Crepuscular movement of the leafhopper vector of X-disease,Paraphlepsius irroratus(Say), between orchard groundcover and fruit tree foliage and back was monitored by light-trapping and sweeping within a sour cherry orchard. The adult leafhoppers spent the day within orchard groundcover, and at twilight they moved into fruit tree foliage. There was no significant difference in this diurnal behavior between the two adult generations. Leafhopper density found in several within-orchard subhabitats (i.e., groundcover, sour cherry foliage, sweet cherry foliage) changed significantly over a 24-h period. The active crepuscular mass flight into the trees in the evening was contrasted to the passive movement back into the orchard groundcover the following morning.