How ‘Undertaker’ Bees Recognize Dead Comrades
Arthur T Knackerbracket has found the following story:
Wen Ping, an ecologist at the Chinese Academy of Sciences's Xishuangbanna Tropical Botanical Garden, wondered whether a specific type of scent molecule might help undertaker bees find their fallen hive mates. Ants, bees, and other insects are covered in compounds called cuticular hydrocarbons (CHCs), which compose part of the waxy coating on their cuticles (the shiny parts of their exoskeletons) and help prevent them from drying out. While the insects are alive, these molecules are continually released into the air and are used to recognize fellow hive members.
Wen speculated that less of the pheromones were being released into the air after a bee died and its body temperature decreased. When he used chemical methods of detecting gases to test this hypothesis, he confirmed that cooled dead bees were indeed emitting fewer volatile CHCs than living bees.
Wen then designed a series of experiments to see whether undertaker bees were picking up on this change. He turned to five hives belonging to Asian honey bees (Apis cerana Fabricius), a small, hardy insect found across Asia, and began to heat up the corpses of perished honey bees. When he placed regular, cool dead bees in a hive, workers always removed them within half an hour. However, when he placed the bee in a heated petri dish and warmed it up by a few degrees Celsius, it often took undertakers several hours to even notice the body. That's presumably because the warm bee body was releasing close to the same amount of CHCs as a living bee, he reports in a preprint published this month on bioRxiv.
To seal the deal, Wen washed the CHCs off dead bees with hexane, which can dissolve waxes and oils, heated them up to about the temperature of a live bee, and placed them back in their respective hives. The undertakers sprang into action and removed nearly 90% of the hot, clean dead bees within half an hour. That suggests it's not temperature, but the absence of CHC emissions that undertakers use to diagnose death.
Journal Reference:
Ping Wen. Death recognition by undertaker bees, bioRxiv (DOI: 10.1101/2020.03.05.978262)
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