Systematic revision of the sibling species belonging to the Pristaulacus compressus group (Hymenoptera: Aulacidae)

The Pristaulacus compress us species group is revised and illustrated. It has a strictly western Palearctic range and includes four sibling species, two of which are newly described: P. rapuzzii Turrisi, sp.n. (Lebanon) and P. samai Turrisi, sp.n. (Syria). Besides external characters of the tagmata, especially the sculpturation and shape of the head and occipital carina, the taxonomic treatment of this species group takes into account new diagnostic features of the male genital capsule, including the general shape and the shape of the apex of the paramere, lamina volsellaris and penis valve. The previous key for identification of the Palearctic species of Pristaulacus is modified to include the two new species. A discussion on taxonomy, biogeography and host preference of the treated species is provided.