Defensive response variation among Apis mellifera linnaeus colonies

Honey bees (Apis mellifera) defend their colonies and food reserves against intruders primarily through stinging behaviour. However, this defensive behaviour is often considered a limiting factor for the broader adoption of beekeeping practices. To initiate a breeding program aimed at developing less defensive honey bee strains, 100 colonies were screened for their response to external stimuli. The defensive behaviour of the colonies was assessed through a colony-level assay involving the application of 100 μl of alarm pheromone (isopentyl acetate, 98%) to suede leather wrapped around a rubber ball. This ball was then oscillated in front of the colony entrance to provoke a defensive response. Three key parameters were measured: (1) the mean number of stings per minute, (2) the time taken for the first sting to occur, and (3) the number of bees recruited for defense per minute. These parameters showed considerable variation across the colonies, with the mean number of stings per minute ranging from 1.33 to 22.67, the time to the first sting ranging from 3.67 to 23.00 seconds, and the number of bees recruited for defense varying from 3.67 to 41.67 per minute. To quantify the overall defensive response of each colony, a five-point scale was applied to each of the three parameters (with 1 indicating the most aggressive behaviour and 5 indicating the gentlest). The cumulative scores for the three parameters were summed to assess the colonies’ overall defensive tendencies. Results revealed that 50% of the screened colonies received cumulative scores ranging from 10 to 12, indicating moderate defensiveness. In contrast, 34% of the colonies scored between 7 and 9, while 10% of the colonies were classified as least defensive, with scores ranging from 13 to 15. Only 6% of the colonies exhibited the highest level of defensiveness, scoring between 4 and 6. A correlation analysis indicated that the number of stings per minute was positively correlated with the number of bees recruited for defense, while it was inversely correlated with the time taken for the first sting. These findings highlight the variation in defensive behaviour across colonies and highlights the potential for selective breeding of less defensive strains. Nonetheless, further efforts are necessary to refine breeding strategies that incorporate the gentler colonies, ultimately contributing to the development of a less defensive honey bee stock for beekeeping programs.