Friday 5: 5 Steps to a Native Bee Cavity Nest

I quite enjoyed writing the bee nest cap post last week, so I’m going to do another Friday 5 about my bees!  This week I am focusing on how the bees (Megachile sp.) are making their nests.  It involves these 5 steps:

1. Find a cavity

finding nest

Finding a nest

My bee house was designed to provide cavities to attract native cavity nesting bees and it seems to being doing its job!  At any given time in the last month, there have been bees looking for nesting sites.  They fly around in front of the bee house (like the bee in the lower center of the photo), find a cavity that looks good, and crawl inside to inspect it.  If it is acceptable, they fly off and start gathering nesting materials.  If they don’t like it, they fly around and look for a better cavity.

2.  Build and provision a cell

building a cell

An incomplete cell

After a suitable cavity is selected, the bee starts building cells in her new nest.  She flies away from the nest and returns a few minutes later with leaf bits, small rocks, and globs of resin in her mouth.  She crawls into the nest head first and starts plastering the walls with the nesting materials.  On most trips into the cavity, she carries a load of bright yellow pollen on the underside of her abdomen.  Presumably, she deposits the pollen inside the cell for the future larvae to eat because the bees nearly always come out of the nests clean.  When the cell is about 8 – 10 mm long, they move on to the next step.

3. Lay eggs

laying eggs

Bee looking out after laying eggs

After a cell is completed, the bee crawls all the way out of the nest, turns around, and backs into the nest.  She spends several minutes inside the nest laying eggs in this position.  When she’s done, she crawls to the front of the nest, pauses for a minute or so, and flies off to start gathering nesting materials for the next step.

4. Cap cell and repeat

capping a cell

Capping a cell

When the bee returns to her nest after laying eggs, she appears with more nesting materials in her mouth, but no pollen.  She then builds a cap for the cell in which she has laid her eggs using the nesting materials.  There is a similar wall between every individual cell within the nest.

The bees typically make about 8 cells in the cavities in my bee house. Once a cell is sealed, the bee starts a new cell, lays more eggs, and caps the new cell.  It’s taking my bees 2-5 days to complete all of their cells, depending on the diameter of the hole and the length of the cavity.  The bigger the diameter, the longer the bee takes to build her complete nest.

5. Cap nest

building a nest cap

Building a nest cap

When cavity is nearly full of cells and there is only about 0.5 – 1 cm of the cavity still empty, the bee starts to build her nest cap.  She carries leaf bits, rocks, and resin to the nest and starts packing the materials in front of the last cell, often leaving a space between the last cell and the nest cap.  She starts building with a mixture of what is apparently leaves and saliva, then starts adding sand, rocks, and resin closer to the end of the cavity.  Depending on the nest cap type she builds, the bee may build out beyond the cavity 3 – 5 mm, but many of them are finished flush with the edge of the nest.  Most of the bees start a new nest almost immediately after finishing one, often moving into the next closest available and suitable cavity.

I have to say that I’m rather addicted to watching my bees.  I gave myself a sunburn one day because I was out photographing the bees building their nests for so long.  Another day I stepped into one of the many ant nests in my yard because I was so absorbed by the bees (have I mentioned lately that ants and I don’t get along?)  One day it was so windy I was worried another branch like the one I used to build my bee house would break off the tree and smack me in the head.  Still, I go out every day and watch.  I’m mean really, who can resist this?:

giant resin glob

Giant resin glob!

Look how big that resin glob is compared to the bee!  Anything that puts so much work into building a nest while looking so darned cute is alright in my book.  :)


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