New host records for European Acroceridae (Diptera), with discussion of species limits of Acrocera orbiculus (Fabricius) based on DNA-barcoding.

New European host records for the Acroceridae species Acrocera orbiculus (Fabricius) and Ogcodes reginae Trojan are reported. Acrocera orbiculus was reared from Amaurobius erberi (Keyserling), and O. reginae from Clubiona leucaspis (Simon) and Evarcha jucunda (Lucas). Where possible, DNA-barcodes are presented for reared endoparasitoids and their host specimens. Based on mitochondrial COI, the intraspecific genetic variability of 15 western Palaearctic A. orbiculus is discussed. Maximum likelihood analysis reveals two clades, though they have low statistical support and no distinct barcoding gap. Therefore, we consider all barcoded specimens of A. orbiculus to be a single biological species with a high degree of phenotypic plasticity regarding body size and coloration. Based on molecular and morphological evidence, Paracrocera kaszabi Majer, Paracrocera manevali Séguy and Paracrocera minuscula Séguy are placed in synonymy with A. orbiculus. The male of the Canary Islands endemic Acrocera cabrerae Frey is described for the first time.