Megachilidae – Leafcutter and Mason bees

MEGACHILIDAE:

LEAFCUTTER AND MASON BEES

Nesting Preferences

Mason Bees: The females build their nests to house the larvae and typically prefer to use mud to construct the nest
Leaf-Cutters: The female leaf-cutter bees also build nests to house their larvae but instead construct it out of leaves. 
Both: Both mason bees and leaf-cutter bees tend to create their nests in wood rather than nesting underground. It is important to note that both of these types of bees do not usually bore into woods like carpenter bees. Instead, they nest in holes already drilled by woodpeckers or other insects. They may also utilize rooted pithy stem structures that are partially hollow.

Population and Pollination

Population numbers are higher in the western states, especially the blue orchid bee. This bee is very important for the pollination of fruit trees and in particular, sweet cherries and almonds. Interestingly, megachilidae bees do not carry pollen on their back legs but rather on the underside of their abdomens. In these western states, farmers are now providing drilled boards as nesting sites to promote bee recruitment. However, both types of bees have ranges that extend into Georgia. 

Megachilidae in Your Garden

Mason Bees: If you want to know if you have mason bees in your garden, look for evidence of nesting sites. Just like leaf cutters, they have an unusual brood cell method. Again, utilizing hollow pithy stems that have been bored out by other insects, mason bees pack their nests with mud/clay/chewed plant tissue. The pollen and nectar is then deposited in the nest and the egg is laid on top. The bee than creates a partition of mud which doubles as the back of the new cell. 
Leaf-Cutters: You will most likely know if you have a leaf cutter bee in your pollinator garden when some of the leaves on your plant begin to display characteristic patterns where circles have been punched out on the leaves. The bee will then use this leave material to build its nest, hence the origin of their name. They collect the leaves to create individual nest cells lined with the cut leaf cut and fill it with nectar and pollen. The egg is laid and the cell is then closed. She then repeats this process throughout the tunnel, producing a series of tightly packed cells. 
A finished nesting tunnel may have a dozen or more cells inside a tube that is 4-8 inches long. See the video to the right to witness a leafcutter bee creating a brood cell inside a wooden tunnel built with a plexiglass portion for viewing. 
 

FEATURED MEGACHILIDAE:

BLUE ORCHARD BEE

General Overview:

The blue orchard bee(Osmia lignaria) is an important member of the Megachilidae family. It is a mason bee that is very economically important for fruit that blooms early in the spring within Canada and the United States. 

Personality:

Orchard mason bees, like all mason bees, are very shy and will only sting if they perceive serious danger. The stinger is actually an egg guide. Because of their docile behavior, mason bees are preferred by people who desire pollination in urban settings. 

In Your Garden:

If you would like to keep and cultivate blue orchard bees in your pollinator garden or growing area, it is important to know that this species is divided into two subspecies(O. lignaria propinqua and O. lignaria lignaria). The division is set around the geography of the Rocky Mountains. USDA entomologists have strongly suggested that these species be kept to their native origins:
               * Osmia lignaria propinqua (West of the Rockies)
               * Osmia lignaria lignaria (East of the Rockies)
So, only purchase Osmia lignaria lignaria species for your garden and help keep the mason orchard bee where it should be!
See the blog page here for instructions on how to create your very own bee box for nesting leafcutter and mason bees.