Meet the Pollinators: Bumblebees and Their Queen
By Jill Eisenstein, Master Gardener Volunteer
Enter the queen. After a long winter of hibernation, usually underground and sometimes in old mouse nests, the mated and hungry queen bumblebee emerges with a solitary mission: start a new hive. She is a perfect match for Dutchman’s breeches, which look just like white pantaloons hanging upside down to dry. She can pry open the inner hinged petals and is the only early pollinator with a tongue long enough to reach the nectar deep inside the spurs, pollinating the flower in the process. This flower and bumblebee queen fit together like puzzle pieces in a grand design.
Any bumblebee observed in early spring is undoubtedly a queen bumblebee. She is strong enough to fly in cool weather and low light conditions. Besides spring ephemerals, she visits apple, serviceberry, other tree blossoms, and pussywillows. She works alone, gathering nectar and pollen, laying eggs, then rearing a brood of all female workers to take over the daily job of foraging. The pollen she ingests in very early spring eventually stimulates pheromones in her body that signal her to find a nest site.
There are nearly 50 species of native bumblebees (Bombus spp.) in North America. The bees are mostly black and yellow, round, and hairy with short wings. They are one of the few native bees that are “social” rather than “solitary”; their egg-laying queen raises an entire colony that is active for just one season. Interestingly, even with a colony to protect, female worker bees are usually docile, seeming too busy foraging to bother stinging.
The new generation of bumblebees emerges as the spring ephemerals die back and completely disappear from the forest floor, about four weeks from when the eggs were laid. Being smaller than the queen, worker bees are better suited to bright meadows and sunny gardens where a parade of blooms feeds them through the summer and fall. They are generalists, visiting many different flower species, but exhibit flower “constancy”, getting as much as possible from one species of flower before learning how to get food from the next.
Bumblebees pollinate crops from late spring through summer, including strawberries, blueberries, raspberries, cucumbers, peppers…and bumblebees, unlike honeybees, can pollinate all members of the nightshade family, including tomatoes. They have perfected a special pollination technique called “buzz pollination” where they grasp the anther of the flower and vibrate their wing muscles to literally shake the pollen from the flower. Though tomatoes don’t strictly need pollinators for survival, studies have found that buzz pollination increases fruit size and yield.
Bumblebees have small nests, between the size of a baseball and a softball. The queen lays a few broods since the average worker’s adult life only lasts about four weeks. She lays another brood of bees late in the season which, unfertilized, are all males. Once the males emerge, she will lay more female eggs for new queens, a process regulated by pheromones so that they will be bigger. Once the new queen bees emerge, fatten up on nectar, and mate, they begin immediately to look for hibernation sites. The entire bumblebee colony from that year dies off in late fall, leaving just the new mated queens to start new colonies in the spring. If even one of these queens dies, a whole colony remains unborn.
Many bumblebees are listed as endangered, vulnerable, or threatened. A few years ago, the rusty patched bumblebee (Bombus affinis) was the first bee listed as an endangered species in the continental U.S. According to the USDA, the decline in bumblebee populations can be blamed on the 5 “P’s”— poor nutrition, pesticides, parasites, pests, and pathogens. Want to help them?
Give them healthy food. Bumblebees get all their food from flowers. To provide the best nutrition, consider native plants, including early blooming native trees and shrubs. Plant flowers that will bloom successively spring through fall, including the beauties of latest fall, asters. Most species of bumblebee show a preference for violet or blue flowers but will forage from others. For ideas, see our bloom chart. The link to the chart is also on the left side of the Putnam Pollinator Pathway Page.
Eliminate pesticides. Ask your local nursery to make sure that no systemic or other pesticides were used on the plants you are purchasing. This includes granular applications in nursery pots, or in sprays applied to bedding plants. Instead of pesticides in your landscape or garden, try companion planting, attracting natural predators of your pests, or using low-residual pesticides like horticultural soaps or oils. helpful publication.
To provide hibernation and nesting sites, leave some part of your yard a little wild and brushy. Don’t mow or rake there to give the new queens places to hibernate and spots to establish new colonies in the spring. details of leaving hibernation sites.
It is often thought that hummingbirds have the highest metabolic rate of all animals, however the metabolic rate of bumblebees is 75% higher than a hummingbird's!