Fossil evidence of social insect commensalism in the Phoridae (Insecta: Diptera)

Fossil phorid flies display various levels of morphological change that are correlated with myrmecophily (association with ants) and termitophily (association with termites) in the modern fauna. Three discrete episodes in the evolution of limuloidy, a defensive body form, are documented from Eocene Baltic amber. Extinct fossil stem-group taxa of the modern myrmecophilous genus <i>Aenigmatias</i> Meinert are described, with three new species – <i>A. longicornis</i> sp. nov., <i>A. primitivus</i> sp. nov. and <i>A. nigeroticus</i> sp. nov. – recognized and illustrated. <i>Protoplatyphora</i> Brues is synonymized with <i>Aenigmatias</i>, with its single previously described species, <i>A. tertiarius</i> (Brues), considered a new combination. <i>Chaetopleurophora bisetosa</i> Brown, 2007 is transferred to <i>Aenigmatias</i> as <i>A. bisetosus</i> (comb. nov.). An unrelated <i>Aenigmatias</i>-like fossil is described as <i>Pseudaenigmatias ctenitibia</i> gen. et sp. nov., and belongs to a modern termitophilous clade. <i>Limulomyia tyche</i> Brown, 1999 is interpreted as a separate, already highly limuloid lineage not related to either of the other two limuloid groups. A key to fossil <i>Aenigmatias</i> is given, along with a phylogenetic analysis of fossil taxa. Fossil specimens have profound implications for our knowledge of the evolution of the limuloid body form found in modern species of <i>Aenigmatias</i>. http://zoobank.org/urn:lsid:zoobank.org:pub:DE779D49-7636-4B1D-9F7D-CF3FF6D3CE97