Unraveling the evolution of the spider flies (Diptera, Acroceridae): insights from morphology, DNA and fossils

Spider flies (Diptera, Acroceridae) are some of the most striking insects found in both temperate and tropical regions of the world. It comprises a morphologically heterogeneous assemblage of taxa that is seldomly sampled in entomological collections. Many species are extremely rare, while some are abundant and important pollinators in certain ecosystems. Larvae are obligate endoparasitoids of spiders, with a highly mobile first instar larva that is responsible for actively finding and entering a spider host. A total-evidence phylogeny of Acroceridae is presented, based on both morphological and DNA sequence data, including fossil taxa as terminals in estimates of relationship and divergence time. The evolution of the spider flies is discussed in a temporal and spatial context, including host use, homoplastic morphological reductionism and considerations of the likely sister group to the family. An overview of the systematics and classification of Acroceridae is presented, with indications of future directions and perspectives, including a cybertaxonomic monograph and interactive keys.