A variety of diffusion and convection-diffusion models were fit to field mark-recapture data for female cabbage root flies (Delia brassicae Bouchè). Hawkes' hypothesis that anemotaxis is key to Delia's discovery of Brassica crops was tested by comparing the performance of different models. Whereas models lacking a convection term totally failed, models with a convection term explained 39–44%of the observed variance in Delia recapture density. The direction of the best-fit convection vector was toward Brassica and in almost perfect opposition to the prevailing winds. This suggests that Delia fly upwind in the presence of Brassica odors. The application of diffusion-convection models to insect dispersal is discussed in general, with special emphasis on parameter identification methods. These methods (new to the biological literature) allow one to find realistic dispersal models that describe field mark-recapture data.