Comparison of known and suspected pheromonal constituents in males of the African ticks,Amblyomma hebraeum Koch andAmblyomma variegatum (Fabricius)

Three low molecular weight compounds were found in hexane: diethyl ether extracts of fed males of the African ticks,Amblyomma variegatum (tropical bont tick) andA. hebraeum (bont tick), namely,o-nitrophenol, methyl salicylate and 2,6-dichlorophenol. These same compounds were also found in a rinse of fedA. variegatum males, but were absent or present in only trace amounts in a rinse of fedA. hebraeum males.o-Nitrophenol and methyl salicylate were present in much higher concentrations (i.e., amounts/tick) inA. variegatum than inA. hebraeum. 2,6-Dichlorophenol was also more abundant inA. variegatum than inA. hebraeum, but the differences were not as great as with the former two compounds. Extraction in hexane over a 3-week period revealed four additional compounds, benzaldehyde, benzyl alcohol, benzothiazole and nonanoic acid. The first three compounds were found in males of both species; nonanoic acid was found only inA. hebraeum males. Published reports consistently show strong attraction byo-nitrophenol and methyl salicylate for both sexes of the two bont tick species; 2,6-dichlorophenol and benzaldehyde have been reported to be attractive to both sexes ofA. hebraeum. The possible roles of these compounds, as well as others occasionally reported fromA. hebraeum andA. variegatum, as components of the aggregation/attachment pheromone or other pheromones is discussed.Supported by Cooperative Agreement No. AFR-0435A-00-9084-00 with the U.S. Agency for International Development to the Department of Infectious Diseases, College of Veterinary Medicine, University of Florida, Gainesville, FL.