The following is an excerpt from the August 2015 Bee Mail put out by our friends at Crown Bee:
Right now mason bees are in a critical development phase.
In a normal summer:
Spring mason bees should be beginning a final development from larva to adult bee. If you were to open a few cocoons right now, you’d normally find legs just forming and the bees would be all white. (The photo is about right for a “late-August” phase.) Bees need summer warmth to develop correctly. If it were too cold, your spring bees wouldn’t develop into adult bees in time for winter hibernation.
ALERT- What happens with a warmer-than-normal summer:
With too much heat, development speeds up. Your mason bees become “complete” adults too soon and begin to consume their internal stored fats much sooner. As it is very warm, their metabolism is high and their consumption of stored fats is accelerated. Very likely these bees may run out of this life-preserving “fuel” mid-winter and die.
In the Pacific Northwest where Crown Bees is headquartered, we have enjoyed a wonderfully warm summer and as a result, I’m very concerned about our mason bees. You should be as well.
What to do:
If in the Northwest, place all of your developing mason bees someplace cooler, like the north side of your house, in a cool garage, or similar. Don’t place the bees into a refrigerator yet, but do have them in a cooler environment between 60-70°F. Do not ignore me on this. Northwest temperatures have been 10-15°F (5-9° C) higher than normal and I believe next year’s bees are in jeopardy today. If your summer temperatures haven’t been that much above normal, than you can ignore my cautionary words. If you share my concern after reading this, open up one of your nesting holes (tubes/reeds/trays) and carefully cut open one of the cocoons located towards the front mudded end. This cocoon should hold a male that has lesser value than females. If the bee is white, most of your bees are likely on par in terms of development and should be fine. If the opened cocoon contains a black or brown bee then find a cool place for all your bees to rest until harvest.