Eucoiline wasps are parasitoids of Diptera larvae in various microhabitats. They are by far the most species-rich subfamily of the Figitidae but they are poorly studied in general and the classification in particular is chaotic. Here, a taxonomic revision is provided of one of the more enigmatic eucoiline groups, the Eucoila/Trybliographa complex. This group is spread over the world, but significantly one of the most abundant groups of Eucoilinae in the Holarctic.
This complex includes rather large genus Trybliographa Förster, the type genus of the subfamily, Eucoila Westwood, and the two small genera Bothrochacis Cameron and Linoeucoila Lin. In the present work, more than 500 species-level names are considered, which have at some time or another been placed in this group, and it is concluded that 156 of them truly belong to the group. The circumscriptions of these genera are emended according to phylogenetic concerns. Eucoila is restricted to the species-poor "crassinerva group", a Holarctic group comprising large species attacking various calyptrate flies in dung and similar microhabitats. Bothrochacis is extended to accomodate all the Paleotropic species previously considered to be part of Eucoila; their biology is similar to that of Eucoila. Linoeucoila was previously believed to be endemic to Taiwan, but one new species is described from South Africa, extending the distribution range of the group considerably. The species-rich genus Trybliographa was previously considered to be Holarctic and exclusively parasitising Anthomyiidae, but here it is demonstrated that the genus occurs globally, and includes species attacking other calyptrate flies. It is extended to include all the morphologically transitional forms which were previously classified in Eucoila, the "floralis group".
All the known species are treated, and many are redescribed in full-length. 19 species are described as new to science: Eucoila primorskensis from the Russian Far East, Bothrochacis malaisei from South East Asia, B. iberica from south Europe, Linoeucoila laterostriata from South Africa, Trybliographa eofloralis from the Russian Far East, T. coprophila from northern Europe, T. merdaria from central Asia, T. dislocata from South America, T. longicella from South East Asia, T. bovina from Europe, T. ferruginea from North America, T. chrestosemoida from the Himalayas, T. pymi from Europe, T. japonica from Japan, T. vandynae from Europe, T. pedunculata from Europe, T. scandica from northern Europe, T. emblematica from northern Europe, and T. ptilicola from northern Europe.
A large number of new combinations and new synonymies are made. Inside the Eucoila/Trybliographa complex, 3 new genus-level synonymies are made (Pentaplastidia Weld, Psilodoropsis Hedicke and Lenobria Belizin are new synonyms of Trybliographa), plus 45 new species-level synonymies, and 26 new combinations, while one species is removed from synonymy. An additional 142 new combinations are made of the names considered that were found not to belong within this group. Furthermore, one new genus-level synonymy (Tetramerocera Ashmead as new synonym of Ganaspis Förster) and seven new species-level synonymies are made, and six new replacement names (nomina nova) proposed; even though such nomenclatural acts have not been part of the primary scope of the paper.