Wednesday, May 29, 2013

Cutter Bees


We've had several residents notice that "something" is eating their plants or trees and they're requesting information as to what is happening.  Damage looks like this photo:
 


This smooth semi circle is a result of the Leafcutter Bee.  Here's some information from a recent google search:


Leafcutter bees are important native insects of the western United States. They use cut leaf fragments to construct their nest cells. They often are essential pollinators of wild plants


Most common leafcutter bees (Megachile spp.) are approximately the size of the common honeybee, although they are somewhat darker with light bands on the abdomen. They also have different habits. Leafcutter bees are not aggressive and sting only when handled. Their sting is very mild, much less painful than that of honeybees or yellowjacket wasps.
Leafcutter bees are solitary bees, meaning that they don't produce colonies as do social insects (honeybees, yellowjackets, ants, etc.). Instead, individual female leafcutter bees do all the work of rearing. This includes digging out nesting areas, creating nest cells and providing their young with food. Adult females may live up to two months and lay some 35 to 40 eggs during this time.
Leafcutter bees nest in soft, rotted wood; thick-stemmed, pithy plants (e.g., rose); and in similar materials that the bees can easily cut through and excavate. Nest tunnels may extend several inches deep and coarse sawdust may be deposited at the entrance. This sometimes causes confusion with other wood nesting insects such as carpenter ants. However, leafcutter bees restrict their tunneling to soft, rotted wood and do not cause damage to homes or other wooden structures.

After the nest is made, the bees collect fragments of leaves to construct individual nest cells. The bees cut leaves in a distinctive manner, making a smooth semicircular cut about 3/4 inch in diameter from the edge of leaves.  This injury often is only a minor curiosity.

Leafcutter bees do not eat the cut pieces of leaves that they remove. Instead, they carry them back to the nest and use them to fashion nest cells within the previously constructed tunnels. Then they provision each leaf-lined cell with a mixture of nectar and pollen. The female lays an egg and seals the cell, producing a finished nest cell that somewhat resembles a cigar butt. A series of closely packed cells are produced in sequence. A finished nest tunnel may contain a dozen or more cells forming a tube 4 to 8 inches long. The young bees develop and remain within the cells, emerging the next season.

Insecticides are ineffective for preventing leaf cutting. The only known control of leaf injuries is to cover susceptible plants with cheesecloth or other loose netting during periods when leafcutter bees are most active.


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