Recently, the study of achaete-scute (AS-C) homologues has contributed enormously to understanding of gene duplication and function evolution, particularly in Diptera. We identified four AS-C homologue genes in the silkworm, Bombyx mori, referred to as BmASH, BmASH2, BmASH3, and Bmase. The complex displayed tandem array structure in the genome. Analysis of spatial expression profiles showed that they all were expressed in obviously higher levels in wing disc than in other tissues, suggesting that they might play important roles in the development of the wing. Furthermore, we found that their expression profiles in the wing discs were mostly correlated with the development of the scales, especially the BmASH gene. RNA interference results further indicated that BmASH was necessary for scale formation in silkworm wing.