|Some of the surprises in our yard|
We moved last fall, after the flowers had finished blooming. So these lovely spring days have been full of surprises as we work in our new yard. Rhododendron and azalea bushes are breathtakingly colorful. Mounds of snow-on-the-mountain fling the whitest of snowdrifts against the somber evergreens. A mix of ground covers fill drab areas with violets, primroses, forget-me-nots, lilies of the valley, and other bloomers. Tulips and irises have popped up where the ground seemed bare.
Along the end of the house a bank drops steeply to the drive below. Big rocks shore it up. The crevices bloom with a variety of perennials, but not much grows in the sandy soil at the top. One morning I decided to give it a good weeding, then plant ground cover there.
Another surprise! Buzzing filled the air as hundreds of swarming bees swirled ankle high above the ground.
No, they weren’t swarming…they seemed interested only in pursuing other bees going in and out of burrows in the ground. In some places, the holes were no more than two inches apart. The busy creatures ignored the big feet standing there in their midst, and they ignored the camera lens hovering just above them.
|Ground bees at work on their burrows (Click photos to enlarge)|
I hurried to my computer and found that the Northwest is home to several species of native ground bees. These include digger bees, alkali bees, bumble bees, leaf cutter bees and sweat bees (so called because they like to land on people and sip the moisture from their skin.) They all belong to the Hymenoptera order but are in different families.
Early spring is mating season for ground bees. They do not live in hives, as honey bees do, so there is no need for a queen. Each female digs her own nest in dry soil and gathers pollen and nectar for the young that will grow there. I watched several females start their burrows. As each kicked sand out, a miniature “hill” formed, with a slightly larger than bee-sized-hole in the center. Other bees returned to their own nests with abdomens yellow with loads of pollen. Meanwhile, the males hovered overhead, waiting their chance to grasp and mate with a female.
|A female at work on her burrow.|
The burrows go at least six inches into the earth, with vertical, horizontal, or slanting tunnels, depending on which species the bees belong to. The female lays an egg in her finished burrow, pushes in a lump of pollen and nectar for her baby to eat as it grows, then seals the hole. By next spring the larvae have developed into adults. Then they dig their way out to start the cycle over.
Ground bees can sting, but they are usually docile. However, I did see a few yellow jackets also burrowing in the same area. Yellow jackets can be cantankerous. Their stings are painful and they can sting repeatedly. Larger than ground bees, they are hairless and marked with a pattern of black and yellow stripes.
|How many burrow entrances can you count in this 6 inch patch of ground?|
Usually smaller than a half inch, the various ground bees are beneficial insects, indispensable as pollinators to farmers or gardeners. Pesticides should be used only as a last resort. To prevent them from nesting in your yard, try not to leave large, open patches of earth. Plant thicker grasses or use a mulch they will not find attractive to dig in.
Perhaps the easiest way to discourage them is to saturate the ground with water. They need drier earth to build stable burrows. I watered our colony of nesters and by the next day, only a few remained. They’d moved on to more favorable conditions. Of course, there’ll be a few larvae remaining in the ground, but by next year I’ll have a nice layer of mulch there to encourage the new generation to go elsewhere.