Hymenoptera is one of the orders showing conspicuous sexual dimorphism. In terms of the haplodiploid genetic systems, these sexual differences should be derived from genomic quantities. In this study, to elucidate the molecular basis underlying the sexual dimorphism, we focused on the ponerine ant Diacamma sp. in which the sexual differences of body color are considerable.

In this species, females have black cuticle, while males have red one. First, in order to confirm the ultrastructural differences in the sex-specific pigmentation, histological sections of adult cuticles were observed by TEM. Next, in order to compare the pigmentation processes between sexes in a pupal stage, these processes were observed using a binocular microscope. These observations revealed that the timings of pigmentation and the compositions of pigments were different between sexes.

To establish the molecular basis, six orthologs of Drosophila pigmentation genes were cloned and then the quantitative analyses of gene expression levels were performed. Results suggested that yellow, ebony and tan contribute to the sex-specific pigmentation. Based on the results, we discussed the gene regulatory networks for the sex-specific pigmentation.