EVIDENCE FOR KAIROMONAL INFLUENCE ON SELECTION OF HOST-AMBUSHING SITES BY ADULT IXODES-SCAPULARIS (ACARI, IXODIDAE)

Unfed adult blacklegged ticks Ixodes scapularis Say, were tested under laboratory conditions for behavioral responses to substances rubbed from external glands on legs of white-tailed deer, Odocoileus virginianus (Zimmermann). In replicated trials, significantly more female ticks became stationary on portions of vertical glass tubing rubbed with the tarsal gland substances of both bucks and does than on nontreated tubing. This behavior, apparently an arrestant response, was infrequent among males. White-tailed deer urinate upon their tarsal glands, and doe urine also produced an arrestant response among female ticks. Metatarsal gland secretions of bucks elicited no arrestant response in either male or female I. scapularis, but doe metatarsal gland secretions elicited low-level positive responses from both sexes. A los-level arrestant response also was exhibited by females to secretions from the interdigital glands of bucks. In a second bioassay, three times as many females came to rest on the terminal ends of vertical glass rods whose bases were treated with secretions from buck interdigital glands than on rods with nontreated bases. This suggests that interdigital gland secretion influences blacklegged tick climbing behavior. Substances produced by or associated with the leg glands of O. virginianus may therefore serve as kairomones for host-seeking adult I. scapularis; interdigital gland secretions on soil or leaf litter may signal active deer trails, and tarsal gland substances may denote portions of vegetation contacted previously by white-tailed deer. In nature, use of these chemical cues by host-seeking adult I. scapularis may increase the probability of acquiring a suitable host.