Pteromalus isarchus Walker, 1839

Measurements. Body length: 1.7–2 (1.8) mm, maximum width: 0.8–1 (0.9) mm (n=4) ex gall Xestophanes potentillae (Retzius) .

Description. body more or less fusiform, tapering slightly anteriorly and gradually posteriorly, widest at middle (Fig. 4 F).

Head (anterior view) (Fig. 6 F). Almost hexagonal; antennal area not bulging and relatively conspicuous.

Mouth parts (Fig. 7 F). Ventral margin of the clypeus curved; labrum more or less trapezoid almost 3.3× wider than long.

Biology. The species P. isarchus is an oligophagous parasitoid of Xestophanes (Cynipidae) galls on Potentilla spp . (Fig. 9 C). It is mainly a primary ectoparasitoid of cynipid larvae and in the Palaearctic has been recorded from two different species of Xestophanes (Askew et al. 2006), although in the Iberian Peninsula it is more commonly found within the parasitoid community of X. potentillae (Garrido-Torres & Nieves-Aldrey 1990, Gómez et al. 2006).

Material examined. ex gall X. potentillae on Potentilla reptans (Rosaceae), Spain, Asturias: Ajuyán-Oviedo (07/09/2005) L. Parra leg. (n=3); Tarragona: Colldejou (14/08/2003) J. L. Nieves leg. (n=1).