Many people have heard of leafcutter ants carrying bits of leaves around the forest like little parasols. Ants are all in the family Formicidae, in the order Hymenoptera, which includes bees, wasps, and ants. Leafcutter ants do not eat the leaves, but rather compost them to feed their fungus gardens. They only eat a particular species of fungus, removing all other species, and constantly tend their gardens to keep them clean.
Photo: Peter Oboyski
Leafcutter bees (family Megachilidae), although they also belong to the order Hymenoptera, use leaves very differently. Just like the ants, they cut out little disks from leaves, but then fly off holding them in their mouths. They use these leaves to line the walls of small holes and cracks they find in the ground, wood, stone, and other materials. They then fill the nest with a mix of pollen and nectar they collect from flowers, lay an egg alongside the ball of food, and seal off the nest cell. When the egg hatches the larva has all it needs to survive until adulthood with no other input from their parents or siblings. The walls made out of leaves not only form the bedroom in which the larva grows, but also helps maintain the proper humidity, giving off moisture as they dry or absorbing excess moisture if the environment is too wet.
Because leafcutter bees are constantly building new cells to produce more offspring, they are constantly visiting flowers for pollen and nectar to provision these larvae. This makes them important pollinators. Many of the labels from the Essig Museum specimens include the name of the plant (or host) a bee was visiting when it was caught.
Not all bees in the family Megachilidae use leaves for their nests. Some use soil and clay and are called mason bees. Others collect animal hairs and plant fibers and are called carder bees. As spring time roles around the new adult bees are emerging from their leafy nests and starting to build homes for their children. If you want to encourage these important pollinators in your own backyard you can provide nesting sites for them by drilling different size holes in a block of wood and setting it on the ground or up in a tree in an out of the way location. Then keep your eyes open for little pieces of leaves flying by.
– Peter Oboyski, Collections Manager & Curatorial Supervisor, Essig Museum of Entomology