Abstract A clonal analysis of wild-type and aristapedia eye-antenna discs has shown that both discs are subdivided into anterior and posterior compartments. However, the spatial order of the anterior and posterior compartments is reversed in the adult, so that the posterior compartment is at the extreme anterior tip of the fly. The mutation aristapedia transforms both the anterior and the posterior antennal compartments into anterior and posterior leg compartments, respectively. The anteroposterior segregation is established in the eye-antenna disc during the larval period. This contrasts with other discs (leg, wing, proboscis) where the same segregation is established around blastoderm. The engrailed gene is involved in the segregation; some of the mutations in engrailed transform the posterior antennal compartment into a partial mirror image of the anterior one.