Friday, June 14, 2024

A shaggy perplexing bumblebee in Somerville on July 17, 2021. (Photo: Jeanine Farley)

Ralph Waldo Emerson called bumblebees “yellow-breeched philosophers.” There are five common yellow-breeched philosophers in our area: the common eastern bumblebee, the two-spotted bumblebee, the brown-belted bumblebee, the golden northern bumblebee and the perplexing bumblebee (Bombus perplexus) – perhaps the least common and least well-known of these. These bees are mostly yellow and may be confused with the golden northern bumblebee, which is also mostly yellow. If you look closely, though, the perplexing bumblebee has long shaggy hairs and may have some black at the end of its abdomen.

Bumblebees have a very different life cycle from honeybees. A bumblebee colony exists for only one season: In the spring, a single queen comes out from hibernation and starts a colony by first building a nest.

A perplexing bumblebee alights in Devens on July 19. (Photo: Robert Gessing)

Perplexing bumblebees live in small colonies made up of one queen and dozens of female worker bees. (Honeybee colonies can contain 50,000 bees, but bumblebee colonies have only a few hundred workers at most.) They nest on the surface of the ground and in hollow logs and trees, so they are extremely susceptible to poisoning by lawn chemicals and pesticides.

A perplexing bumblebee forages on a flower in Somerville’s Ball Square on July 17, 2021. (Photo: Jeanine Farley)

After the queen selects a nesting site, she lays eggs to form a colony. She alone forages and cares for the eggs and larvae. This is a critical phase – if the queen cannot find food or is poisoned by pesticides, the nascent colony will perish. The first winged worker bees emerge from cocoons in late May or early June. Once the first workers emerge, the queen stops foraging and focuses solely on laying more eggs to enlarge the colony as the summer progresses. Around midsummer, the queen lays eggs that develop into male bees and new queen bees. Around September, the new queens mate with the new male bees. The males die, and the young queens hibernate until spring when the process starts anew.

Perplexing bumblebees are darker yellow than many other bumblebees. (Photo: Norm Levey)

The queen stores sperm in a special chamber in her body. She allows some of her eggs to become fertilized. The fertilized eggs grow into female worker bees and queen bees. Unfertilized eggs become male bees. The eggs hatch in four days, and the queen or worker bees feed the larvae pollen (protein) mixed with nectar (sugar) for two weeks. Then each larva spins a cocoon and develops for two more weeks into a full-sized adult bee. The first bees that hatch are all female worker bees. Later in the season, male bees and new queens are produced. The males feed on nectar only, which sustains them while they look for a mate.

Bumblebees are valuable pollinators, for unlike honeybees, they forage during cold, rainy and cloudy weather. They are essential pollinators of native flowering plants with which they have coevolved. Bumblebees visit hundreds of native plant species, whereas invasive honeybees, for example, are excellent pollinators of invasive plants such as Japanese knotweed. Native bees rarely visit Japanese knotweed.

Perplexing bumblebees do not have black hairs between the wings. (Photo: Robert Gessing)

Perplexing bumblebees have a medium-length tongue, so they have a preference for hydrangeas, rhododendrons, thistles, honeysuckles, sweet clover, foxglove beardtongue and blackberries.

Bumblebee colonies store only a few days’ worth of food, so the bees can die if there are not enough food sources available throughout the entire season. It is important, therefore, that we plant a variety of native flowering plants to support our native bumblebees all spring and summer long. Bumblebees are gentle, nonaggressive bees. They will not chase you; they sting only in self-defense.

A spring perplexing bumblebee searches for nectar and pollen in Medford on May 25, 2021. (Photo: Jeanine Farley)

These bumblebees, like many, are declining in numbers. Pesticides, habitat loss and being pushed out by nonnative honeybees are likely reasons.

Charles Darwin recognized the importance of bumblebees (which he called humble bees) back in 1859:

I have found that the visits of bees, if not indispensable, are at least highly beneficial to the fertilization of our clovers; but humble bees alone visit the common red clover (Trifolium pratense), as other bees cannot reach the nectar. Hence, I have very little doubt, that if the whole genus of humble-bees became extinct … red clover would become very rare, or wholly disappear.

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Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.

This post was updated April 26, 2023, to correct the spelling of Jeffrey Offermann’s name.