Two larval foraging strategies in Drosophila melanogaster were identified, "rover" and "sitter." "Rovers" traverse a large area while feeding whereas "sitters" cover a small area. The difference between "rovers" and "sitters" was analyzed genetically by chromosomal substitutions between isogenic stocks. Differences in larval locomotor behavior ("crawling behavior") can be attributed to the second chromosome, the "rover" strategy being dominant over the "sitter" strategy. Differences in feeding rate ("shoveling behavior") are affected additively by both the second and third chromosomes. Natural populations of Drosophila larvae were sampled three times over a 2-month period; "rovers" and "sitters" were at constant frequencies in these populations. The two foraging strategies are discussed in the light of resource utilization in environments where food is distributed continuously or discontinuously.