is expressed as a gap gene but has no gap gene phenotype in the moth midge .

Gap genes are involved in segment determination during early development of the vinegar fly and other dipteran insects (flies, midges and mosquitoes). They are expressed in overlapping domains along the antero-posterior (A-P) axis of the blastoderm embryo. While gap domains cover the entire length of the A-P axis in there is a region in the blastoderm of the moth midge , which lacks canonical gap gene expression. Is a non-canonical gap gene functioning in this area? Here, we characterize () in . The homologue of in the flour beetle (called ) is a gap gene. We find that is expressed in the region previously reported as lacking gap gene expression. Using RNA interference, we study the interaction of with gap genes. We show that is regulated by gap genes, but only has a very subtle effect on while not affecting other gap genes at all. Moreover, cuticle phenotypes of depleted embryos do not show any gap phenotype. We conclude that is expressed and regulated like a gap gene, but does not function as a gap gene in .