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Old 11-26-2011, 01:05 AM   #6
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Join Date: Nov 2008
Location: Wisconsin

Originally Posted by turttle View Post
So if no human is providing fancy bee houses with straws in them, where do mason bees nest? If I have snags in my woods, can I safely assume there are probably enough holes in them to keep the bees happy, assuming they nest in wood (given they tell us to drill wooden blocks for them, that seems logical but I don't know much about them)?

I have mason bees in my flowers in the summer, so they are around somewhere. How far do they fly for food - miles like honey bees do, or do they stay closer to home?

I never knew there were so many kinds of native bees until the last few years when I started really looking and wondering what was flying in my yard. Very cool critters.
There are thousands of species of bees; over 4000 in North America alone. My state, Wisconsin, has documented over 400 native species. Several different species are referred to as mason bees, a group that uses mud in the construction of their nests.

Most of the bee species are solitary (don't nest in colonies with worker bees) and most are ground nesters.

Osmia lignaria has several common names; blue orchard bee, orchard mason bee, and sometimes just mason bee. The adult form is present only for a short time during the spring. They nest in holes in trees, sometimes inside broken stems of large grasses, and really just about any kind of material that has holes about 5/16 inch diameter.

Snags will often have holes for mason bees to nest in. They might be abandoned beetle holes or any other kind of wood boring creature's hole. Trees damaged by weather events may also contain places for bees to nest. A lot of nesting sites are destroyed when people remove snags and weather damaged trees.

As for providing bee nesting sites, leaving snags and weather damaged trees is a good natural way to go. But a lot of land owners won't have that option, or won't want to wait that long to provide nesting sites.

As an alternative to nesting blocks/straws/trays, holes can be drilled in wood fence posts, dead trees, tree stumps, logs in brush piles, etc. Don't drill holes in treated wood. 5/16 inch diameter holes are the preferred size for mason bees, but smaller and larger diameter holes will provide nesting sites for some of the many other above ground hole nesting species.

Osimia lignaria are believed to range up to about 100 yards when foraging. If the distance is greater that that, they will usually look for new nesting sites closer to their sources of pollen and nectar.

Cool critters and pleasant to observe. Since they haven't 'put all their eggs in one basket' like honey bees do, they don't choose to defend their nests. If they sense danger at their nest site their survival strategy is to just move to another nesting site.
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