Sex Pheromone Regulation of Mating Behavior in the Tick Ornithodoros (Ornithodoros) savignyi (Audouin) (Acari: Argasidae)

Bioassays performed on Ornithodoros (Ornithodoros) savignyi (Audouin) demonstrated the presence of a female sex pheromone. Unfed adults and fed adults, after various postfeeding periods, were cross-tested. Two independent criteria were used: the percentage of positive male responses and the time elapsed before these responses. Females were least attractive when unfed and on the feeding day. Their attractiveness increased afterwards reaching the highest values 6 d after feeding (confirmed attractive, CA, females) then decreased gradually thereafter. Males were least responsive during the first 2 d after feeding and became more responsive afterwards reaching a peak 8 d after feeding (sexually active, SA, males). Unfed male responses to CA females were strong but were lower than those of SA males. The fastest responses in all bioassays were those of SA males to CA females. The maximum distance of SA male response to CA females was about 9 cm. SA males were not attracted to nymphs, CA females with sealed coxal orifice, or dead CA females. However, they responded to nymphs coated with coxal fluid collected from CA females. Nymphs and females were not attracted to CA females.