Crematogaster obscurata occurs in dry forest habitats and beach margins. Mark Deyrup recently discovered a nest in the Florida keys, where it is most likely a recent introduction. I have collected the species twice in Costa Rica, both collections from Santa Rosa National Park in the seasonally dry habitats of Guanacaste Province. One collection was made while collecting at night in second growth dry forest near the park administrative headquarters. An aggregation of workers was in a tree knot. The second collection was from Playa Naranjo, at the upper beach edge. Small necrotic spots in live stems of a small Gliricidia sepium tree (Fabaceae) contained aggregations of workers only, with no brood or sexuals. The collection was made in the late afternoon, and the workers were not foraging. Even when the cavities were disturbed, the workers remained quiescent, appressed to the walls. The types of Wheeler's agnita were collected in hollow twigs, and workers have been twice intercepted in U.S. quarantine stations, in both cases in Oncidium orchids from Guatemala.