Leaf-cutter Bees

Photo by: Bryan Reynolds

Megachilidae

Megachilidae is a family of bees, more commonly known as Leafcutter bees.  Some genera within this family are known as mason bees and others wool-carder bees. These common names refer to their habit of constructing burrows, with mud and plant resin (mason), with pieces of leaves (leaf-cutter), plant-hairs (wool-carder). This family of bees is widely distributed across North America.

Leaf-cutters are morphologically distinct from the usual run of bees, thicker than most species and predominantly black. Some abdomens are completely back, yet others are are patterned with yellow patches or stripes. Female Leaf-cutter bees carry pollen on the underside of their abdomen, using hairs called scopa (a trait that distingusihes Megachiles), and this is why Leaf-cutters often appear to have gold underbellies when photographed. This family ranges in size from half a centimeter long to 2.5 centimeters long. Their wing tips are black, along with their antennae.

Leaf-cutter bees are gentle bees, typically, they will only leave a slight sting if handled. They often come into closer contact with humans than most pollinators, because of their habits of leaving holes in garden plants to build their nests. That’s right, nests! A common myth is that they eat leaves – definitely not! Nest structures are usually made in pre-existing cavities and are modified with mud, resin, and leaf fragments.

Megachilidae family are considered solitary bees and do not form hives or colonies. Female bees look for a mate in spring and summer (these bees are visible between March and October). After fertilization, the female stores eggs in individual cubbies within a nest. You can think of each female as a solitary Queen. Each egg is given nutrition and sealed away until it hatches. The males don’t have to live under monarchical rule, though. Males die almost immediately after fertilizing the eggs.

Written by: Robert Gibson, an undergraduate Environmental Studies student at the University of Oklahoma