Yellowjackets such as Vespula squamosa are nuisance predators of honey bees (Apis mellifera), preying on them and pillaging their honey. But bees fight back, and healthy bee hives are rarely at risk, according to experts. (Photo credit: Flickr/Insects Unlocked/Alejandro Santillana)

By Edward Ricciuti

The boom in backyard beekeeping in recent years has been great news for at least one group of fellow hymenopterans: yellowjackets. Honey bees are high on the menu of insects on which yellowjackets feed; besides killing and eating individual bees, yellowjackets also raid hives for larvae, pollen, and honey. More beekeepers means more bees to consume and hives to pillage.

Ed Ricciuti

To be sure, yellowjackets—a term used in North America for two genera of social wasps, Vespula and Dolichovespula—are not a leading (or even significant) cause of honey bee colony losses. But when yellowjackets do target honey bees, they hang around the entrance of a hive waiting to ambush and pick off individual bees as they come and go. They quickly dismember a bee after killing it, eating some parts and carrying a portion back to feed their own larvae in their own nest. Beyond that, says Mark Creighton, master beekeeper and apiary inspector for the State of Connecticut, healthy hives are seldom seriously threatened by yellowjackets.

A similar opinion is voiced by author of the highly regarded book The Sting of the Wild, Justin O. Schmidt, Ph.D., of the Southwestern Biological Institute in Tucson, Arizona: “In North America,” he says, “yellowjacket predation on honey bees is not a major problem in most cases.”

That’s because honey bee (Apis mellifera) hives have a formidable defense. Worker bees assigned as guards fight off intruders with stings, and they will also cluster in a ball around individual yellowjackets and “cook” them to death with body heat, which has been recorded at more than 120 degrees Fahrenheit. A dozen or so bees can do the trick on one yellowjacket.

If a hive weakens, on the other hand, all bets are off. Attacks by yellowjackets can go from a nuisance to a genuine problem and even lead to hive collapse, says Creighton. Yellowjackets easily sniff out chemicals that reveal weakness in a hive, upon which they trigger an all-out assault by chemically signaling for reinforcements. They then proceed in looting honey cells and killing bees, often including the queen.

Many forces can weaken a hive, including chemical pollution, pesticides, and poor management. The increasing numbers of novice beekeepers, says Creighton, increase the likelihood of management mistakes, improving opportunities for rapacious yellowjackets.

To avoid mistakes, says Creighton, novice beekeepers should take an introductory course and learn from a mentor. He explains that beekeeping in North America has become more demanding since the 1990s, due to the tiny brown Varroa mite, which has spread almost worldwide from Asia. Its scientific name, Varroa destructor, is frighteningly appropriate because it feeds on bees and spreads viral disease that kills hives—worldwide, it is generally regarded as the worst of all bee parasites.

“The Varroa mite changed everything,” says Creighton.

A hive has a full menu for a hungry yellowjacket: adult bees and larvae for protein plus honey and pollen for carbohydrates. Hives and the bees living in them are particularly important later in the season because other prey insects and nectar sources are dwindling. “In mid-to-late fall when food is scarce and some honey bee colonies are weak, yellowjacketes might invade and do some serious damage.” says Schmidt.

Vespula squamosa, sometimes known as the southern yellowjacket. (Photo credit: Flickr/Insects Unlocked/Alejandro Santillana)

Vespula squamosa, sometimes known as the southern yellowjacket. (Photo credit: Flickr/Insects Unlocked/Alejandro Santillana)

Even if experts downplay damage caused by yellowjackets, the predators take plenty of flak for wrecking hives. Beekeeping organizations and state agricultural agencies churn out a flood of information on how to fight off the yellowjacket hordes. Countermeasures range from simply narrowing the entrance to the hive to prevent easy access by predators to a host of eradication tactics.

This concern seems to be a tad of overkill. “Overall,” says Schmidt, “yellowjackets are beneficial insects, and their benefit outweighs their harm to bee colonies.” Indeed, yellowjackets prey on a variety of grasshoppers, aphids, flies, and caterpillar pests. They may be at times a beekeeper’s bane but overall can be a boon for agriculture.

Part of the reason why yellowjackets have taken such a bad rap in this country, says Schmidt, is because of confusion involving yellowjackets and hornets, much of which is caused by local and common names given these insects. Yellowjackets and hornets are both wasps in the family Vespidae. But they are by no means the same. “Yellowjacket” is a name given in North America to two groups of wasps, the genera Vespula and Dolichovespula. The latter in North America is represented by what most people call the “bald-faced” or “white-faced” hornet, although it really is not a hornet but rather a yellowjacket.

Dolichovespula maculata is known as the baldfaced hornet even though it belongs to one of the two genera—Vespula and Dolichovespula—collectively termed yellowjackets. (Photo credit: David Cappaert, Bugwood.org)

Eastern yellowjacket (Vespula maculifrons). (Photo credit: Johnny N. Dell, Bugwood.org)

Hornets (genus Vespa), meanwhile, are not native to North America, although the European hornet (Vespa crabro) has been introduced there. In Europe and Asia, however, hornets are a serious problem to beekeepers. The notorious giant Asian giant hornet (Vespa mandarinia), a beast two-and-a-half inches long, is a true plague of honeybee hives. It is spreading and could be a nightmare for beekeepers if introduced here.

Speaking of introductions: One of the most abundant, widespread, and aggressive of the wasps that North Americans call yellowjackets is, in fact, not native to North America but rather introduced from the Old World. In North America, it’s called it the “German yellowjacket” (Vespula germanica). In Europe, however, it is just a “wasp.” There is a good reason for scientific names.

Ed Ricciuti is a journalist, author, and naturalist who has been writing for more than a half century. His latest book is called Bears in the Backyard: Big Animals, Sprawling Suburbs, and the New Urban Jungle (Countryman Press, June 2014). His assignments have taken him around the world. He specializes in nature, science, conservation issues, and law enforcement. A former curator at the New York Zoological Society, and now at the Wildlife Conservation Society, he may be the only man ever bitten by a coatimundi on Manhattan’s 57th Street.