Leafcutter Bees

     One summer day I noticed several semi-circular, three-quarter inch holes on the edges of a few leaves of the red bud tree in our back yard.  I knew pieces of the leaves were cut off and carried away by leafcutter bees, but I didn't know details why the bees cut them so I did a little research.
     Leafcutter bees are native to much of the United States and important pollinators of flowers.  They are solitary nesters, not aggressive and have mild stings.  They are about the size of honey bees, but dark with white or silver hairs.  Females' abdomens have dense brushes of hairs that carry pollen from the blossoms to the bees' nests. 
     Each female leafcutter nests in soft, rotted wood or in the stems of large, pithy plants such as roses, which we have in our yard.  The pithy insides of some of our rose stems are exposed to the outside because of pruning, giving female leafcutters easy access to the inside of the stems. 
     The nesting tunnel of each female leafcutter bee may be several inches deep.  She cuts out each semi-circular section of leaf with her mouth parts to make rolled-up nest cells with those leaf parts in the burrow of wood or pith.  She places a mixed ball of nectar and pollen in each leafy cell, lays an egg on it and seals each cell with a round piece of leaf.  Each cell resembles a tiny cigar butt and those cells are in a closely-packed series of a dozen or more in the tunnel, though a female leafcutter bee can lay up to 40 eggs.  The larva in each little chamber eats its provision of nectar and pollen until the food is gone, pupates in its cell and emerges the next spring as an adult male or female bee.
     Leafcutter bee species live all over the world.  There are about 140 kinds in North America.  Most of us don't see leafcutter bees, but we can more readily spot their interesting rounded or semi-circular works on thin, deciduous leaves of several kinds of trees and shrubbery, including on our lawns.