Wild Life Wonders: The Secret Life of Bumble Bees

CAES entomologist Tracy Zarrillo has identified 386 known bee species in Connecticut, including 16 different bumble bee species. Image credit: Ingrid Feddersen.

It’s not an accident that the phrase, “busy as a bee” became popular. Bees have always had the reputation for being hard workers by pollinating plants, collecting pollen and nectar, and building colonies.

Bees are an essential part of our ecosystem. They help the growth and repopulation of trees and flowers through their pollination, which then supports other insects. In turn, those insects support birds, bats, mammals, and everything up the food chain with food and shelter.

While some pollinating insects have a tough time getting at the pollen on plants like tomatoes, blueberries, and cranberries because the pollen is on the inside of the plant’s anthers, bumble bees are special and have no problem getting at their precious prize. In fact, bumble bees use a unique strategy called “buzz” pollination. “What the bumble bee does is land on the flower and vibrate its wings, using the same muscles for flying, but they don’t fly,” explained Tracy Zarrillo, an entomologist with the Connecticut Agricultural Experiment Station (CAES) in New Haven, Connecticut. The bumble bee stays on the flower and vibrates its wings at such a frequency that the pollen falls from the plant’s anthers and lands on the bee’s body. Then the bumble bee grooms itself, mixes the pollen with nectar which now has become a sticky substance, attaches it to a structure on their legs called a “pollen basket,” and carries it back to the colony for food for the larvae.

The lifecycle of a bumble bee is interesting, as well. Queen bumble bees, who have been mated by males in the fall, emerge in early-to-late spring from their underground hibernation and function as solitary bees. They are looking for a suitable nesting site. “This is an area where researchers are trying to find out where they’re nesting and why they’re nesting there, so that we can create more habitat for them,” Zarrillo said.

Left: Tracy Zarrillo, an entomologist with the Connecticut Agricultural Experiment Station (CAES) in New Haven, CT. Image credit: Bill Hobbs

Once the queen finds an appropriate site—it might be in an abandoned rodent hole, under a compost heap, or hidden in long, tangled grass—she then makes little wax pots and fills them with nectar from the flowers she visited. She will drink this nectar when the weather is too bad to forage. She also makes waxy brood cells and fills them with pollen and nectar and lays her eggs on top of these food stores. “She alone must forage for sustenance and take care of all nest duties. This is a crucial period in colony success, and springtime forage availability is a limiting factor, as well as exposure to pesticides,” Zarrillo writes in the “Connecticut Bumble Bee Guide,” an informative, online document (ctbombusguidepdf.pdf).

Four to five weeks later, the queen’s first brood hatches. They are all females, or “workers,” who eventually do the heavy lifting. As the colony grows and the queen’s daughters mature, they then take over all the domestic duties, fetching pollen and nectar, feeding the larvae, nest guarding, and nest cleaning, while the queen, called a “foundress” queen, stays put in the nest and devotes the rest of her life to laying eggs.

Finally, in late summer and early fall, when their colony matures, the foundress queen begins to produce males and new queens, called “gynes.” Zarrillo said these new queens then go off and mate with males from other colonies. And as the weather gets colder, the new impregnated queens will find a place to hibernate, completing the lifecycle, while the old queens, their daughters, and males die.

“The colony is only active for a year, unlike the honey bee which is perennial,” Zarrillo said. Bumble bee workers have a short lifespan of about four to six weeks, she said, but the queen is continually producing new workers. Bumble bee colonies can grow to have a mere 50 to 500 workers, depending on the species of bumble bee. This is unlike the honey bee, which can grow to have 50,000 to 80,000 bees in a colony.

Zarrillo grew up in Bridgeport, Connecticut, a self-proclaimed “city girl,” not having much affection for insects. Yet, later in life, she made a complete turnaround, earning an undergraduate and master’s degree from Southern Connecticut State University, studying, among other things, botany, ornithology, mycology, and entomology.

As a research assistant at CAES, Zarrillo was deeply influenced by Dr. Kim Stoner, a former vegetable entomologist and researcher on bees, and Dr. Chris Maier, an agricultural entomologist (both now retired), for whom she worked. Zarrillo took the job in 1992, expecting it to be an interim position, “but I ended up liking my job and loved who I was working for, and never left.”

Zarrillo is currently working on an inventory of all bee species that have been found in Connecticut. To date, 386 known bee species have been identified, including sixteen different bumble bee species. She hopes to have this list published by the end of the year. “A lot of people think that there are only bumble bees and honey bees. But what I’m trying to do is show people that there are many other kinds of bees that are pollinating, that are contributing to the crops and contributing to the eco-system,” she said.

Right: Late-season flowering plants that support bumble bees include New England aster, New York aster, white wood aster, Joe-Pye weed, blazing star, and goldenrod. Image credit: Niall Doherty .

If people are interested in attracting bumble bees, Zarrillo suggests planting the following “early season” plants for queen bumble bees: rhododendron, willows, blueberry, penstemon, crab apple, wild lupine, American holly, redbud, and dogwood. Examples of “late season” plants for bumble bee workers and gynes are New England aster, New York aster, white wood aster, Joe-Pye weed, blazing star, and the poor, misunderstood goldenrods. In fact, one of the best fall plants with the most bang for your buck to help support bumble bees and many other types of wild bees is the showy, yellow flowers of goldenrods. According to Zarrillo, goldenrods are primarily insect pollinated, unlike their allergy-causing cousin ragweed which is wind pollinated. Goldenrod pollen does not get airborne like ragweed pollen, hence it is not the likely culprit which makes one sneeze or causes itchy eyes in the fall.

So next time you see a bumble bee, you will be able to recognize that under that little buzzing sound, there’s an insect that has a major impact on our food, gardens, parks, and other natural areas.

Bill Hobbs is a contributing writer for Estuary magazine and The Times newspapers in New London, CT. He can be reached for comments at whobbs246@gmail.com.