Have you ever looked at a perfect specimen of a plant, only to discover that some insect has disfigured it by cutting circles into the leaves? Were you dismayed, or angry that some nasty insect was chewing on your plants? When I see circular gaps missing from the leaves of my plants, I rejoice! Those perfect little circles mean that leafcutting bees (Megachile spp.) have visited my garden. Far from being upset by the disfigured leaves, I am overjoyed that bees feel safe and comfortable in my yard.

In addition to the hive-dwelling honeybee, which was introduced to North America by European settlers in the 1600's, California supports 1,600 native bees. Most native bees are not social, coming together briefly only to mate. Unlike honeybees, seventy percent of native bees nest under the ground, and thirty percent live in cavities above the ground. While honeybees are integral to the pollination of commercial crops in the United States, our 4,000 native bee species pollinate most of our native plants, such as pumpkins, blueberries, cherries and cranberries. Native bees evolved alongside native plants, and the timing of their foraging (and subsequent pollinating) coincides with the bloom of the plants. Native bees pollinate seventy-five percent of nuts, fruits and vegetables, in the world, and eighty percent of flowering plants. They also forage longer than honeybees, and are more able to tolerate cold weather and windy conditions.

The leafcutting bees who leave circular holes in my plant's leaves belong to the family Megachilidae. There are at least 75 species of leafcutting bees inhabiting California. These bees live an abbreviated lifespan. They emerge in spring or early summer, and mate. The females spend the next several weeks preparing their nests. They forage for nectar and pollen for their own sustenance, but also to create a “bread” mixture with which to stock their nests. The females find an empty crevice, such as a hollow twig, or tiny tunnel abandoned by another insect. She then uses her unusually large jars to chew circles from leaves to line the crevice, creating a soft home for her offspring. She deposits a lump of the “bread”, and one egg, then seals the cell with more leaf circles. She will continue to stock and seal individual cells along the length of the crevice. The egg hatches, and the larva consumes the food left by its mother throughout its larval stage, then pupates and emerges as an adult in the spring/summer, to repeat the cycle.

Some gardeners have trouble accepting the disfiguring circles leafcutting bees leave in leaves. Placing cheesecloth over the plant of choice, and filling crevices, which may be potential nesting sites, with a couple drops of white glue can dissuade the bees. I, however, will continue to have a quiet, personal party each time I see those holes in my leaves!