One of my favorite bumblebees is the golden northern bumblebee, but I hadn’t seen one since 2020. Imagine my surprise and delight when I encountered one in my Somerville community garden recently! This bumblebee is fuzzy and nearly completely yellow. It is also uncommon and probably in decline.
The one I saw was a male. This is a sign the season is ending, because that’s when bee colonies produce males and new queens. The males have only one job – to hang out on flowers until they can mate with a newly hatched queen, after which the new queen stores the sperm, finds a suitable place to overwinter and reemerges in the spring to start a new colony. All the other bees die.
So much depends on the new queen. If she does not survive the winter or is unable to find enough food in the spring – she faces many hazards – the entire colony’s genes will die out.
Some bumblebees have become extinct where they were once abundant. New research has documented that there are 50 percent fewer bumblebees in North America than in 1974.
Bumblebees, and bees in general, are found mostly in temperate climate zones and do not enjoy extreme heat: Baby bumblebees grow best when nest temperatures are between 82 and 90 degrees Fahrenheit. When nests reach 95 degrees, the baby bees die.
Research by scientists examining 66 bumblebee species on two continents seems to confirm that extreme heat reduces colony size and increases extinction rates – and according to the National Oceanic and Atmospheric Administration, this past July was the warmest July on record in North America. New Hampshire and California were the most above average, but Massachusetts was not far behind. Last year, 2023, was the warmest year since people began keeping records.
Beside extreme heat, pesticides kill bumblebees, who nest in the ground. In addition, nonnative bees that people raise (such as honeybees) also push out bumblebees. With all these stressors, it is not surprising bumblebee populations are declining.
With a little luck, the queen survives the winter and emerges in the spring. She builds up her strength by feeding on nectar and pollen. Then she builds a small nesting chamber in tall grass or in cavities just below the ground. She produces waxy flakes that she forms into a cup, which she fills with nectar. Nearby, she packs pollen into a clump. On the clump, she lays eggs. She sits on the eggs, shivering her flight muscles to generate heat to keep the eggs warm. If the weather is too cold to leave the eggs to visit flowers, she drinks nectar from the nectar cup.
After about five days, the eggs hatch into wriggling larvae. They eat the pollen around them. The queens has a difficult task: She not only must keep the larvae warm, but also must leave to collect nectar and pollen to feed herself and her offspring. If she is unsuccessful at either, the little colony dies.
After a couple of weeks, the larvae spin cocoons, inside of which they transform into adult female worker bees. When the new adult bees emerge, they collect nectar and pollen so the queen can retire from collection duties and focus instead on laying more eggs to increase the size of the colony. The worker bees are now solely responsible for feeding the larvae and caring for the nest. In this way the colony grows over the summer.
Golden northern bumblebees work so fast and so hard that they do not live long, even compared with other bumblebees. Worker bees need lots of pollen to feed the larvae, so they visit many flowers, pollinating them in the process. They are essential pollinators of native flowering plants with which they have coevolved. Golden northern bumblebees are the fastest workers I have ever seen – hyperactive speed demons who can collect pollen from 44 flowers per minute! It is not surprising then that these worker bees do not live long, and, in fact, some die from exhaustion.
In late summer, the queen lays eggs that hatch into males and new queens. (Males arise from unfertilized eggs; queens are simply workers who are fed three times more than other larvae.) The bigger the queens, the better their chances of surviving a harsh winter. If all goes well, a queen will live for about a year.
Golden northern bumblebees are active in the afternoons – the hottest part of the day. Their long tongue allows them to reach into long, deep flowers, which many other bees cannot reach. They favor thistles, monarda (bee balm), zinnias, red clover, beardtongues (penstemon), honeysuckles and vetches.
There are some things you can do to help golden northern bumblebees (and all bumblebees). Some of the most important are to plant native flowers and avoid using pesticides. Green spaces, especially in hot urban areas, can help shade and shelter bees from extreme heat. Newly emerging queen bees need spring-blooming flowers and trees, for without these flowers they will not survive long enough to start a colony. Bumblebee colonies store enough food for only a few days, so bees die if there are not enough flowering plants throughout the entire season. Lastly, leave the leaves in your yard until spring. Many insects, not just bees, may be overwintering in or under the leaves.
Seen nearby
Jimmy James spotted this red-tailed hawk on Cambridge’s Rindge Avenue on Aug. 19.
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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.
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