Successful expression of genes transferred into distantly related species in which genetic functions have been maintained through evolution has been reported previously. In the case of the silkmoth Bombyx mori and the fruitfly Drosophila melanogaster, both of which produce chorions (eggshells), Bombyx chorion genes are correctly expressed in Drosophila despite their estimated 240-Myr phylogenetic divergence. Here we report that, although Drosophila does not produce silk, mechanisms regulating transcription have been conserved between the salivary gland of the fruitfly and the silk gland of the silkmoth larva.