Like most bees, this leaf-cutting bee, Megachile brevis, is solitary, with each female building her own nest cells out of bits of leaves and petals without the help of a worker caste. These bees earn the name “leaf-cutter” from the leaves (and petals in the case of M. brevis) they cut to build their nests. This leaf-cutting bee is one of 59 species of Megachile in Colorado and can be found from the coast to coast. If you remember back to the Wonder of the Week from July 29, 2020, this bee, like its relatives, cut circular and oval shaped pieces from leaves and flower petals to construct their nests underground, in cast plant stalks, or curled leaves. All leaf-cutting bees belong to the Megachilidae family, which means “big-lipped family” in Latin. Notice the large mouthpart below the female’s eye in the image, this is a mandible. Mandibles with jagged teeth help her snip leaves and petals for her nest. We can tell roughly how long a female leaf-cutting bee has lived based on the wear of the bee’s teeth and if her wings are torn. Most members of the Megachilidae family can be recognized by the pollen-collecting hairs, called scopa, on the underside of their abdomens. The placement of the scopa is the main distinguishing characteristic for members of the Megachilidae family, as bees in other families carry pollen internally or on their hind legs. Megachilidae sweep up and hold pollen with their scopa. Fun fact, scopa means “broom” in Latin!
Megachile brevis can have up to four generations of offspring per summer2, and the final generation spends the winter in its nest as larvae. Nests are made of a series of cells, there may be as few as two or as many as 30 cells depending on space availability. Each cell is built out of leaves and/or petals and supplied with a food ball of pollen and nectar. The female lays a single egg on this ball and seals the cell, and her parental duties to that offspring are complete. Male bees do not assist in nest construction and die shortly after mating with a female. Bees, like many other insects, go through four major life stages: egg, larva, pupa, and adult (as pictured). The egg will hatch into a larva, which will feed on the pollen left by its mother. If winter is near, development stops here until spring. After the pollen ball is consumed, the larva will develop into a pupa. Pupae (plural) look like white, wingless bees and are very fragile and immobile. The pupae develop into adults, as pictured. The adults leave the nest and start the process anew.
Common name: Leaf-cutting bee
Scientific name: Megachile brevis (Family: Megachilidae)
Catalog number: UCMC 0126663 (female)
Label data: USA: Phillips County, Colorado; USDA field site - Ham4 CRP; July 30, 2013; blue vane trap, Adrian Carper, collector.
1. Scott, V. L., Ascher, J. S., Griswold, T., & Nufio, C. R. (2011). The Bees of Colorado. Natural History Inventory of Colorado, 23, vi–100.
2. Michener, C. D. (1953). The Biology of a Leafcutter Bee (Megachile brevis) and Its Associates. University of Kansas Science Bulletin, 35(3), 98.