ABSTRACT. Despite decades of research on Ranchman's tiger moth (Platyprepia virginalis), little is known about the behavior and ecology of the adult life stage. To address this knowledge gap, we conducted surveys to quantify the spatial distribution of moths, and conducted laboratory and field oviposition assays as well as a field oviposition survey. We found that P. virginalis exhibits hilltopping behavior, a mate-locating strategy where individuals congregate on hilltops to increase the likelihood of sexual encounters. This behavior is common across many insect orders, but there are few examples of moths exhibiting this behavior. We found no evidence supporting our hypothesis that bush lupine (Lupinus arboreus), the primary larval hostplant within our study site, is the preferred oviposition hostplant. The opportunistic discovery of egg clutches on seaside daisy plants (Erigeron glaucus) led us to conduct a no-choice larval feeding assay to determine its suitability as a hostplant. We found that larvae ...