Scratching for food: an original feeding behavior in an African flower breeding Drosophila.

Drosophila suma is a flower breeding species widespread in the Afrotropical region. We describe an original and so far unique feeding behavior in that species. Strong black spines on the fore tarsus of both sexes are used for scratching the surface of the petals: the juice pouring out from the scratched cells is immediately ingested and this might be the only source of food. D. suma has been investigated on two kinds of flowers, Ipomoea and Crinum. In spite of the very different shape and color of these flowers, the feeding behavior of the flies is the same. Various morphological and anatomical adaptations are described, especially those related to laying a few very big eggs. The taxonomic position of D. suma has long remained and still is elusive. Further taxonomic and phylogenetic investigations would thus be needed to understand how adaptation to flower breeding has evolved.