Cephalic anatomy of minute underground larvae of Dilar (Dilaridae)-conflicting phylogenetic signal in Neuroptera and evolutionary transformations in the larval stages.

Dilaridae are a distinctive and phylogenetically ambiguous neuropteran family. The anatomy of immature stages was largely unknown so far. We examined the 1st instar larvae of Dilar montanus in detail and present results of live observations for the first time. The minute, cryptic larvae display features correlated with their underground lifestyle, for instance a strongly flattened head, stout antennae, eyelessness, and burrowing forelegs. In contrast to molecular data, several characters suggest a 'dilarid clade' combining Dilaridae with Mantispoidea, for instance a very thin and curved or reduced tentorial bridge, straight and subparallel sucking stylets, and an elongated postmentum. We found intrinsic antennal muscles and Johnston's organ, the first record of these structures in holometabolous larvae. This proves that the first two larval antennomeres are homologous with the scapus and pedicellus. The described characters are discussed and analyzed with an updated matrix of neuropteran larval characters. Alternative scenarios of character evolution are presented. Additionally, we show how the 1st instar larvae move and feed in the substrate, and also a high resolution video record of the function of the elongate tubular ovipositor and the egg-laying behavior in an adult female under natural conditions. This article is protected by copyright. All rights reserved.