Italian Honey Bees Caught Robbing Pollen from Bumblebees

Some honeybees in Italy have been caught red-handed stealing pollen from unsuspecting bumblebees. Honeybees rely on pollen as a vital source of protein, and it seems that some are willing to go to great lengths to obtain it, even resorting to theft from other bees.

This phenomenon of pollen stealing has been observed previously in the United States, but now researchers in Italy have documented honeybees snatching pollen directly from the backs of bumblebees. These observations, published in Apidologie on December 21, provide one of the most comprehensive accounts of bee-on-bee larceny to date.

During a summer expedition in 2019 to Mount Antola in the northern Italian region of Liguria, independent naturalists Tiziano Londei and Giuliana Marzi, both based in Milan, captured video footage of honeybees (Apis mellifera) seemingly trying to displace bumblebees from a woolly thistle flower (Cirsium eriophorum). However, upon closer examination, it became evident that this was not mere competitive behavior but a full-fledged robbery.

As the red-tailed bumblebees (Bombus lapidarius) scoured the flowers for nectar and pollen, some of the pollen grains adhered to their hairy bodies. Londei and Marzi observed honeybees shamelessly pilfering this pollen for their own use. Interestingly, the thieves displayed a slight preference for male bumblebees, as they seemed less bothered by the theft, although even the females did not respond aggressively.

According to Avery Russell, a biologist at Missouri State University who was not involved in the study, honeybees are notorious for their pollen-hoarding tendencies. Therefore, stealing pollen from bumblebees does not come as a surprise to him.

To assess the prevalence of this criminal behavior, the researchers revisited the site twice over the following three years and also observed bees at two other locations approximately 25 kilometers away. While honeybees at these other sites were not observed stealing from bumblebees, those at the initial site continued their larcenous activities year after year. For example, honey bees collect pollen from only three out of 31 flowers observed in 2021 but stole from 28 out of 66 available bumblebees.

Upon scrutinizing the differences between these sites, the researchers speculate that honeybees resort to theft in areas where collecting pollen from flowers is challenging (such as the woolly thistle) but where there is an abundance of other bees present.

Previously, pollen stealing by honeybees had only been reported in North America, first in Kansas and later in California and Indiana. The discovery of this behavior in Italy suggests that it may be a widespread phenomenon. Russell expresses the need to investigate whether pollen theft has any negative impacts on bumblebees or the flowers they pollinate. Furthermore, he wonders if other bee species also engage in pollen theft, stating that bumblebees in hives have been observed nibbling on each other's pollen baskets.

Source: sciencenews.org