Winter bumble bees and wildflowers
[wpvideo wjlv1q8k] This video and photos in this blog post show numerous bumble bee species foraging on non-native heather (Erica spp.) plants in our garden on February 24, 2016.Early emerging bumble bees are hard pressed to find flowers in February, but there are some native plants flowering already that they can utilize. I have seen snow queen or spring queen (Synthyris reniformis) and Nuttall’s toothwort or spring beauty (Cardamine nuttallii) blooming in the canyon I live in, along with several different species of willow (Salix spp.). The first Indian warrior (Pedicularis densiflora), gold stars (Crocidium multicaule) and native violets (Viola spp.) are all blooming in the Klamath-Siskiyou at low elevations, and the grass widows (Olsynium douglasii) will be blooming soon on sunny slopes and rock outcrops. For the bumble bees, spring will soon begin in earnest.
It’s still winter in the Klamath-Siskiyou, but the warm, spring-like days this February have brought out the bumble bees! Bumble bees are some of the first bees seen in the spring because they are specially adapted to be active in colder weather than most other bees.
The Bees In Your Backyard: A Guide to North America’s Bees gives the following information about bumble bees:
- The name Bombus comes from the Greek word bombos, which means “a buzzing sound,” referring to the low hum these bees make as they fly gracefully around flowers. The common name “bumble bee” can be traced back to the word bombelen in Middle English (AD 1200-1500), which means “to hum.” In fact, prior to the 1920s, bumble bees were more often called “humble bees,” also a reference to the soft droning inherent in their foraging activities. The term “humble bees” was used by both William Shakespeare in A Midsummer Nights Dream and by Charles Darwin in On the Origin of Species. A few popular articles in the 1920s about Bombus referred to them as “bumble bees” and the new name took.
- Bumble bees are among the few bees native to North America that are truly social, with a queen and workers.
- Like European honey bees, bumble bee workers collect copious amounts of nectar, which they bring back to the hive for storage. Unlike honey bees, however, the bumble bee workers do not dehydrate the stored nectar, turning it into honey. Instead this nectar is used by bumble bees, along with pollen, to feed the developing young. Because bumble bee hives begin anew each year, there is no need to store large amounts of nectar as honey to sustain the workers through the winter the way that honey bee colonies must.
- Studies have shown that for many crops, pollination by bumble bees produces bigger fruit, faster fruit set and larger yields than other pollination methods, most specifically honey bee pollination. First, bumble bees have a distinct advantage over European honey bees when it comes to retrieving pollen from some plants: they can buzz pollinate. They are therefore much more effective pollinators of some important crops, specifically with flowers requiring buzz pollination. These plants include tomatoes, peppers, eggplants, potatoes, and even some berries like blueberries. Second, bumble bees have been shown to be faster workers than honey bees, often visiting twice as many flowers per minute. Finally, researchers have estimated that bumble bees will do at least eight times more work than a honey bee because bumble bees can remain active in cold temperatures, and they can carry more pollen.
- Bumble bees have special adaptations that allow them to be active in colder weather and colder climates than most other bees. In addition to their thick and insulating coat of hair, bumble bees often bask in the sun to warm themselves before they head out to forage. When sun and fuzz aren’t enough, bumble bees can actually generate heat internally by shivering their flight muscles. These bees can uncouple their wings from their flight muscle, allowing them to contract the muscles without flapping their wings. Those muscle contractions can raise the internal temperature of the bee, making them significantly warmer than their surrounding environment. In fact, bumble bees can’t take off and fly until their flight muscles are above 80 degrees; by shivering their flight muscles to warm up, they can actively forage in temperatures much too cold for other bees.
- Unlike honey bee queens, a bumble bee queen lives for only a single year. This annual cycle generally keeps bumble bee hives much smaller than the hives of honey bees. Most mature bumble bee colonies consist of fewer than 200 bees, although some can have as many as 1000 individuals. For comparison, European honey bees may have around 60,000 bees in a single colony.
- Most bumble bee species make their nests in the ground, often in preexisting cavities like abandoned rodent burrows, in piles of wood, or in leaf litter.