I have Mason bees in my window sills. They face south. Still have not emerged. Remember it is a La Nina year so our temps overall have been a bit cooler. And my guess is that maturity is temperature averaged. Honeybee on the other hand, are all ready to go and any time there is good weather they can pop out and pollinate. On a side note yesterday I saw my first bumblebee. Huge and hovering around looking for a nest. No doubt a queen.

Mine get moved so even though mine started emerging it's probably a result of placing them away from recent cold nights and close by the house. The bees I see on plums have been everything but the honeybees in the last several days. 

My guess is that emergence is a decision and less a progression towards maturity. With the exception of social like insects such as honeybees mason bees are cold and emerge from dormancy, so I can't imagine development not being fully completed during the seasons ending period and during plant senescence. 

I look at it this way that Alaska has cold blooded pollinators, the moths, and solitary bees too but I figure there could be some form of low temperature estimation of when to wake up much the same as trees and other plants. 

Here's a link that might be interesting:

site:gi.alaska.edu "three consecutive days is 50 degrees"