Alarm pheromones are released when a bee stings another animal, and attract other bees to the location and causes the other bees to behave defensively, i.e. sting or charge. Upon attack, honey bees produce an alarm pheromone that elicits different responses depending upon the setting. Predation at food sources can elicit alarm. Identifying and testing different chemical components of alarm pheromone in honey bees is important for understanding what elicits avoidance following attacks at natural food. Apis dorsata, giant Asian honey bee, is widespread throughout Asia and is an important pollinator of crops and native plants. It is sympatric with two other native Apis species with which it shares alarm pheromone components. Therefore, giant Asian honey bee is a good species to study because little is known about its behavioral responses to alarm pheromone. 

     Prof. TAN Ken and his team of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to understand how A. dorsata alarm pheromone would affect conspecific foraging behavior, and to determine which chemical components have the strongest effect on conspecific foragers.

    Using solid phase micro-extraction (SPME) fibers, the researchers collected alarm pheromones from the airspace around bees captured in vials. A choice between two inflorescences, one with the treatment odor and the other with a control, was offered to foragers. They tested the effects of natural alarm pheromone, individual pheromone components that they chemically identified, and a synthetic mixture of these components on A. dorsata foraging at C. haematocephala inflorescences.

Apis dorsata foragers were found to avoid their alarm pheromone when this was presented at a food source, a situation that occurs when foraging bees are attacked by predators.

 Using gas chromatography–mass spectrometry (GC–MS) analysis, the researchers identified eight chemical components in the alarm pheromone, of which three components (1- octanol, decanal and gamma-octanoic lactone) have not previously been identified in this species. It showed that gamma-octanoic lactone, isopentyl acetate and (E)-2-decen-1-yl acetate were active compounds and acted like natural alarm pheromone. Of all the compounds tested, gamma-octanoic lactone appeared to be the most effective.

It indicated that alarm pheromones evolved primarily in the context of colony defence, not for warning foragers at a food source. However, even if the primary benefit of alarm pheromone signal production is colony defense, foragers from the same colony, other colonies of the same species, and even different species can benefit from sensing and using this information. Thus the simple, reflexive and reliable response of an attacked bee producing alarm pheromone, regardless of context, has broader implications for information flow.