Extra bristles present in homozygote at or near almost all normal bristle locations but most frequently in dorsocentral and scutellar regions. Heterozygote in some stocks occasionally shows extra bristles, especially vibrissae. Character expressed better at low temperatures and in large flies. Combinations with h and ac generally superadditive for bristle number. Resembles the original allele, both in chromosome location and bristle phenotype. RK3.