We have characterized the abdominal-A locus in a Hymenopteran, the ant Myrmica rubra. The sequence of the homeotic domain of the Abdominal-A family of orthologous genes is known for a fairly large number of insects but the complete sequence of the Abdominal-A protein, is known only for a few. The two proteins of Drosophila melanogaster and Tribolium castaneum differ markedly outside the homeodomain. A comparison of the ant Abdominal-A protein sequences with those of these two insects shows that the ant and beetle sequences are very similar all along the length of the protein. The fruit fly has diverged considerably and equally from the other two insects. This divergence reflects different rates of evolution of the protein in different lineages.