Fig. 1. da dominantly enhances the P[sev-wg^ts] bristle phenotype. Scanning electron micrographs of adult fly heads. P[sev-wg^ts]/+ flies reared at 25°C (A) or 17.6°C (B). P[sev-wg^ts]/da^11B6 (C) and P[sev-wg^ts]/da³ (D) flies reared at 17.6°C. P[sev-wg^ts]/+ flies reared at the lower temperature had about 150 bristles/eye (compared to approximately 600 observed at 25°C) grouped in the dorsal third of the eye (large arrows) with a few bristles in the ventral half (small arrows in B). When heterozygous for strong da alleles, bristle number was reduced to 10-25 bristles/eye, and no bristles were seen in the ventral half of the eye.