Pheromone-induced aggregation of ixodid ticks before host contact.

The presence of a pre-feeding aggregation pheromone was demonstrated in the species Dermacentor variabilis, Dermacentor andersoni, Dermacentor parumapertus, Amblyomma americanum and Haemaphysalis leporispalustris by assay within a petri dish. However, Amblyomma maculatum and Amblyomma cajennense did not aggregate in the sector containing discs of presumed pheromone within the hour period. D. andersoni and A. americanum recognized each other's pheromone and A. americanum recognized that of H. leporispalustris. Preliminary experiments with guanine and hemin as possible aggregating factors have thus far given inconsistent results.