Discovery of 3-methyl-2-buten-1-yl acetate, a new alarm component in the sting apparatus of Africanized honeybees.

We analyzed the alarm pheromone components from five colonies of Africanized honeybees and three colonies of European honeybees collected in Mexico. Analyses revealed a novel alarm pheromone component that was only present in appreciable quantities in the Africanized bee samples. Analysis of the mass spectrum and subsequent synthesis confirmed that this compound is 3-methyl-2-buten-1-yl acetate (3M2BA), an unsaturated derivative of IPA. In Africanized honeybees, sampling from stings of guards showed that 3M2BA was present at levels of 0-38% the amount of isoamyl acetate (IPA). Behavioral assays from three colonies each of Africanized and European bees showed that 3M2BA recruited worker bees from hives of both Africanized bees and European bees at least as efficiently as isopentyl acetate IPA, a compound widely reported to have the highest activity for releasing alarm and stinging behavior in honeybees. However, a mixture of of 3M2BA and IPA (1:2) recruited bees more efficiently than either of the compounds alone. None of the compounds differed in their efficacy for inducing bees to pursue the observers.