Role of genital sex pheromones in Amblyomma americanum and A. maculatum (Acari: Ixodidae).

Amblyomma americanum and A. maculatum were studied to determine if genital sex pheromones were present, as reported in Dermacentor species. Chemical analysis of methanol extracts of the anterior reproductive tracts (source of the genital sex pheromone) of A. americanum and A. maculatum confirmed the presence of the same fatty acids that act as components of the genital sex pheromone in Dermacentor variabilis and D. andersoni. In both Amblyomma species, removal of the anterior reproductive-tract of fed females eliminated the male copulatory response. For A. americanum, use of anterior reproductive tract extracts made with water, methanol, ether and hexane elicited significant probing and copulatory responses by conspecific males. However, in A. maculatum, use of anterior reproductive-tract extracts made with water, methanol, ether, chloroform:methanol (4:1), hexane and pentane did not restore mating response by males. Treatment with known components of Dermacentor genital sex pheromones elicited weak but significant responses in A. americanum, but did not restore male mating responses in A. maculatum. These results indicate that genital sex pheromones exist in A. americanum and are not restricted to the genus Dermacentor. Characteristics of the Amblyomma genital sex pheromone, however, do differ considerably from those in Dermacentor. No genital sex pheromone was present in A. maculatum.