Fig.4. Effect of selection treatment and time on urea food on urea uptake. After rearing on normal food, larvae were switched to 300mmoll^-1 urea food or normal food. The zero time point represents larvae switched to normal food, who thus had no exposure to urea. Hemolymph urea concentrations increase with increasing time on urea food. The rate of urea uptake is significantly greater in the controls than in the selected larvae (8.98mmoll^-1h^-1 versus 7.12mmoll^-1h^-1, respectively; values are means ± 1 S.D., N=5, ANCOVA, P<0.029).