I suggest you read about Mason bees before jumping to any conclusions.
http://en.wikipedia.org/wiki/Mason_bee
There are probably multiple bees entering that space, because it leads to other chambers in which each bee can have it's space for their brood.
Mason bees are some of the best pollinators and are native to the Americas (unlike Honeybees which were brought from Europe). They are solitary bees, and rarely sting unless heavily provoked. They are also only active during a short period of the year, between Spring and Summer - so after a while you won't see them. Their brood however will remain in their chamber until next spring when they emerge.
I also wouldn't worry about them damaging your house. If you want to address the issue of them using that space as a home, you can manually remove the cocoons and store them; or wait until next spring once they emerge, and seal the area - though you will have a small window of opportunity to do this. Most likely the realistic alternative will be to manually clear the brood and seal it up, although if it were me I'd just let them be.
I think you are lucky to have large populations of mason bees, they are a great asset to have for fruit trees, gardens, and anything which requires cross pollination.
http://en.wikipedia.org/wiki/Mason_bee
There are probably multiple bees entering that space, because it leads to other chambers in which each bee can have it's space for their brood.
Mason bees are some of the best pollinators and are native to the Americas (unlike Honeybees which were brought from Europe). They are solitary bees, and rarely sting unless heavily provoked. They are also only active during a short period of the year, between Spring and Summer - so after a while you won't see them. Their brood however will remain in their chamber until next spring when they emerge.
I also wouldn't worry about them damaging your house. If you want to address the issue of them using that space as a home, you can manually remove the cocoons and store them; or wait until next spring once they emerge, and seal the area - though you will have a small window of opportunity to do this. Most likely the realistic alternative will be to manually clear the brood and seal it up, although if it were me I'd just let them be.
I think you are lucky to have large populations of mason bees, they are a great asset to have for fruit trees, gardens, and anything which requires cross pollination.
