An evaluation of the major components of the cuticular washes from both male and female face flies,Musca autumnalisDe Geer, revealed that the most active component was (Z)-14-nonacosene. The activity of this component was not augmented by coadministration of the other components. Examination of several synthetic materials revealed that certain ethers inhibit this stimulant activity; for example, (Z)-14-nonacosene was not active when it was tested with methyl tetradecyl ether.