Leafcutter bees are small to medium-sized, fuzzy insects that are a valuable part of the natural ecosystem because of the pollination service they provide to many plants. Unlike honey bees, leafcutter bees are solitary. They do not form colonies and each nest is the work of an individual female.
There are several species of leafcutter bees with similar habits and behavior. They nest in hollow plant stems and other natural cavities (including exposed gaps in building moldings and plywood house siding). The female leafcutter bees cut dime-sized, circular disks of foliage from nearby plants and place them within existing cavities to line and separate individual brood cells or chambers. A single female may cut as many as 10,000 foliage disks during her lifetime. The cells within the nest are each approximately 1/2-inch long and provisioned with a ball of plant nectar and pollen. One egg is laid in each cell. Leafcutter bee eggs hatch into small larvae ("grubs"). These consume the stored food as they grow and develop. After several weeks the larvae transform into adults and emerge from the hollow stems or structure gaps
The most easily recognized symptom of leafcutter bee activity is the circular holes 1/2 inch or less in diameter cut from the edge of ornamental plant leaves and flowers. The cuts are very neat and nearly perfectly round, leaving the appearance that the holes were “punched out” with a large paper punch. The holes are cut from the edge of the leaf or flower and never from the interior.
Commonly attacked plants include roses (both foliage and flower petals), redbud, lilac and ash foliage, though other plants may be attacked as well. The damage is a curiosity rather than a threat and controls are rarely justified. The bees are beneficial pollinators and should be encouraged and protected rather than controlled through wide-area use of insecticides.