Balkan Ecology Project : May 2015

Continuing the series of posts on Garden Allies, this post will be looking at ground bees, a not so well known group of insects that are important crop pollinators.

What prompted me to write this post was the observation of a number of mini volcano shaped earth mounds on the lawn this Spring.

Ground Bee Nest - Yet to identify the inhabitant

We set up a video over one of the holes hoping to catch a view of the comings and goings of the inhabitants and discovered a very small bee at work. My son Archie put together this short film of the bee, cheers Arch.

What Are Ground Bees?

Ground-nesting bees are largely solitary bees i.e, do not live in colonies like honey bees, and include species of digger bees (family Anthoporidae), sweat bees (family Halictidae), and mining bees (family Andrenidae). Solitary bees are especially important as pollinators as many feral social bees are in danger due to dwindling numbers and parasites.

Generally females excavate a nest in dry soil, and mound the loose soil around the nest entrance. She provisions the nest with pollen and nectar for her offspring. To get an idea of how much pollen these bees can collect see on the above video her pollen laden legs on return from a 10 minute forage.

Each female digs and provisions her own burrow. However, it's not unusual to find dozens of ground bee nests in one area if conditions are suitable for nesting. Males may fly over the burrows, patrolling for potential mates.

Ground bees are not aggressive. Females will, however,sting in defense if threatened. Males of some species may behave aggressively around nesting areas, but they lack a sting.

Bumblebees also nest in underground burrows. The Bumblebee nest is typically bigger and they live in social colonies so if you see multiple bees entering or exiting the nest you can be sure they are not the harmless ground bees. Social bees like bumblebees will aggressively defend their nests.

Bumblebee - Bombus spp.

Some wasps are also ground nesters, for more information See Garden Allies - Wasp.

What can you do to attract bees?

In the ecological garden we often apply thick layers of mulch on bare soil, however the bees cannot nest in this. Leaving some areas of bare soil around the garden will provide nesting habitat for the solitary bees. In certain places in our garden we have 1m wide bare earth pathways and the edges of these paths do not get frequently trodden make good nesting sites. Plant diversity in all layers of your garden will provide a variety of foods and at different times of the year. Species-rich meadows are particularly beneficial, even if on a small scale (see plant list below) .

For the bumblebees that also nest in the ground, you can provide areas of rough grass, preferably by a hedge, such as those sites favoured by nesting mice or voles. You may wonder how this is connected with bees? Queen bumblebees are known to like inheriting and nesting in old mouse and vole nests.

Edible and useful plants that also attract bees

All of the plant below are available from our Bionursery and are edible and useful plants for humans as well as many other organisms. Click on the links for photos and info. I have also included a broader list of plants that are known to be good bee plants, these may or may not be edible.