The six-legged larvae are active July-September and can be found in moist leaf litter. Larvae hatch nearly pathogen-free from eggs (only Borrelia miyamotoi is known to infect blacklegged tick larvae), and remain in the leaf litter where they will attach to nearly any small, medium or large-sized mammal and many species of birds. Preferred hosts are white-footed mice.
Adult males and females are active October-May, as long as the daytime temperature remains above freezing. Preferring larger hosts, such as deer, adult blacklegged ticks can be found questing about knee-high on the tips of branches of low growing shrubs. Adult females readily attack humans and pets.