Abstract
New tribe Twangsteini trib. nov. (Hymenoptera, Ichneumonidae, Pimplinae) including a new genus Twangste gen. nov. with a new species T. belokobylskiji sp. nov. is described from Late Eocene Baltic amber. It is supposed that the tribe Twangsteini is an extinct, basal and at the same time strongly advanced phylogenetic lineage of Pimplinae. This inference is based on a number of characters of similarity with the Mesozoic subfamily Labenopimplinae and a number of features of apomorphy and plesiomorphy. Morphological similarity with the recent group of genera “Polysphincta” is the basis for assumption that Twangste developed as a parasitoid on adult spiders (Arachnida, Araneida) or in their egg cocoons, and this biology is supposed to be primary for the Polysphincta genus group.