The purpose of the research outlined in this proposal is to explain the behavioral, physiological, and developmental adaptations that support Ixodes baergi in a host-parasite relationship with cliff swallows. Work of a similar nature, except involving Argas cooleyi and Ornithodoros concanensis is in progress, but is nearing completion. The proposed research is divided into 5 broad phases: (1) Measuring the ability of the ticks to maintain water balance and to survive exposure to temperature extremes. (2) Determining the effects of humidity, temperature, and light on activity and aggregation. (3) Studying seasonal activity and developmental patterns, host-finding activity rhythms, and patterns of dropping off of engorged ticks. (4) Studying the host-finding behavior. (5) Field work to collect data on the ecology of 1. baergi (an effort in the field to evaluate host-finding activity will also include. A. cooleyi and O. concanensis).