Phoridae (Diptera) mating behaviour: identification of general patterns, exceptions and the use of sexually dimorphic structures based on vast citizen science data

Phoridae mating habits, like many aspects of this diverse family of flies, are poorly known. In this study, we compiled data from the literature and online photo and video-sharing platforms to understand general patterns of Phoridae reproductive behaviour. The photos illustrate the mating habits of 17 phorid genera of its two largest subfamilies, including genera that were previously known exclusively from preserved specimens in collections. We identified a general mating position for the family in which the male is behind and partially over the female, reaching with his forelegs the dorsal face of her wings while the female generally has her wings straight, resting over the abdomen. Some genera show remarkable exceptions to this position, including the male projected anteriorly over the female, the male being lifted high by the female, and the male under the female wings. Sexually dimorphic features of different genera are shown to be in contact during mating, possibly performing a stimulatory function. New cases of females displaying to males are also presented. Sexual selection theories that could explain the male–female interactions illustrated and the diversification of sexually dimorphic structures are also discussed. We believe that this compilation provides a general context for discussing Phoridae mating habits, and we hope this work leads to the development of new studies examining sexual selection in phorids.