These are probably the biggest bees I have seen on my travels
Violet carpenter Bees hibernate overwinter and they emerge in the spring, usually around April or May. Hibernation is undertaken by the adults in wood where there are abandoned nest tunnels. In the late spring or early summer, they may be seen around searching for mates and suitable nesting sites. After mating, the gravid femaless bore tunnels in dead wood, which is where the name Carpenter Bee comes from, although old nest tunnels may be used.
Like other solitary bees, the female creates the nest alone. The eggs are laid within a series of small cells, each of which is supplied with a pollen ball for the larvae to feed upon. The adults emerge in late summer then hibernate until the following year