The courtship index of naive ss^a40a males is lower than that of CantonS controls.

Mutant males show can form immediate memory in a courtship suppression paradigm (CCSP), with the courtship index being reduced immediately after conditioning, but have a significant reduction in the learning index one day after training compared to immediately after training, indicating a defect in long-term memory.

Segmentation of hemizygotes is temperature sensitive. Hemizygotes exhibit incomplete tarsal segmentation.

Homozygotes and ss^a40a/ss^aP88 flies show transformation of the arista to distal mesothoracic tarsus. Expressivity of the phenotype is higher in ss^a40a/ss^aP88 flies than in ss^a40a homozygotes. The expressivity of the phenotype decreases with increasing temperature in ss^aB/ss^a40a flies. A high proportion of homozygous or ss^a40a/ss^aP88 flies produce an ectopic tarsal response to chemical stimulation at 25^oC. Homozygous and ss^a40a/ss^aP88 flies can often fly.

cold-sensitive phenotype normal in flies raised at 29^oC; fully penetrant at 17^oC <up>mean number of tarsal segments = 2.8; incidence of tarsal claws = 1.3% as recorded by Garcia-Bellido (1968) probably in flies raised at 25^oC</up>. Phenocritical stage in first half of third instar (Grigliatti and Suzuki, 1971). Shifts from 17^oC to 29^oC early in third instar restrict transformation to base of arista; distal extent of transformation increases as shift is effected later in development (Grigliatti and Suzuki). Opposite response to temperature for antennal transformation but not tarsal fusion reported by Mglinetz (1977). Developmental compartments demonstrated in antennal legs (Morata and Lawrence, 1979). cold-sensitive

al¹, ss^a40a has tarsal segment phenotype

al¹, ss^a40a has third segment of antenna phenotype