Food-search behavior and its relation to the central excitatory state in the genetic analysis of the blow fly Phormia regina.

Dethier (1957) described an aspect of food-search behavior in Phormia regina as the blow fly dance. A hungry fly walks in relatively straight lines with its proboscis retracted until it encounters food (sucrose). After ingesting even a small amount of sucrose, the fly begins making frequent, tight turns, flexes its front tarsi to bring more chemosensory hairs into contact with the substrate and repeatedly extends and retracts its proboscis. Like the central excitatory state (CES), which causes an increase in proboscis extensions to water when a fly is stimulated with sucrose, the dance lasts longer in hungrier flies or with higher sucrose concentrations. It was considered that dance behavior might be an ethologically relevant manifestation of CES. In order to test this hypothesis, dance duration in lines selected for high- and low-CES levels was measured. As predicted, flies from the high-CES line danced longer than those from the low-CES line, and the CES-dance correlation in individual flies was high. This phenotypic correlation disappeared in the F2 generation of a cross between the high- and low-CES lines, a result indicating that the observed variations in CES and dance duration were not caused by the same set of genes. Further characterization of the underlying genetic system showed that several linked autosomal genes with digenic epistatic interactions and a complex pattern of maternal inheritance were responsible for the difference in dance durations between the high- and low-CES lines.