape on average slightly broader than in O. brachyptera .

Elytra dimorphic, in micropterous morph 0.75-0.90 times, in macropterous morph 0.90- 0.95 times as long as pronotum. Hind wings either fully developed (macropterous morph) or reduced to short stubs (micropterous morph), these rudiments slightly longer than elytra.

Abdomen punctation of tergite VII practically as dense as that of anterior tergites ( Fig. 10 ); posterior margin of tergite VII with palisade fringe in both morphs.

Other external characters (punctation, microsculpture, etc.) as in O. brachyptera ( Figs 8-9 ).

: sternite VIII of similar shape as that of O. brachyptera ( Fig. 11 ); median lobe of aedeagus 0.38-0.40 mm long, of similar morphology (including internal structures) as that of O. brachyptera , but apex of ventral process more acute in lateral view and internal structures longer ( Figs 19-23 ).

: sternite VIII of similar shape and chaetotaxy as that of O. brachyptera ( Fig. 12 ); spermatheca of similar shape as that of O. brachyptera , but apical cuticular intrusion slightly less deep ( Figs 13-14 ).

Comparative notes:

Oxypoda tarda is most reliably distinguished from the extremely similar O. brachyptera by the larger median lobe of the aedeagus (no overlap) and the more acute apex of the ventral process of the aedeagus in lateral view (see Figs 15-17 and Figs 19-22 ). Additional, but less reliable characters are the on average longer elytra (in both morphs), the on average darker coloration, the on average larger and broader body, and the more densely punctate abdominal tergite VII (see Figs 3, 10 ).

Distribution:

According to Smetana (2004), the distribution of O. tarda is confined to Denmark, Sweden, and Germany. Remarkably, Great Britain is not listed in the catalogue, although the species was described from Scotland. For additional records from Germany, Denmark, and Sweden see Baranowski (1979), Brenner (1993), Feldmann & Lückmann (1998), Hansen et al. (1995), Hennicke & Müller-Motzfeld (1998), Klausnitzer et al. (1980), Köhler (1997), Korge (1990), Kunze & Kache (1998), Lundberg (1978a-b), Renner (2001), Rose (2000), Vogel (1978, 1980), and Vogel & Dunger (1980); references with obviously doubtful records from habitats that are generally inhabited by O. brachyptera are not included. It appears likely that O. tarda is much more widespread, but owing to its similarity to, and the previous confusion with O. brachyptera , it is unknown which of the literature records of O. brachyptera in fact refer to O. tarda .

Natural history:

Habitat. In northern Germany, O. tarda is not particularly rare. The examined material was found in various unforested, generally in more or less moist habitats on heavier, often more or less loamy, or on calcareous soils, particularly in moist meadows, floodplains, arable land, fallows, and in coastal meadows. The species appears to be absent from dry habitats on sandy soils.

According to Lohse (1974), O. tarda occurs in the same localities as O. brachyptera . However, the present data do not confirm this observation. In the vast majority of the studied sites, only either of the two species was present. Both species were recorded as syntopic only in a coastal meadow, in arable land, and in a fallow. In most cases of syntopic occurrence, at least one of the two species was represented exclusively by the macropterous morph. In localities where either of the two species was very abundant, the other species was always absent ( Tab. 2 ). Thus, regarding their respective habitats, O. tarda and O. brachyptera appear to be clearly segregated.

Phenology:

The epigeic activity period measured with pitfall traps in 1986/1987 lasted from May to the first half of November. The highest activity was observed from the second half of May through June and in September ( Fig. 28 ). The sex ratio (males:females) was similar to that of O. brachyptera (1.27). Mature eggs were found in the ovaries of dissected females from the second half of June through the first half of August. Teneral adults were observed from the second half of August through September, with a maximum in the second half of September. These data suggest that O. tarda has only one generation per year, that the duration of pre-imaginal development is similar to that of O. brachyptera (1.5-2 months, without diapause), and that hibernation occurs in the adult stage.

Pterodimorphism:

As in O. brachyptera , the micropterous morph of O. tarda is much more common than the macropterous morph ( Tab. 2 ). At least this is true of the study sites where the species was abundant. Higher proportions of the macropterous morph were observed only on arable land and in a salt meadow. The flight muscles were not studied, and flying specimens have not been recorded.

Figures

Figs 1-14: Oxypoda brachyptera (1-7; 6: syntype) and O. tarda (8-14; 11: lectotype; 13: paralectotype): median portion of pronotum (1, 8); median portion of elytra (2, 9); abdominal tergites VI-VIII (3, 10); male sternite VIII (4, 11); posterior portion of female sternite VIII (5, 12); spermatheca (6-7, 13-14). Scale bars: 4, 11: 0.2 mm; 1-3, 5-10, 12-14: 0.1 mm.

Figs 15-23: Oxypoda brachyptera (15-18) and O. tarda (19-23; 22: lectotype): median lobe of aedeagus in lateral view (15-17, 19-22); apical portion of median lobe in ventral view (18, 23). Scale bar: 0.1 mm.

Fig. 28: Pooled seasonal activity density of O. tarda based on pitfall trap studies in Hannover in 1986/1987 (total: 442 specimens). For additional explanations see Fig. 25.