Larvae of Ochlerotatus thibaulti Dyar and Knab have not been reported in New York State or New England, but adult records suggest that breeding populations are present. In 2003 and 2004, larval Oc. thibaulti were collected at 3 sites upstate near the Catskill Mountain region in Lomontville, NY. This is the 1st record of Oc. thibaulti collected in New York and New England. Larvae were found in a variety of subterranean habitats within and near semipermanent woodland pools, including under hummocks and in deep and shallow depressions of upturned trees. No immatures were observed after late June. Larvae of Culiseta melanura were found in the same habitats in the early spring and later in the season after Oc. thibaulti had emerged.