By Amy Yarger, Butterfly Pavilion Horticulture Director
Imagine you are enjoying an evening stroll in your neighborhood and stoop to smell a vibrant pink rose. All of a sudden, your attention is drawn to the rose’s leaves, which look like someone enthusiastically took a hole puncher to them. Now, for those people who aren’t thinking about bugs all the time, it might go something like this: “What a shame, some destructive insect is chewing up these roses.” But for those of us in the know (which now includes you!), we see those perfect little cut-outs and think, “Oh boy! Leafcutter bees are nesting nearby!” If you are really enthusiastic about pollinators, this discovery might just make your day.
Leafcutter bees (Megachile spp.) are important pollinators of an extensive gamut of commercial crops, including alfalfa, carrots, onions, blueberries and cranberries, among many others. Leafcutter bees are also responsible for pollinating a prodigious range of wildflowers and garden flowers. They are appealing and charismatic solitary native bees, a little more than a centimeter in length and with broad heads and bodies. Some species in the genus can reach the size of honeybees but tend to be grayish in color instead of tan. The best identifying characteristic, however, is the set of brushy hairs on their abdomens called a “scopa” – these bees carry pollen on their undersides instead of on their legs like bumblebees and honeybees do. When they have a full load, their abdomens are covered in bright yellow pollen – probably the only time the term “yellow-bellied” is used to mean something positive!
The female leafcutter bees have sharp jaws to cut uniform semi-circles of leaves to make brood chambers for their young. Even though these pollinators are busy all summer long, evidence of leafcutter bees is often seen more than the actual insect; these bees use rose leaves and others to line and partition their nests, which are usually found in cavities in the ground. The female bee then provisions her nest chambers with pollen she collects from flowers, most often flowers in the sunflower family. Once the bee larvae hatch, they have all their food ready for them as they grow, thanks to the pantry stocked by their prepared mom. Leafcutter bees are also known for their fast, fluid flight, and some entomologists have compared them to fighter jets. Another behavior you might notice when they are foraging on flowers is how they will lift their abdomens up to the sky, in a move I like to call the “perky rear”.
Leafcutter bees are found throughout the meadows, prairies and plains in western United States, often on plants such as sunflowers, blanket flowers, asters, coneflowers, alfalfa, and clover. All adults need nectar as fuel, but only females collect pollen for their young. These bees need frequent, connected habitat patches to be able to survive. Most solitary bees can’t forage at distances larger than 600 meters, and unsuitable or poor habitats in between can be a barrier to finding the next habitat patch for these tiny pollinators. There are lots of ways to help leafcutter bees find healthy habitat, though. You can advocate for more habitat patches in your community and plentiful natural areas where leafcutter bees and other solitary bees can nest safely in the ground. Planting summer-blooming native perennials, such as blanket flowers and coneflowers, will ensure bee moms have a plentiful pollen supply. And finally, just by understanding that gardens don’t have to be perfect to be beautiful, that helps leafcutter bees…and people, too!
Want to learn more about pollinators and how to help them? Contact Butterfly Pavilion’s horticulture department at habitat@butterflies.org!
If you see this pollinator or others around Baseline, take a picture and upload it to Baseline’s iNaturalist page. By doing so, you can be a citizen scientist and help track the diversity and volume of pollinators at Baseline.