A Few Critical Cuticular Hydrocarbons Facilitate Honey Bee (Apis mellifera) Colony Merging

Colony merging is one of the very important operations in beekeeping. For a safe merger, nestmate recognition is a prerequisite, which is caused by nestmate odors produced by certain volatile chemicals. Some of these chemicals are now known; however, knowledge about the entire spectrum of these chemicals is still lacking. In this article, we have attempted at exploring such chemicals. We investigated the recognition behavior of bees of different ages. Volatile cuticular hydrocarbons (CHCs) in bee groups before and after merging were analyzed via gas chromatography-mass spectrometry (GC-MS). The results indicated that newly emerged bees, which possess the lowest nestmate recognition ability, with less than 5% of observing time showing the defense behavior, develop recognition behaviors rapidly, reaching peak levels of over 35% of observing time showing the behavior at 8 days old and maintaining them throughout their lives. Each bee group has a unique CHCs profile. Merging significantly altered the original CHC profiles of bee groups. Four CHCs were up-regulated in the merged bee group. Ethyl oleate, hexadecanoic acid ethyl ester, and octadecanoic acid ethyl ester were further confirmed to significantly promote bee group merging by reducing 50% of the nestmate recognition ability (p < 0.05). These results highlight the importance of nestmate recognition in the social lives of honey bees, establish the chemical basis for honey bee nestmate recognition, and have potential practical applications in honey bee colony merging.