Leafcutter Bees and Cows
What is the connection between leafcutter bees and cows, you might ask? This is one of those unique situations where, if you don’t know, you’ll never guess. But let’s take a minute to know who the leafcutter bee is first, before the big reveal…
The leafcutter bee (genus: Megachile) is a solitary bee found in many parts of the world and is an important native North American pollinator. In Florida alone, there are 63 species and 5 subspecies within 7 genera of leafcutting bees: Ashmeadiella, Heriades, Hoplitis, Coelioxys, Lithurgus, Megachile and Osmia.
Similar to mason bees in the way they nest, they don't live in groups or colonies. They use quarter-to-half inch circular pieces of leaves that they cut from trees and bushes to decorate and close off their nesting cavities. Some of the ornamental host plants they cut leaves from are ash, redbud, roses, azaleas and bougainvillea, which has thin smooth leaves. They prefer broadleaf deciduous plants and some species of leafcutters like to use resin and petals as well as leaves.
This 4:34-minute PBS video explains the connection between leafcutter bees and cows...
They like to construct nests in soil, plant stems, bamboo stalks or in wood holes made by other insects but also live in holes in concrete walls or empty shells of dead snails. They will nest in rotting wooden cavities, where they create cigar-shaped nests with multiple cells, each complete with a pollen ball for one larva to eat. Leafcutter bees overwinter in their solitary nests, and as newly hatched adults, they gnaw their way out of their nest in spring.
Some species have large heads and massive strong jaws for leaf cutting. They are similar in size to the honeybee (5-24 mm) and are strong, stout and black with white hairs covering the abdomen and thorax.
Leafcutter bees fly very fast and carry pollen on their abdomens, like mason bees, and are important pollinators of vegetables, fruits and many wildflowers. Some of these fast bees (Osmia spp.) are used by farmers in commercial crop pollination for alfalfa, carrots, onions and blueberries, in the same way the honeybee commercially pollinates almond trees.
The leafcutter can sting but is not an aggressive nest defender. If you get stung, it is far less painful than a honeybee sting according to the University of Florida’s Institute of Food and Agricultural Sciences. Simple logic: Respect their space and don’t handle them if you don’t want to be stung.
Don’t want these bees in your garden? They are beneficial, mind their own business and are no-maintenance. But their leaf cutting habits irritate people who seek perfection in their plants, although they don’t harm shrubs. If you want these bees gone, they don’t need a formal removal. You can set up a bee hotel at a distance from your plants to draw them away, or you can wrap your plants in cheesecloth to protect them, having cut away dead or damaged stems first.
Natural enemy parasitoids like some flies, ants, wasps and beetles attack their nests. Even the Coelioxys, a genus within the leafcutting bee family, is a kleptoparasite and will steal their nest, lay their own eggs and steal the stored pollen a leafcutter bee worked hard to gather.
Back to the initial question about the connection between leafcutter bees and cows. If you watched the video above, you already know that the alfalfa flower makes it hard for a bee to access its pollen, which is on a spring device. The bottom petal of the alfalfa flower is called the keel petal and is held closed by a thin membrane that creates a spring mechanism. When the bee lands, the membrane breaks and the reproductive structure flies up and slaps the upper petal or hits the bee in the face as she accesses the pollen. Yellow pollen is released and this process is known as 'tripping the flower.'
Most bees, including honeybees, don’t like being smacked and try to pry the pollen loose in other ways. Alfalfa, a legume, rewards she who risks a slap to access the treasure. The fearless leafcutter doesn’t seem to mind being slapped.
Pollinated alfalfa flowers create new alfalfa which becomes hay and is fed to dairy cattle. The logic is that if you eat ice cream you should thank the leafcutter bee for feeding the cow. While that may seem like a stretch, it is entirely true. Statistics show that the leafcutter bee trips 80% of flowers she visits while the honeybee only trips about 10%.
Either alfalfa pollen is delicious, or the brave leafcutter bee is just determined to get the job done so we can enjoy ice cream!
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