Significant outbreaks of saddled prominent, Heterocampa guttivitta (Walker), have been recorded in northern hardwood stands throughout the northeastern United States since 1907 and were first noted in Ontario in 1938 (Martinat and Allen 1988). The insect overwinters as a pupa beneath litter, adult emergence begins in late May and peaks in mid-June, and oviposition activity ends in early July. Consequently, the major impact of defoliation usually occurs in late summer feeding. Principal hosts are sugar maple, Acer saccharum Marsh. (Aceraceae), American beech, Fagus grandifolia (Ehrh.) (Fagaceae), and yellow birch, Betula alleghaniensis Britton (Betulaceae) (Rush and Allen 1987). Two successive years of severe (>75%) defoliation of sugar maple result in significant growth loss (Bauce and Allen 1991), and heavy mortality may occur to understory sugar maple (Grimble and Newel1 1973). The quantity and sugar content of sugar maple sap are dramatically reduced the spring following heavy (>50%) defoliation (Magasi 1981; Handy 1968). Heavy to severe defoliation may cause crown dieback and defoliation and, in concert with other stresses, may initiate maple decline (Giese et al. 1964). Currently, monitoring and evaluation of saddled prominent populations must rely on egg sampling (Grimble and Kasile 1974), a time-consuming process that is inconvenient for survey personnel and landowners. A sex pheromone has not been identified for this species (nor for any other North American Notodontidae) and would be a potentially useful tool for detecting incipient outbreaks, predicting population levels, and evaluating population trends.