The leafcutter bee: nature’s hole punch

Leafcutter
A leafcutter bee in western Washington. © Rusty Burlew

The bee in the photo is a leafcutter or leafcutting bee in the family Megachilidae. This is the same family that contains the mason bees, and like mason bees, female leafcutters carry pollen on their abdomens rather than on their legs.

A telltale sign of a leafcutter is a slight arch in her back, which you can see in the photo above. Most bees seem to bend in the other direction, and whenever I see a leafcutter she reminds me of a little gymnast saluting the judges before her performance.

Also like mason bees, leafcutters commonly live in hollow reeds or abandoned beetle holes, and they are perfectly happy to reside in man-made bee blocks. The one in the photo is most probably an alfalfa leafcutting bee, Megachile rotundata, an introduced species that was brought to North America to pollinate alfalfa—a crop in which honey bees do a poor job.

Not surprisingly, leafcutters cut leaves. The female cuts small round disks from leaves and petals and uses these to line her nest. If you look at a bee block, holes containing mason bees will be sealed off with mud or gravel, but the holes filled with leafcutters will be finished with green disks or sometimes with colorful petal parts.

Gardeners are often mortified to see the leaves of their prize roses shot though with holes, but the bees do no permanent harm to the plant. Although the leaves look less than perfect, their presence lets you know you have a host of excellent pollinators working close by.

Alfalfa fields are commonly populated with leafcutter domiciles, in which thousands of nests are constructed. Each hole is the nest of one solitary female. Although strictly solitary, they don’t mind living in large communities.

The bees are extremely gentle. Last summer I stood in some of these domiciles, taking photos at the height of alfalfa pollination in eastern Washington. The air was thick with bees, the domiciles smelled richly of alfalfa, and the sound of wings was deafening. But I wore no protective clothing and I was never warned, chased, or stung—they are just too busy to be bothered with anything but raising their young.

Unfortunately, these vast leafcutter bee communities promote disease, especially chalkbrood. Like honey bees, new bees have to be raised elsewhere and shipped in to replace those that die of leafcutter diseases. Those that live separately and away from agricultural areas are less likely to be infected.

If you want to attract leafcutters to your garden, you can provide wood blocks or reeds with holes that are about 1/4-inch in diameter—slightly smaller than those used for mason bees. If you use a variety of hole sizes in your pollinator housing, you can attract a mixture of different species which are less likely to pass diseases among themselves.

Rusty
HoneyBeeSuite

Leafcutter-domicile
A leafcutter domicile in an alfalfa field. © Rusty Burlew
Inside a leafcutter domicile.
A leafcutter domicile contains hundreds of thousands of holes, each about 1/4-inch in diameter. © Rusty Burlew
Leafcutter-at-home
An alfalfa leafcutter seals up her nest with a freshly cut leaf. © Rusty Burlew

Comments

Trent
Reply

I grew up in the Columbia Basin, and while I never worked on farms that grew alfalfa seed, I certainly had friends whose fathers farmed and had leafcutter bee houses in their alfalfa fields.

Occasionally I would help out with clearing the boards of the worms that would eat the larvae, and the leafcutter bees we worked with didn’t sting, or so I was told, but they did bite if one got curious enough to crawl down your shirt.

Rusty
Reply

It always amazes me how many bees will bite, even honey bees.

HB (@Hello_Kitty_)
Reply

I hope to have luck with the leaf cutters, as I know they are around. Here is a “video” (three images) I captured of a leaf cutter on a young wisteria. http://youtu.be/NnuKlt3Sj9w The instant the leaf piece was free, she took off, and I couldn’t find where she went. This year I am trying different sized tubes and hope the leaf cutters pick some to nest in.

Rusty
Reply

They are so cool because they never drop the leaf. They kind of sit on the part they are cutting out. You think it will be a disaster, but like you say, they take off at exactly the right moment.

Glen Buschmann
Reply

Thanks Rusty leafcutters are definitely the bee I delight in, one of my current obsessions. I want to know more and more about them, keep making what seems like little inroads – a nest here a sighting here, a few leaves cut out there, a bee flying in with cut-outs while sitting on the front porch. Then there is this delightful article: it is from a bunch of years old but the quality of research carried out by a 14 year old on leafcutters still impresses me, reminds me that small things do matter.

http://www.amnh.org/learn-teach/young-naturalist-awards/winning-essays2/2008-winning-essays/nesting-preferences-of-the-alfalfa-leaf-cutting-bee

Glen B

John
Reply

How deep are the holes?

Thanks,
John

Rusty
Reply

Four to six inches works well.

Debbie
Reply

I’m so excited because mine holds reeds that are all different sizes. I do hope to see some leafcutter bees in my little apartment dwelling. Thank you so much Rusty for informing us on other bees beside honey bees.

I live in the city and was wanting to start a hive of honey bees. I always have lots of bees & critters in my garden. All of my neighbors have small children & I would be devastated if one of them got stung. You have opened my eyes to an alternative to helping save not only Honey Bees but all pollinators.

I am an artist and love nature. I will do my part as well as photograph & paint bees & other pollinators. Thanks for opening my eyes to other alternatives besides beekeeping. Though I love them & love walking amongst them in my yard, it is not for me at this time. I now have other ways of doing my part. Thank God we aren’t all made the same…just like the bees.

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