The goal of this project is two-fold. First, we use tools from microeconomics to characterize the choices of wild type Drosophila larvae as they tradeoff goods (dark and food) in a decision-making assay. We model these choices using a utility function that allows for complementarity between the two goods. Second, we look at how these decisions are affected by genetic mutations. Drosophila larvae have an extensive genetic toolbox that allows us to investigate the effects of targeted mutations. We first assess the degree to which decisions depart from the levels of economic rationality found in wild type larvae. For larvae making consistent decisions, we investigate whether there are changes in the degree of complementarity between the two goods in order to identify mutations that affect how goods are traded off against each other.