LAUSR

Spider flies are a remarkable lineage of Diptera that develop exclusively as endoparasitoids of spiders; the only exception is found in the Chilean genus Carvalhoa (= Sphaerops), which remains ectoparasitic on the host for weeks after leaving its body. The group is relatively well represented in the fossil record, with some species being quite common in Baltic and Dominican amber deposits. Here we present the first comprehensive review of fossil spider flies (Diptera: Acroceridae), with morphological diagnoses and descriptions performed using modern cybertaxonomic tools. The identity of Burmacyrtus is reassessed and the genus is not considered an acrocerid. Furthermore, based on recent examinations of the type specimens of Archocyrtus gibbosus and Juracyrtus kovalevi, the latter is formally transferred to Archocyrtus (as A. kovalevi comb. nov.). Two new genera and three new species of fossil spider flies in Baltic amber are described. Cyrtinella flavinigra gen. et sp. nov. is placed in Acrocerinae, while Hoffeinsomyia leptogaster gen. et sp. nov. and Prophilopota variegata sp. nov. are included in Philopotinae. Cyrtinella is very distinctive and closely related to the Palaearctic genus Cyrtus based on the position of antennae and wing venation. Hoffeinsomyia leptogaster can be easily differentiated from all other extant and fossil Philopotinae by the presence of a cell m3 and labellate mouthparts. Prophilopota variegata is the second species described in the genus, which can be easily distinguished from P. succinea by the absence of maxillary palpi and the more complete wing venation. Diagnoses and a dichotomous key to all fossil taxa of Acroceridae are provided. http://zoobank.org/urn:lsid:zoobank.org:pub:8F2239D3-5B76-4D56-A266-8F5CDDD5CC92