Sycophila binotata Fonscolombe, 1832

Figs 13–14

Identification

This species keyed easily in Zerova (1978 – as Eudecatoma binotata) and agrees with the concept of Z. Bouček and M. Graham (Graham 1992), based on the lectotype designated by Graham, and specimens determined by Bouček and Graham in BMNH, and was confirmed by R. R. Askew (pers. comm.). The species is highly distinctive among European Sycophila in having two dark fasciae on each fore wing.

Material examined

ENGLAND: London, Fulham, Imperial Wharf, TQ263765, ♀, ex gall of Aphelonyx cerricola on Quercus suber, gall coll. 21 Mar. 2010, M. Barclay, BMNH (E)969429; ♀, same data, except gall coll. 26 Sep. 2011, BMNH (E)969430.

Distribution

S. binotata has a widespread distribution in southern Europe including Spain, France, Italy, and the Balkans (Noyes 2013; Askew et al. 2013), although it was not recovered during a recent survey of parasitoids of A. cerricola (Giraud, 1859) in central Europe (Melika et al. 2002). It is recorded here as new to Britain.

Biology

British material of S. binotata was reared from the galls of Aphelonyx cerricola collected from Quercus suber L. The exact insect host was not established, since other inquiline and parasitoid Hymenoptera were also present as well as the gall causer; however, it has apparently not been reared from galls of Aphelonyx previously (Melika et al. 2002; Askew et al. 2013) and is normally an oligophagous endoparasitoid of Plagiotrochus spp. (Cynipidae) on evergreen species of Quercus L. of sections Cerris Loudon and Ilex Loudon (Gómez et al. 2013). The history of the Quercus suber trees which hosted the British S. binotata is of some interest – they were planted as well-established saplings during the winter of 2005–2006, and their origin is most likely to have been Italy; novel Coleoptera found in association with these trees are likely to have come from Italy and an Italian coin was found in the soil around their roots (M. V. L. Barclay pers. comm.), so it seems likely that the S. binotata was imported with the trees direct from Italy and has survived for several generations in Britain.

Remarks

If, as seems likely, S. binotata was imported together with its gall wasp host and host tree, this is of considerable interest for studies of the recruitment of parasitoids of invasive gall wasps in the UK. Some previous studies of the parasitoids of invasive gall wasps in the UK have considered two main methods of recruitment, either recruitment from an existing pool of native parasitoids, or that populations of parasitoids might pursue host gall wasps as they spread continuously across Europe, the former appearing more likely (Schönrogge et al. 2006, 2011). However, the presence of the previously non-British S. binotata in London, in circumstances where good-sized trees were imported, raises a third, more radical possibility, that recruitment is not necessary when parasitoids are not lost by their cynipid hosts. Oak trees could be imported through the horticulture trade with a community of gall wasps and parasitoids more or less intact; this would of course be much faster than the unassisted, or partially assisted, spread of both gall wasp and parasitoid. It is of course possible that other parasitoids have also been imported in this way; such introductions may be easily overlooked, especially where the same species already occurs in Britain. Without historical evidence of the circumstances of importation of host gall wasps, such instances could have been misinterpreted as recruitment from the existing pool of native parasitoids, so caution is needed when interpreting recruitment studies of such imported gall wasps. Given the numbers of good-sized oaks used in the UK for prestigious building developments and parks, in particular Quercus ilex L. and its associated gall wasp species, e.g., Plagiotrochus Mayr, 1881, the potential for other parasitoids to be introduced in this way is clear.