Mason Bee Life Cycle

                                                          illustration © Glen Buschmann 2009
• Top - cocoons (adults inside)
• Middle - larvae feeding on pollen
• Bottom - eggs laid on pollen

The Bee - - Bee Activities
Fall / Winter
      Adults, sleeping
By September the bees are adult in their self-made cocoons. Here they remain, dormant and maturing, until late winter / early spring.

January / February
      Adults, waiting
The bees are now fully mature and waiting for warmer conditions before emerging from their cocoons. If brought into a warm room, they will emerge within a few hours, especially as the season moves into February.

March - June
      Adults, working
As the weather warms, a few male bees emerge from their cocoons; they feed on nectar and lurk at the nests. In time more males emerge, and then females. The males pounce, the bees mate. Mating complete, the female orients herself, eats, and selects a suitable nest site. She builds and provisions a cell and lays the first of 25 to 30 eggs, (one egg / cell each day). The bees in April and May are very busy; by June the adults are finished and all dead.

April - June
      Eggs and Larvae, eating
The eggs hatch about a week after being laid. It takes four weeks after hatching to eat the food mass. Feeding done, they spin a cocoon around themselves and move to their next stage of life.

June - September
      Larvae to Adult, morphing
Inside the cocoon the bees completely transform over the course of the summer, progressing from final larval stage to pupae to adult. The bee is very fragile during these significant changes.
The Beekeeper  -- Keeper Duties
Fall / Winter
      Store - Inspect - Clean - Build
By October the bees should be moved into unheated winter storage. Fall is also the time to inspect nests and clean any loose cocoons.

January / February
      Prepare (for adult bees)
New housing needs to be ready.  Place the bees in their springtime location before fruit trees blossom, (mid Feb to mid March) - ideally a sunny, protected, south or southeast facing wall. 

      Observe - Enable (adult bees)
For the bees, this is a time of frenzied industry; for the beekeeper it is time for observation and some service.  Make mud available for females building their cells.  (Not too sandy / silty.)  Nest tunnels with some bold patterns and asymmetrical sizes or are easier for bees to track.  More housing can be added through mid-April, but don’t rearrange existing nests. Watch the bees, note what flowers they visit and what nest tunnels they prefer.  And, enjoy.

April - June
      Protect - Observe (eggs and larvae)
The young within their cells are somewhat safe. Don’t jostle the nests - hard hits can dislodge the larvae and break the mud walls. Good management limits pests, from tiny wasps and mites to woodpeckers.

June - September
      Manage - Ignore (nests)
The sealed cells can be ignored until fall. Or, you can move new nests into winter shelter, (unheated, but away from storms). Protect from pests with fine netting. Handle gently - pupal bees and mud cells are both delicate.

Bees, Birds, and Butterflies
PO Box 11464    Olympia, WA USA    Glen Buschmann, 2008, 2013, 2016


  1. I'm in Lacey. I put up a shelf on the east wall. I have more new bee blocks than the neighborhood needs for the season. I have about a hundred ? cocoons from last year and
    3 blocks of cocoons. I'm thinking about putting the blocks and cocoons out in intervals: one old, one new, maybe wait until a block is full before putting out the next new block ? Or placing them weekly through March. There won't be enough blossoms in early march for all the bees. What do you (all) think ?

    the word verification is not clear

  2. Thanks for the comment. I've rewritten a bit of the language. The "rules" page goes into more detail. This page is better seen as a grid and I haven't done that for the blogpage.

    Mason bees emerge over the course of several weeks even if all the nest blocks are put out at the same time. Unless I need some bees for teaching I put all my mason bees out at once. How many? -- provide enough housing for the capacity of the GARDEN and NOT for the capacity of your Mason Bees. You have to decide how much is enough, become cold-hearted. They are so easy to raise (if you do everything right) that within a few years their numbers can easily exceed the capacity of a garden, both stripping pollen resources and overwhelming natural nest sites that later solitary bees need. Depending upon the spring weather I may put out another CLEAN block of nest tunnels in mid April. Then I put out a nest block in late May made for OTHER tunnel nesting bees; late season solitary bees often prefer smaller diameter holes.


  3. I will follow your example and put out new blocks (with parchment) in mid April and late May. There was
    leaf cutter activity here last year
    and some leaf cutter cocoons in with mason bees.

    Anyone know of annuals that will offer pollen to mason bees ?

  4. Annuals are few for mason bees, as most annuals are not in bloom until summer. There are a number of biennials that overwinter and bloom in the early spring (and sometimes called "winter annuals". I let kale bolt in the spring and bees are all over it; other mustard family plants are equally popular. Our blog has several posts under the label "Pollen and Nectar". Also, check out the Xerces society for plant suggestions. Glen