Duration and regulation of the developmental cycle of Ixodes dammini (Acari: Ixodidae).

To determine how long the various developmental stages of the deer tick (Ixodes dammini Spielman, Clifford, Piesman & Corwin) survive in nature and to establish the interval between blood feeding and ecdysis or oviposition as well as subsequent larval eclosion, we observed ticks confined in the field. Unless adults feed during their first season (fall through spring) of activity, they die and do not survive the summer. Nonfed nymphs survive through two seasons (May through August) of feeding activity such that annual cohorts overlap. Nonfed larvae survive less than one year, and because they hatch toward the end of the summer, cohorts of this developmental stage do not overlap. Larvae that feed before September molt promptly and overwinter as nymphs; those that feed later overwinter engorged and ecdyse during the following spring. Fed nymphs fail to survive the winter, and thus must feed before late summer. They develop to the adult stage in the same year in which they feed. Regardless of time of feeding, females lay eggs in early summer, and the resulting larvae synchronously eclose late in that season. Although the cycle of this tick can be completed in nature in two years, it may extend to four years when hosts are relatively scarce. The seasonal inversion of larvae and nymphs appears to be regulated by physiological mechanisms and by host abundance.