Fig. 9. Histamine is reduced in the heads of four fly species with white eyes. These are: Sarcophaga spp., combined data from two species that compare S. bullata (wild-type) with S. barbata (mutant ivory, with white eyes); Calliphora erythrocephala (wild-type) with chalky (white eye); Musca domestica (wild-type and white-eyed); and Drosophila melanogaster, white null mutant and O-R wild-type.