Updated: 25th February 2021
The leafcutter bee belongs to the Megachile family of bees, and is another useful friend to gardeners, providing a valuable and efficient pollination service for plants.
Have you ever noticed little segments cut away from roses, lilac or other shrubs?
If it’s leafcutter bees, there will be a neat crescent or almost circular shaped hole in the leaf. If you should find this, do not worry, usually it will not cause lasting harm to your plants. (Remember, plants survive pruning and dead–heading!).
So, please don't spray your plants with pesticides.
Here is a video taken by Alec Short, showing a leafcutter bee cutting a piece of leaf, then flying off with it (Alec has kindly agreed to allow me to use the video):
Leafcutters always cut away segments of leaf in a very neat, circular fashion. Jagged cuts or rips in leaves are nothing to do with leafcutter bees.
Leafcutter bees are increasingly recognised for their farm crop pollination service. In fact, the US Agricultural Research Service state that 1 alfalfa leafcutter bee can do the job of 20 honey bees! Surprisingly, in research, they discovered that about 150 of these little bees working in greenhouses (or similar) can provide the pollination service of 3,000 honey bees (1).
The newly emerged females begin constructing nests after they emerge in spring. In each nest cell they lay a single egg, and supply it with pollen upon which the larva can feed once it hatches.
The larvae pupate and develop inside these cells. They will over-winter in their cells as mature larvae, and emerge as adults the following spring or early summer.
Like mason bees, leafcutters are ‘cavity nesting’. This means they like to make their nests in ready-made cavities, twigs or in soft rotting wood that can be ‘excavated’.
Once a suitable spot has been
found, they will begin collecting segments of leaf for their nests.
The bees construct their nest cells by using pieces of leaf, to line the cavity, and by overlapping segments of leaf to make a cylindrical tube shape that looks a little like a cigar.
Each cell is sealed up at the end with a further segment of leaf. Nests are small: generally around 4 to 8 inches long.
Some species line their egg cells with petals
instead of leaves. The silvery leafcutter bee, for example, may use the flower petals of bird's foot trefoil.
Below is a small amount of video I managed to capture, of a leafcutter bee female carrying a segment of leaf back to her nest.
It's a very short clip, because I had to lean over some large pots in order to film. This made it difficult for me to sustain filming for a long period of time, so that most of my video clips were very shaky and not at all very good. Anyway, the segment of leaf is carried below the body of the bee, and transported to the nest site - in this case, some hollow canes.
Below is another species of Leafcutter bee: the Carpenter-mimic Leafcutter bee, Megachile xylocopoides. The video was kindly supplied by Tracy L. Elfers of Florida. It has used a collection of envelopes and letters as a 'cavity'. Instead of relying on a pre-constructed tube or tunnel (as might be provided by a hollow twig or cane), it has created its own 'tube' using segments of leaf, with the letters and envelopes providing a kind of 'cavity' that support and shelter the construction. The whole process of the bee arriving with a piece of leaf and depositing it into her cells takes about 3 minutes.
I received an interesting email from a Lesley Urquhart,:
My initial thoughts was that this must be the work of a predator, although it seemed unusual, so on Twitter, I asked an expert from the Natural History Museum in London (please note, I am no longer active on Twitter). This was the response:
In case you have difficulty reading the tweet from the Natural History Museum in the image, it states:
"Remains of leafcutter bee (Megachile) cells. Sometimes female leafcutter bees clear existing nest sites to make space for their own cells."
I was then told by Steven Falk (author) that it was a form of 'usurption'. I was aware that usurption can happen in bumble bees, (true bumble bee queens may fight over nest sites - this is different from cuckoo behaviour) but had no idea it might be seen in leafcutter bees. Well, you learn something new every day!
On first sighting, many species of solitary bee can easily be mistaken for honey bees or even hoverflies. So how can you tell the difference between them, if the leafcutter is not engaged in the activity of cutting leaves or building its nest, but instead, is foraging on flowers?
One give away lies in their methods for collecting pollen. Many other solitary bee species, along with worker honey bees (and indeed bumble bees), collect pollen on their hind legs, then transport it back to the hive or nest.
bees however, collect pollen on hairs on the underside of their abdomens - their 'pollen brush'. When the bee is carrying pollen, it is often quite visible, sometimes as a whitish cream, pale yellow colour, pale orange or bright orange colour, but when covered in pollen the actual colour of the brush itself may not be visible.
At times when foraging, the pollen brush pokes in the air, and is more easily visible.
Lots of people would like to be able to watch leafcutter bees in action.
They are fascinating to watch, and in a way, amusing: to see a little bee carrying a piece of leaf as large as itself, or even larger, is wonderful to see!
Leafcutter bees are rather docile, not aggressive.
possible to encourage them into your garden by providing bundles of
hollow canes, or a log of wood drilled with holes up to 1cm in
diameter (don’t use varnish, preservatives or any other chemicals).
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