Hemizygotes and transheterozygotes with stout4 show defects surrounding the dorsal sac. Dorsal bridge is diffuse and occasionally unfused. Strands of sclerotic material are strung out from the anterior vertical plate and ventral side of the dorsal bridge. The H-piece lateral arm is bifurcated and the crossbar widened or broken. Mouth hooks are of normal length but are thin and the bases are often reduced. Third thoracic denticle belt is narrowed. This phenotype resembles that of EcR mutants. Heterozygous adults show thickened arista, arced wings and one or more kinked macrochaetae. When the mutant males carry two copies of the wild type locus, for example using Dp(1;3)sn13a1 or Dp(1;Y)ct+y+, males are sterile.
stoutTA181/stout[+] is an enhancer of partially lethal - majority die phenotype of Dfd13/Dfd3
Allele may be neomorphic or antimorphic.