Responses of the ticks Amblyomma hebraeum and A. variegatum to known or potential components of the aggregation-attachment pheromone. IV. Attachment stimulation of nymphs.

Ten known or potential components of the aggregation-attachment pheromone (AAP) of the ticks Amblyomma hebraeum and A. variegatum, as well as a mixture of these components and extracts of prefed males of the two species, were tested as attachment stimulants for nymphs. Unfed nymphs were confined in linen bags on the ears of rabbits that had been treated with the test compounds, mixture or extracts; the numbers attached were recorded after 24 h. In A. hebraeum, attachment was induced by four compounds (2-methyl propanoic acid, methyl salicylate, o-nitrophenol and salicylaldehyde), the mixture and extracts from both species. In A. variegatum, attachment was induced by three compounds (methyl salicylate, o-nitrophenol and salicylaldehyde), the mixture and extracts from both species. Methyl salicylate and o-nitrophenol are primary components of the AAP of both A. hebraeum and A. variegatum. 2-methyl propanoic acid is a species-specific attachment stimulant for A. hebraeum. Salicylaldehyde, a phenolic compound, is not a naturally occurring AAP component. Nymphs of both species respond to fewer attachment stimulants than the adults and, as shown by their respective host ranges, are less dependent on the AAP in the regulation of attachment than the adults.