Technical Abstract: Volatile signals mediate many multitrophic interactions, some due to coevolution and others due to eavesdropping, but the role of specific concentrations and ratios has been controversial and difficult to test due to methodological limitations. We investigated the role of ratio and concentration using a previously identified seven-component blend essential for host location by the specialist grape berry moth (GBM). In flight-tunnel assays, doubling the amount of six compounds singly or mimicking the ratio changes caused by Japanese beetle foliar feeding significantly reduced GBM female upwind flight. The reduction was similar at high and low doses. Although our results indicate the importance of ratios of some compounds in providing specificity, GBM was also able to accommodate significant variation in the ratio of some compounds as well as the concentration of the overall mixture. Such plasticity may be critical for phytophagous insects to successfully eavesdrop on variable host plant volatile signals.