Canyon flies are a major nuisance pest of both humans and animals in the dry canyon areas of Southern California, where they swarm in huge numbers during early summer. Despite the large populations and annoyance these flies cause, their biology and behavior are somewhat poorly understood. Over the summer of 2006, diel female host seeking and male swarming activities were monitored and correlated with environmental conditions. In addition, both sexes were subjected to the anthrone sugar assay to determine daily sugar feeding patterns and analyzed for difference by sex and time of day. Previous research indicated a strong response to carbon dioxide, but failed to show a significant response to many common pungent fly baits. Expanding on this idea, fly response to blood and ammonia, two common attractants for host-seeking insects, were tested. The results of this study may be helpful in designing and implementing control strategies for these pestiferous flies.