INNATE CONTROL OF LOCAL SEARCH BEHAVIOR IN THE HOUSE-FLY, MUSCA-DOMESTICA

The genetic basis of variation in local searching behaviour in the hou se fly, Musca domestica L., was examined by estimating the heritabilit y of locomotory parameters using parent-offspring regressions. Pathway s of adult flies were videotaped for 3 min after ingestion of a 1 mul drop of 0.25 M sucrose in a 75 cm diameter circular arena with minimal external cues. Locomotory variables computed from digitized walking p athways, including locomotory rate, turning rates per unit of distance and time, turn bias, number of stops, and stop duration, were signifi cantly heritable, but heritabilities (additive genetic variance divide d-by total phenotypic variance) was generally low (<0.25). Phenotypic variance in search parameters increased with time since ingestion of t he sucrose drop, but heritabilities were highest when only the first 3 0 s of the searching bout were examined, and declined as longer period s were considered. Significant genetic correlations among search param eters suggest that many of these characters are influenced pleiotropic ally by the same genes or closely linked genes. However, some aspects of local search were inherited independently (e.g. stop duration and l ocomotory rate). The independence of controlling mechanisms was suppor ted by observed differences between genetic and environmental correlat ions. This genetic independence could enhance the likelihood of approp riate population responses to temporally or spatially changing selecti ve forces.