Microclimate and habitat in relation to Ixodes scapularis (Acari : Ixodidae) populations on Long Point, Ontario, Canada

The impact of microclimate and density of hosts for adult ticks on the dens ity of Ixodes scapularis Say was evaluated within 4 habitats on Long Point, Ontario, from 1989-1992. During the period from May to September, mean wee kly vapor pressure deficits were greater within the oak savannah and cotton wood dune habitats than at the maple forest and white pine habitats, which were similar. Vapor pressure deficit was likely the major factor affecting the survivorship of eggs and immature ticks in these habitats. Based on dra g sampling, I. scapularis adults demonstrated peak activity in April and Oc tober of each year. The mean number of I. scapularis adults collected by dr agging during the fall or in the spring did not differ significantly within each habitat. The mean number of adults collected also did not differ amon g tick cohorts within each habitat; however, significantly more adults were collected within the maple forest than in the white pine habitat. The mean number of I. scapularis adults per white-tailed deer, Odocoileus virginian us (Zimmerman), increased from 1989 to 1991 and then decreased in 1992. Sig nificantly more adult I. scapularis infested deer were observed in 1990 tha n in 1989. Removal of deer in 1989 and 1990 resulted in a calculated decrea se of >100,000 fed female ticks. Although seasonal variation in microclimat e within habitats was closely linked with tick survival and partly explains the differences in abundance of I. scapularis among habitats on Long Point , habitat utilization by deer was also a primary factor governing the local abundance of I. scapularis populations.