Evidence of an assembly pheromone in the black-legged deer tick, Ixodes scapularis

The responses of Irodes scapularis (Acari: Ixodidae) nymphs and adults to extracts of cast larval skins were tested in a Petri dish bioassay. Assembly was elicited in nymphs and adults in the presence of skins, exudate from ticks, and filter paper exposed to ticks compared to untreated controls. Assembly was noted by 1 hr after exposure with little change between 1 and 24 hr. The assembly response increased in the presence of an increased number of skins. Similar assembly was elicited in nymphs and adults in the presence of cast larval skins and a saline (0.95% NaCl) skin extract. Methanol and hexane extracts were not attractive. When chemical standards were tested against nymphs, they responded to guanine, uric acid, hypoxanthine, xanthine, inosine, and hematin. Adults were tested against guanine, inosine, and xanthine, and all elicited significant assembly. Responses of nymphs increased significantly with increase in dose of uric acid and guanine. Responses of nymphs to a mixture of guanine, xanthine, and adenine (25:1:1 ratio) were similar to responses to cast skins. This study provides the first evidence of an assembly pheromone in I. scapularis.