Signs of Spring 8: Mason Bees!

Photo by B. Moisset, Wikimedia Commons

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Mason bees (Osmia spp.) are solitary bees that have very short life spans (only six weeks or so). These bees nest in tubes or holes and have earned the name “mason” because they build wall-like partitions made of mud inside of their tubular nests. A mason bee gathers pollen and nectar from the flowers that are blooming during its short life and packs it around the eggs that it lays in the mud-wall partitions of its nest. A mason bee may fill up more than one nest with its eggs and its accumulated nectar and pollen.

The eggs then hatch into larvae that feed on the stored food and steadily grow and develop. The nest walls are extremely important here because they keep each larvae isolated with their own food supply! The mature larvae then spin cocoons and develop into pupae which will, still inside the cocoon, then molt into their adult forms. It is inside of this protective and insulating cocoon that the mason bee overwinters. In the spring, male mason bees emerge first and wait outside of the nest for the later emerging females. As the females emerge, the males immediately mate with them. After they mate, the males die, and the females then find a suitable tubular structure for its nest and begin to lay eggs, gather nectar and pollen, and, as a great ecological tie-in to this activity, pollinate many different species of flowering plants.

Photo by D. Sillman

Last Fall an old friend (and regular reader of this blog) gave me a beautiful, tear-drop shaped, bamboo basket of sealed up mason bee tubes. My instructions were to put it somewhere where it would stay cold all winter and to watch it carefully until Spring finally arrived. I hung the basket in my unheated garage and admired it regularly whenever I went down to get into my car.

The tubes remained quiet all winter, but suddenly, two weeks ago, they became active. A sticky, powdery dust layered out on my bicycle (which was parked right below the basket). Tiny holes showed up in some of the tube-sealing materials, and a small mason bee somehow flew up through the garage ceiling (maybe through the cold air return?) and ended up in my bedroom where I found him, immobile and, very sadly, deceased.

Outside our endless winter was still going on. Cold and snow and no flowers or nectar or pollen for the little bees. I had failed them and let them emerge too soon to survive.

Or so I thought!

Last Thursday it was sunny and 70 degrees. My forsythia along the driveway had started to flower a few days before. I opened my garage to work on my bicycle (a ride down on my local trail was actually possible that afternoon!). As I stood in the opening of the garage and let the sunshine pour in, I saw movement on the floor: mason bees!

The bees were exhibiting a vigorously positive phototropism and were moving slowly but steadily toward the sunlight. At first there were just a handful of them, and I gently picked each of them up and deposited them in the sunshine underneath the branches of the forsythia. Then there were more of them: ten, twenty, thirty, forty or more mason bees walking very zombie-like toward the sunshine.

Close up of mason bees in tubes

Photo by D. Sillman

When each bee got an inch or two into the sunny section of the garage floor they stopped as if stunned by how good the sunlight felt! They then wiggled their abdomens, groomed their wings with their legs, fluttered their wings and then, after two or three minutes of warming up and cleaning the garage dust off of their bodies, they launched themselves into the air. None of them flew very straight or with anything that resembled skill. They careened to the right or to the left and smacked into the wheel of my bike, or into my leg, or into the concrete block of the driveway wall. After they landed, though, they picked themselves up, readjusted their wings and then re-launched themselves into the air.

I watched at least twenty-five of the bees take their first flights. Often they would cycle back toward the garage before they finally found the forsythia. They frequently landed on my pant leg or on the top of my shoe before flight 2.0 ensued. Almost all of them, though, eventually ended up in the branches of the forsythia.

Photo by D. Sillman

I put the tube basket out in the sun next to the forsythia. As it warmed up I could hear scraping inside of the some of the still sealed tubes. A tiny flutter of powder began to float down in front of the basket. More bees were going to emerge! When I went back down to check on the basket after going up to my computer to write all of this down, there were active mason bees (the males) on the tube basket poking at the still sealed tubes. The scratching inside the tubes was even louder than before! The females were about to emerge!

An hour later the females were emerging from their tubes. The males were right there to mate with them and nature was taking its course!

I can’t tell you how much better I feel now that my mason bees survived my inept care! The very slow start to the spring made the timing of their emergence a very delicate thing. I am glad that they survived in the garage in their zombie-cold state, and I am very glad that the forsythia flowered in time to provide them a source of food. Survival is never guaranteed even with an abundance of clumsy human help: there are hungry birds waiting to pick off slow flying bees, there are old spider webs around the edges of the garage and up in the branches of the forsythia, and we had snow showers all day on Tuesday and today (Thursday) it is snowing again! There must be dozens of fatal traps lurking out there that could abruptly end this apian experiment.

The bees, though, are moving ahead as fast as they can! Here’s a video of them that Deborah made!



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2 Responses to Signs of Spring 8: Mason Bees!

  1. Paul Hess says:

    Bill, this is one of the most fascinating and delightful essays I can remember reading on your blog. I had no idea about this complex behavior.


  2. Schrefflers says:

    We love this piece. What joy for the two of you!! Very well done: captured and held our interest and we have questions!

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