We examined the presence of the exotic weevil Rhinocyllus conicus Fröelich on native thistles at high elevations in the Rocky Mountains of Colorado. We tested whether the distribution of R. conicus was related to elevation by performing 2 separate studies. First, transects along an elevation gradient were sampled in Rocky Mountain National Park and presence/absence of R. conicus was scored to infer relationships between environmental variables and weevil occurrence. Second, an experiment was conducted on Niwot Ridge to determine whether weevils were able to complete their reproductive cycle and overwinter at an elevation where they do not currently exist. Results of a logistic regression indicated that R. conicus presence was negatively correlated with elevation. In addition, weevils successfully reproduced at tree line, but climatic limitations suppressed their ongoing presence at this site. The ability of the weevils to utilize native thistles at tree line was unknown prior to this experiment, and our results suggest that within the context of climate warming, the range of R. conicus could expand to include more native alpine thistles in North America.