Acts as a homeotic selector gene controlling antennal and mandibular segment identity. EMS has two different spatial patterns of expression during embryogenesis. The EMS head-specific expression pattern initiates prior to cellular blastoderm and continues only until early germ-band extension. The EMS metameric expression pattern initiates after gastrulation and is expressed in the lateral neuroblasts, in ectodermal cells at the anterior lateral borders of each segment, and in the Filzkoerper primordia. The sequence shown is that of strain canton S. Belongs to the EMX homeobox family.