Revision of Holarctic Illidops Mason (Hymenoptera, Braconidae): A first step towards resolving a dark taxon and descriptions of three new species

Microgastrinae wasps are an important group of Lepidoptera parasitoids, but also considered a so-called “dark taxon” due to the large amount of undiscovered and unidentifiable diversity. In the Holarctic, this is due to various factors, but lack of up-to-date identification literature and taxonomic revisions is a main contributor. Here, the genus Illidops is revised in the Holarctic region for the first time in over 35 years and an updated generic concept is provided. Illidops albostigmalis van Achterberg & Fernandez-Triana, 2017 is recorded for the first time from the Palearctic and three new species are formally described: Illidops oroseira Höcherl & Fernandez-Triana sp. nov. from the Palearctic, Illidops doreenae Höcherl & Fernandez-Triana sp. nov., and Illidops stefanschmidti Höcherl & Fernandez-Triana sp. nov. from the Nearctic. A key to all 33 species of Illidops occurring in the Holarctic is provided. A first-glance preliminary system is used to evaluate the robustness of species concepts, allowing the inclusion of poorly known species. Many species are associated with new information, including photographs for 29 species, 23 of which are of primary types. Our integrative taxonomy approach including DNA barcoding resulted in nine species now linked to barcodes and the discovery of morphologically cryptic diversity. Shotgun-sequencing was applied for the recovery of barcode sequences of historical specimens. Additionally, annotated translations of original descriptions in Russian for six species and a commented overview of the literature of host species of Illidops are provided.