The winter moth is an invasive pest found in New England that causes substantial amounts of defoliation to a variety of deciduous trees. To control the outbreak population of winter moths, the tachinid parasitoid Cyzenis albicans, (Diptera: Tachinidae) has been introduced as a biological control agent. The flies lay their eggs on partially defoliated leaves, and are then consumed by the winter moth larvae. Once winter moth pupate the C. albicans begin to develop inside the body of the winter moth and eventually kill their host. Estimates of percent parasitism by C. albicans are made by collecting infected and uninfected larvae from particular tree species, especially oaks and maples. In the following experiment I showed that parasitism by C. albicans varies between tree species and at different heights in tree canopy. My experiments show that such collections should be made from a variety of tree species and canopy heights to more accurately determine the percent parasitism of a given location.