Air temperature and relative humidity effects on behavioral activity of blacklegged tick (Acari: Ixodidae) nymphs in New Jersey.

Air-temperature and relative humidity data were used to explain variation in behavioral activity of Ixodes scapularis Say nymphs. We estimated behavioral activity as the residual variation in drag-sample data after seasonal changes in population density were removed by regression. The seasonal decline in drag samples between June and August 1995 on field plots at Morristown National Historical Park, NJ, can be described by a simple negative exponential function. Residuals around a fitted exponential were significantly correlated with temperature and with relative humidity measured at the leaf-litter surface, and explained 34 and 44% of the variance, respectively. Multiple regression on temperature and relative humidity explained 51% of the variance. These regressions estimated the explanatory power of microclimate, independent of seasonal correlations, and might provide a basis for day-to-day prediction of human exposure to Lyme disease.