'Aggression, Fighting And Pheromones': Rare 'Cuckoo' Bumblebee Spotted In Survey

Jul 18, 2018

Researchers are surveying bumblebees at four northeast National Wildlife Refuges in New Jersey, Pennsylvania, Maine and Vermont this summer. During the Vermont survey in the Missisquoi National Wildlife Refuge in Swanton, surveyors say they made an unusual find: a bumblebee that's only been seen twice before in Vermont.

The surveys aim to establish baseline data amid an ongoing worldwide decline in bumblebee numbers. Roughly a third of Vermont's nearly 50 native species are experiencing what's considered "significant decline."

The fall has been attributed to habitat loss, pesticide use, and parasites, among other factors. Fewwer bees threatens ecosystems, biodiversity, and even Vermont’s food system, as bumblebees are important pollinators of both wild plants and crops.

Leif Richardson, a senior ecologist with environmental consultants Stone Environmental and part of the Vermont's bumblebee survey in the Missisquoi refuge in Swanton, said his work in the reduge gave him a glimpse of an especially elusive bee: Fernald’s bumblebee, Bombus fernaldae.

"There are two historic records for this bee in Vermont," Richardson said. "There’s a specimen that was taken in 1936 in Whittingham [and] a second that was taken in Island Pond in 1963. Just two dots on the map."

Fernald's bumblebee is fairly common elsewhere in the region—it's been spotted in Quebec, New York, and Maine—but confirming the bee is still found in Vermont is an important data point, Richardson said. Since his survey, he says fourth and fifth sigthing of the bee have been recorded in the state.

The bumblebee is interesting for another reason, Richardson said, and it has to do with how it builds its colony and marshals its worker bees. Or, more specificially, how it doesn't.

"Fernald's bumblebee is a cuckoo bumblebee. These guys are not social, they don't found a colony where there's a social structure. Instead, it just sneaks in and takes over the workforce of another species of bumblebee." - Leif Richardson

Richardson said cukcoo bumblebees, including Fernald's, "use a combination of aggression, fighting, and pheromones to either kill or subjugate the resident queen. They’ll eat the eggs and the larvae and any pupae there, and they’ll lay their own eggs. And then, using pheromones, they’ll induce the resident worker population to rear those offspring."

Such social parasitism isn't uncommmon among bumblebees, Richardson notes. The host colony ultimately dies as the young bees of the social parasite go on to mate, hibernate, and awaken the next spring to repeat the cycle all over again. Richardson describes it as all part of nature's rhythms.

"It's this fascinating part of natural history, and I'm glad to know that this species persists in Vermont."

Amature melittologists can assist Richardson and other bee researchers in their work by snapping photos of bumblebees and sharing them with online through sites like Bumblebee Watch or iNaturalist.

You never know when you might spot your own glimpse of the elusive Fernald's bumblebee.

Broadcast on Wednesday, July 18, 2018 at noon; rebroadcast at 7 p.m.