An ectopic macrochaeta in the middle of a compound eye of a field-collected anthomyiid fly.

Recording and describing animal 'monsters' collected in the field can still contribute to progress in developmental biology despite the uncontrolled conditions the specimen experienced throughout development. Comparison with model organisms and a sound phylogenetic analysis may offer a tentative explanation for the underlying developmental mechanism and suggest new targets for experimental studies. We describe a female specimen of the anthomyiid fly Hydrophoria sp. with an ectopic macrochaeta in the left eye and suggest tentative interpretations, including one in terms of a local expression, or derepression, of a proneural gene. The anthomyiid lineage has been estimated to have split ca. 65 million years ago from the dipteran clade containing Drosophila and ca. 140 million years ago from the clade containing Megaselia.