The weakest bees foster survival of the colony.
Western honeybee colonies across North America are vanishing. No one has been able to pinpoint the exact cause of the mysterious Colony Collapse Disorder, but one likely culprit is Varroa destructor — a parasitic mite that invades honeybee colonies to reproduce, feed on the blood of bees, and spread disease.
Until recently, these mites were infesting colonies of Eastern honeybees in Asia, which would die off within a couple of years. Now, the original hosts are able to resist and even survive the onslaught, which is why the mites have switched to targeting the more common Western honeybee colonies.
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A research team has now figured out how the Eastern honeybees manage to survive mite infestations that are fatal to Western honeybees. Writing in the journal Scientific Reports, the researchers found that a greater number of infested Eastern bumblebee larvae succumb to their mites than do their Western counterparts. Weak and dead larvae, together with their parasites, are expelled from the colony by their siblings, preventing the mites from spreading.
The behavior is termed “altruistic suicide.” Study co-author Zheguang Lin from Zhejiang University said in a press release, "The behavior is comparable to that of honey bee workers that lose their lives when they defend their colonies. Their sting apparatus detaches from their body to remain in the intruder, which results in a fatal haemorrhage."
The findings elucidate how social insects cooperate in the face of parasitism. It is not necessarily strongest individuals that foster the survival of a honeybee colony, but counter-intuitively, it might be the weaker, more susceptible individuals, that do.
The results could also help beekeepers find ways to bolster Western honeybee survival in the presence of parasitic mites. "Considering individual susceptibility in breeding programs will improve colony health and contribute to a more sustainable global apiculture," said co-author Peter Neumann from the Institute of Bee Health.
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