Kevin MacDonald, Ph.D.

CSULB, Department of Psychology

How some bees deal with parasites

Bees jail offenders

TOM CLARKE
From Nature Science Update, May 22, 2001

On guard: bees sap inmates' life.

© SPL

South African honeybees adopt a strict incarceration policy to control a troublesome hive parasite currently terrorizing their European cousins.

Small hive beetles (Aethina tumida), native to South Africa, have begun to cause havoc in US hives of European honeybees (Apis mellifera spp.). Beetle larvae feed on developing bees and their stores of pollen and honey.

With aggression and "nice teamwork" South African Cape honeybees (Apis mellifera capensis) apprehend and imprison the intruders, says Peter Neumann of the Martin Luther University in Halle, Germany. Neumann and his colleagues watched the bees' hard-line tactics for 57 days.

"Small hive beetles are like tanks," says Neumann. The rounded beetles' tough armour makes them impervious to stings, a bee's normal response to harmful parasites and predators.

So worker bees hustle the beetles into cracks and corners, and take turns guarding them. They then seal the parasites in with fast-setting tree sap. The beetles starve to death.

If there are too many parasites to imprison permanently, guard bees hold the beetles long enough for their fellow bees to abscond and set up a hive elsewhere. "It gives them time to tell the queen: 'ok, we have to get out of here'," Neumann says.

European honeybees also collect and use tree sap as a sealant and can rout other parasites, but they allow small hive beetles to run riot. Neumann suspects that, having evolved in isolation from the parasite, they have simply not learned to corral the beetles and imprison them. "European colonies can cope with other parasites, so it's not as if they're lazy," he says.

Since arriving in the United States in around 1996, small hive beetles have spread across the Southeastern states. Last year they cost Florida beekeepers alone $3 million, according to Patti Elzen, an entomologist with the US Department of Agriculture in Weslaco, Texas. The beetles will probably overrun other warm parts of the United States, says Elzen.

Currently, insecticides are used to control small hive beetles in American beehives. Neumann's work may be a promising lead in the search for better alternatives, says Elzen. Breeding docile, honey-producing European honeybee strains that get tough on beetles could be an ideal natural control method.

But jailbird beetles may not be completely at the mercy of aggressive bees. Neumann's team observed four jailbreaks (all at night), two cases of beetles mating while incarcerated and one beetle eating its cell mate's body in the face of starvation. "Although there's no clear-cut evidence, these may represent survival tactics," says Neumann.

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Neumann, P. et al. Social encapsulation of beetle parasites by Cape honeybee colonies. Naturwissenschaften (In the press, 2001).