Mason Bees

Does anyone have experience with artificial habitat and Mason Bees? Specifically I'm wondering how many bee houses or bore holes would be ideal for a 10' x 30' garden. Does it matter if all the holes are in one block or should I spread the houses around the garden? I know I should have a source of mud near by and to place the structure off the ground facing towards the morning sun. Any feed back would be appreciated.

I will be experimenting with a native bee box myself this spring.  From my understanding, 'mason' type bees are one of many types of native bees.  They use mud to cap the entrance to their solitary den, usually in a wood block.  There are also dozens of other native bee species that use holes in wood, and undisturbed, hard dirt to make their homes in.  Apparently, the ground dwelling type doesn't like moist or rich soil as well.  All the more reason to have areas of drought tolerant perennials in our yards! 

Most native bees are solitary, and not honey collectors.  Bumblebees do live in small colonies, however. 

I found a ton of useful information at the following resources:

http://attra.ncat.org/attra-pub/nativebee.html
http://www.xerces.org/wp-content/uploads/2008/11/nests_for_native_bees_fact_sheet_xerces_society.pdf
and www.xerces.org in general. 

This guy makes great stuff for mason bees.
http://www.etsy.com/shop/andrewsreclaimed?section_id=5812141

Retread, I've been keeping my eye out for mason / native bee information since you posted your question.

This website http://www.crownbees.com/ has a lot of really good information about mason bee care, and potential problems.  They also sell mason bees and equipment, but their main concern appears to be promoting information about mason bees, not just selling.

In particular, they recommend the use of small cardboard tubes or straws to serve as the mason bee homes, rather than holes drilled in a wood block.  Apparently, there are many potential parasites that can invest their cocoons throughout the winter.  Bees emerge in May, and are done laying their eggs by July, giving pests such as mites, other parasitic bees, mold spores, etc etc. many months to infest the next years' brood. 

Using tear-able cardboard allows the diligent gardener or orchard owner to harvest and store desirable cocoons for the following year, and discard any pests that might have accrued.   

I'd love to hear how your native bee endeavors pan out this spring!

Crownbees is a great site. Besides inserts or cardboard tubes, stackable wooden or plastic trays are a good way of providing habitat while allowing for pest control.
I compiled a summary of the most pertinent information that I hand out to interested folks.