Substrate-borne vibrations produced by adults of the treehopper Ennya chrysura Fairmaire (Hemiptera: Membracidae) on their host plant are described. Of eight different signals, five were produced by males, two by females, and one by both sexes. Possible functions are proposed according to the contexts in which signals were produced. As in other treehopper species, some vibrations were part of the courtship and probably also mate finding. Both sexes also produced signals when contacted by another individual. Females produced a drumming signal when contacted by a male or female and when rejecting a courting male; this signal was associated with aggressive behavior. Males produced a siren signal when contacted by a male or female and during certain portions of courtship songs of other males on the same plant. This signal was not associated with aggressive behavior and may serve to jam other males’ songs. This possible function has not been noted previously in any species that uses substrate-borne communication.