By Sam Burbach, Education & Programming Coordinator – 06/23/2020
Bees are the most important group of pollinators, as they do the largest amount of pollinating. Bees pollinate about 80 percent of flowering plants, and here in the United State, bees pollinate approximately 75 percent of the fruits, nuts, and vegetables that we grow.
What makes bees such great pollinators? While most other pollinators unintentionally pollinate flowers, bees deliberately seek out pollen to use as a food source for their offspring which makes them very effective pollinators. Bees have special adaptations on their hind legs or under their abdomen to transport pollen – pollen baskets for honey and bumble bees, and scopa for other species of bees. While visiting up to hundreds of flowers in a single foraging trip to collect pollen and nectar, the bee inevitably transfers some of the pollen from flower to flower, thus initiating the pollination. Some bees even utilize a specialized technique known as “buzz pollination” to loosen tightly-held pollen from some flowers – more about this technique later.
When thinking about bees, most people first think of honey bees and/or bumble bees, but there are so many more bee species than that. There are an estimated 20,000 species of bees worldwide, and there are over 4,000 species of native bees in North America. Another fact many people might not realize, is that honey bees are not native to North America. Let’s explore some different groups of bees!
More than 90 percent of bee species in North America live a solitary life, rather than social lives like we see with honey bees. Some solitary bees will build nests in groups or “aggregations,” but each female solitary bee builds her own nest and lays eggs. About 70 percent of solitary bees nest in the ground, while the other 30 percent nest in hollow stems or twigs, chew holes into dying wood, or even use abandoned beetle burrows. Most solitary bees are not aggressive, and many are stingless.
Solitary bees have scopa, or a dense mass of hairs on their hind legs and under their abdomens, to transport pollen from the flowers back to their nest. These long, branched hairs are effective at holding pollen but they inevitably drop pollen along the way, which makes solitary bees very efficient pollinators.
Pictured below are two species of Nomad bees.
Bumble bees are the only native North American bees that are truly social, meaning they live in colonies, have a caste system, and have overlapping generations; however, a bumble bee colony has an annual life cycle, meaning that only the newly hatched, fertilized queens will survive to hibernate into the following spring. Upon emerging from hibernation, the queen will find a nesting cavity (usually underground), creates some brood cells, adds pollen and nectar for food, and then lays eggs. After about four to five weeks, these female bees will emerge as adults and become worker bees who will help forage and tend to the nest while the queen continues to lay eggs. Near the end of summer, male drones and new queens will emerge and mate, then the queens will hibernate to start the cycle over.
Bumble bees are often the first pollinators in late winter and the last pollinators in fall so they forage on a wide variety of flower species. Bumble bees can also use a technique known as “buzz pollination” to access pollen that is stored tightly to or even inside the anther of some flowers, such as blueberries and tomatoes. In buzz pollination, the bee will grab the anther in her jaws, unhinge her flight muscles, and vibrate them at a rapid pace to dislodge the pollen. Not all bees or other pollinators can perform this type of pollination, so flower species with tightly-held pollen rely on bees with this ability in order to be pollinated, and these bees have a secret source of pollen that others cannot access.
There are currently seven species of honey bees in the world, and they are all indigenous to Eurasia. The honey bees that we have in the United States, the European honey bee or western honey bee (Apis mellifera), are an introduced and domesticated species that we use for production of honey and pollination services. Honey bees live social lives, with a queen to lay eggs, female worker bees to forage, take care of the larvae, and build/clean the hive, and male drones to mate with the queen. Unlike bumble bees though, female honey bees will live through the winter, consequently a queen bee could have an average of 2-5 years of her reign.
Honey bees are kept domestically by farmers and gardeners to harvest the honey and beeswax, and to pollinate various crops. Commercial beekeepers bring their honey bee hives to farmers’ fields during their crop’s flowering time for anywhere from a few days to a few weeks to pollinate their crop. Some farmers even manage their own bee hives to have their own supply of pollinators and to harvest the honey in addition to their crops. In the United States, managed honey bees contribute nearly $20 billion dollars to the economy each year through their pollination services.
Credit: Wikimedia Commons