Conditioning odor-shock associations in the black blowfly, Phormia regina

Discriminative classical conditioning of an olfactory avoidance response was demonstrated in the blowfly, Phormia regina. Learning indices were calculated as the fraction of flies avoiding the CS+ (conditioned stimulus paired with electric shock reinforcement) minus the fraction of flies avoiding the CS-(conditioned stimulus not paired with electric shock), averaged over two different groups of flies, in which reciprocal odors were used as the CS+. Avoidance responses to both odors presented simultaneously at a T-maze choice point yielded mean learning indices of zero for naive flies or pseudoconditioned (shock alone) or sensitized (odors alone) controls. In contrast, pairing an odor with electric shock produced a mean learning index significantly greater than zero. These results are similar to those reported for Drosophila melanogaster. Blow flies, however, showed much lower levels of associative learning than fruit flies.