The Forest Insect Survey of the Maritime Provinces has been observing an outbreak of the winter moth, Operophtera brumata (Linn.), since its discovery in Nova Scotia in 1949. In addition to noting annual changes in distribution, the Survey has made population counts on 8 to 20 tagged trees of red oak, Quercus rubra L., at each of seven locations along the south shore of the Province. These trees were sampled each year to show the abundance of larvae of the winter moth and the fall cankerworm, Alsophila pometaria (Harr.). Both species are commonly found on the same trees, and their life histories are similar. The collections and subsequent rearings also showed the degree of parasitism by native or introduced species of parasites. The defoliation of the trees was estimated at the time of sampling and again at the end of the feeding period to determine the relationship between larval population and defoliation. Some of the sampling data, which were collected from 1952 to 1955, are used to develap the sequential plan of sampling described herein. Use of the plan at the sampling stations should reduce the number of samples while retaining accuracy within predetermined limits.