You may think of honey bees as yellow and black-striped harbingers of spring, destined to flit between flowers and produce sweet honey. Their impact is far greater than the honey they produce, however; honey bees directly or indirectly produce one out of every three foods. It is therefore very concerning that bee populations have been declining—entire hives have been dying without any obvious explanation. One potential culprit is the Varroa destructor mite, a small pest believed to feed on the blood of honey bees. Recent research from the University of Maryland that suggests the mites don’t feed on the bees’ blood, but their fat. These insights can guide further research in protecting honey bee colonies from the mites.

The researchers exposed honey bees to the mites and observed the mites’ actions. The mites mostly attached to the fatty backs of adult bees, but they also attached themselves to any part of the fatty immature bee pupae. To further test the hypothesis that the mites were feeding on fat, the scientists fed the bees two types of dye. Green uranine made its way into the bees’ blood, but bright red Nile Red dye found a home in the bees’ fat. After releasing the mites to feed on the bees, the biologists looked at the mites under a microscope. The mites were bright red, indicating that they had been feeding on the bees fat. As a final test, the researchers split the parasitic mites into several groups, separated from the bees. One group was fed only bee blood, another was fed only bee fat, and the other groups were fed different amounts of both blood and fat. At the end of the week, all of the mites fed any amount of blood had died, only the mites fed pure fat survived. The fat-fed mites were also the most likely to have laid eggs over the course of the experiments.

Knowing that the Varroa destructor mites feed on bee fat is an important insight for beekeepers and scientists concerned about declining bee populations. Bees need their fat to build their immune systems, protect them from pesticides, survive the winter, and create waxy bodies that protect them dehydration. Understanding how the mites act on bees can guide researchers in developing strategies to protect bee colonies from the parasitic mites.

Managing Correspondent: Emily Kerr

Press Article This honeybee parasite may be more of a fat stealer than a bloodsucker

Original Journal Article: Varroa destructor feeds primarily on honey bee fat body tissue and not hemolymph

More About Bees: Bee Benefits to Agriculture