A revision of European species of the genus Tetrastichus Haliday (Hymenoptera: Eulophidae) using integrative taxonomy.

The European species of Tetrastichus Haliday (Hymenoptera: Eulophidae) are revised using a combination of externo-morphological and DNA barcoding data. This is the first integrative approach for any of the large genera of the Tetrastichinae. A total of 93 species are included, of which 50 are described as new: T. agonus sp. n., T. antonjanssoni sp. n., T. argei sp. n., T. argutus sp. n., T. asilis sp. n., T. ballotus sp. n., T. bledius sp. n., T. broncus sp. n., T. calcarius sp. n., T. calmius sp. n., T. clisius sp. n., T. cosidis sp. n., T. cumulus sp. n., T. cyprus sp. n., T. delvarei sp. n., T. doczkali sp. n., T. elanus sp. n., T. elodius sp. n., T. ennis sp. n., T. enodis sp. n., T. erinus sp. n., T. evexus sp. n., T. fadus sp. n., T. fenrisi sp. n., T. flaccius sp. n., T. gredius sp. n., T. iasi sp. n., T. illydris sp. n., T. incanus sp. n., T. inscitus sp. n., T. intruitus sp. n., T. johnnoyesi sp. n., T. lacustrinus sp. n., T. ladrus sp. n., T. lanius sp. n., T. lazius sp. n., T. lixalius sp. n., T. lycus sp. n., T. marcusgrahami sp. n., T. minius sp. n., T. mixtus sp. n., T. nataliedaleskeyae sp. n., T. nymphae sp. n., T. pixius sp. n., T. scardiae sp. n., T. splendens sp. n., T. sti sp. n., T. suecus sp. n., T. tacitus sp. n. and T. tartus sp. n. Two keys for the identification of species are presented, one for females and one for males. Based on DNA barcode sequences for 70 of the species, a Maximum Likelihood tree to assess phylogenetic relationships within the genus is presented. These 70 species are also characterised by a combination of CO1 and morphological data. The remaining 23 species, without a DNA barcode, are characterised by morphological data. Using a combination of data from the morphology and CO1 or morphological data only, the species are separated into three species groups (clito-, hylotomarum-, murcia-groups) with 41 unplaced species outside these groups. Hosts are known for 27 of the species and they are gregarious, koinobiont endoparasitoids on a wide range of immature stages of holometabolous insects and appear to be very host specific. The first host record for Lepidoptera (Tineidae) in Europe is included.