en mutant embryos lack all Keilin's organs. However en^X49/en¹⁰ heterozygotes have about one Keilin's sensory hair per embryo and do not show a pair-rule phenotype. en¹⁰/en¹⁰, en¹⁰/en^X49 and en¹⁰/en⁷ embryos grew in in vivo culture, producing implants containing imaginal discs and all larval tissues. Metamorphosed implants were often characteristic of eye-antenna discs, or sometimes thoracic discs. Tissues derived from the thoracic discs contained only anterior structures.

en¹⁰/en¹ flies have wild-type shape wings and a wild-type scutellum. Vein III appears thickened and tends to have a posteriorwards bulge about halfway along its length. The anterior crossvein (ACV) is often reduced or absent. Small plexae of vein tissue tend to occur close to the ACV and the posterior crossvein. Vein IV is frequently interrupted and often carries campaniform sensilla. Bristles are occasionally seen in the posterior row, but they never have the characteristics of the middle triple row.