By Meredith Swett Walker
When the temperature drops and the days get shorter, honey bees don’t hibernate—they huddle. Meanwhile, worker bees produced in the fall are plump and have longer lifespans than their spring counterparts. These winterized workers form a “thermoregulatory cluster” around their queen. Powered by honey stores, they shiver their muscles to produce heat, keeping temperatures at the center of the cluster around a comfortable 21 degrees Celsius (C). Still, winter is a stressful time for honey bee (Apis mellifera) colonies. In the United States around 30 percent of colonies don’t survive until spring.
In Europe, overwinter survival of honey bee colonies is generally better, and evidence shows that honey bee populations may be “locally adapted” to regional climatic conditions. For instance, honey bees originating in Greece are less likely to survive a winter in Finland than are local honey bees. But honey bee populations in North America are a lot more “geographically scrambled.” That’s because commercial beekeepers in North America routinely move bees great distances. Colonies providing pollination services are moved around the U.S., and queens are shipped great distances by breeders. So, locally adaptive genetic traits may not necessarily stay in the place where they are advantageous.
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