Leafcutter Bees

Have you ever noticed holes in your plant leaves and assumed they were the work of a hungry caterpillar or beetle? Perfectly rounded  or oval holes on the edges of a leaf are usually the sign of a nearby nesting leafcutter bee (Megachile spp):

Female leafcutter bee cutting a small piece of leaf to wrap around the brood cells in her nest in nearby trees, logs or old plant stems. Leafcutter bees are one of a huge diversity of native American bees that you can easily attract to your wildlife garden. Photo by Bernhard Plank (Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.)

Holes in leaves cut by native leafcutter bee

Unlike the ragged edges of Japanese beetle leaf holes, the neatly outlined holes on the edge of these redbud leaves are the work of native leafcutter bees. Nectar plants will attract these bees, but to survive from year to year, leafcutter bees need overwintering nest sites.

Unlike butterfly and moth caterpillars, or herbivorous beetles such as the dreaded Japanese beetles, leafcutter bees don’t eat leaves, but cut off small pieces of leaf to use in building their nests. Leafcutter bees are among a large number of bee species known as “solitary” bees because they don’t live in social hives, like honey and bumble bees. This is important, because bees without a nest to protect are unlikely to sting you unless you physically threaten them…

Female leafcutters lay their eggs inside hollow plant stems or in existing holes or beetle tunnels in trees, and use leaf cuttings from nearby plants to build sturdy walls around the eggs to keep them safe and dry in their nest right through the winter. Both males and females visit flowers for nectar to fuel their flight, but females also collect pollen and nectar, which they to use to stock their nests with a food supply for the young bees after they hatch. Hatchlings feed on these “pollen balls” til they emerge from the nest the following year.

If your property has brushy areas with lots of old plants, or a few old trees with natural cavities, you could well already have resident leafcutter bee populations. But to really increase population survival from year to year (or if you live in an area where a more manicured look is required), you can provide nesting sites by hanging a “bee box” which many native bees and other beneficial insects will readily use. This can be a bundle of dried stems of various widths or even just a piece of untreated wood drilled with holes of varying diameters. Leafcutter bees may even use a garden hose for nesting…not a wise choice unless the gardener is willing to sacrifice their hose til the hatchlings emerge the following year…

 

A few of these stems have been filled with bee nest cells and sealed off for the winter

Create a beneficial insect nesting box by drilling holes of varying sizes into untreated wood. Don't drill all the way through the wood, some wood nesters prefer one end of their nest tunnels to be blocked..

Leafcutter bees seem to have local preferences for the plants they like to use for nesting. In my area of MA they seem to prefer eastern redbud (Cercis canadensis) leaves, which make a smooth and soft nest for baby bees. If you see leafcutter holes on your plant leaves, please share with us the species! It’s always interesting to hear about regional preferences, and discover the plants in our backyards that provide the widest range of resources for wildlife…

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Comments

  1. dcs says

    In my yard they go straight for the Hydrangea petiolaris. Interesting that the leaves on it are similar in shape to Cercis.

  2. Carole says

    Thank you for showing what the evidence looks like, I’ll be on the lookout. We had one attempting to build in the rubber trim around our door on the inside of a house we were having built. The leaves didn’t quite fit and the rejects littered the floor.

  3. says

    Kathy, according to my Xerces Society book “Attracting Native Pollinators” (highly recommended BTW), there are native leafcutter bees in California. The book mentions that there is a non-native imported leafcutter bee (Megachile apicalis) which competes with the native species for nesting sites, so clearly there is some concern for the native species. The book also men tions that there are 140 species of leafcutter bee native to the US…
    Ellen Sousa recently posted..The Year I Shall Win the Pachysandra War

  4. says

    WOW! You just solved a mystery for me that occurred this week. I was out and spotted a bee with a “green bottom” flying through the air. It looked odd so I followed it and took a few photos. While looking at the photos, nothing seemed unusual….well, now I know why. It must be a leafcutter bee that was carrying the leaf to nest, but in the photo, since it landed on a plant, it wasn’t obvious.

    Thanks for the great information, Ellen. I still learn so much on a weekly basis here!
    Loret recently posted..Pond Prank

  5. says

    The leafcutter bees here seem to prefer rose leaves. I’m not sure of the variety of a “surprise” rose on my property, but they also use my swamp rose, Rosa palustris. When I wrote a post on leafcutter bees, some of my readers also reported that the bees used their rose leaves. I have the same bee house! Although I fear the birds ate some of the new plugs this year. I have to make a new one.

  6. Lantana104 says

    This is just amazing. We live in Central Texas just north of San Antonio and have had them take pieces of our native redbuds. I could never figure out what was cutting those perfectly circular little pieces. We have a mostly native plant yard, similar to habitats described in your article. Mystery solved! And, now you know that they are as far south as Texas! Thanks so much.

  7. Gillian says

    Hi I have just noticed these perfectly cut semi circles on my rose bush. I am not sure what the rose is as I was given a cutting from my Aunt in Ireland.
    We have recently moved to our house and have inherited a bee house too!, which is sited very close by. Thanks for the information, just one question will it harm my roses? Thanks again, Gill

    • says

      Gill, they won’t harm the roses, their damage is minor compared to what pests such as Japanese Beetles do to roses! They are not eating the leaves, just using them to construct their nest cells…

  8. audrey says

    I have a leaf cutter who is making her nest in the underside of a hanging planter. Very cool watching her come and go with the pieces of leaves! First time I’ve seen one!!

  9. Chris says

    I live in the Austin tx area. I was inspecting my Tx redbud tree for caterpillars because huge circles were missing out of the leaves, and I was perplexed as to what was doing it. At that moment, a big bee landed on the tree and literally cut a circle out of a leave in no time and flew off with it. I learn something new everyday. I’m going to find a natural deterant spray. The trees are new and look bare now.

    • Judith says

      I noticed holes in an Eastern redbud tree in the Bronx, New York, and a few on a rosebush.One day saw an insect, which I first thought was a wasp, making holes on redbud leaves. When I looked it up it was a leaf-cutter bee. The tree is quite large so there is no harm in having some leaves chewed. Ellen’s pictures are terrific!

Trackbacks

  1. [...] 5. Leaf Cutter Bees, by Ellen Sousa. “Unlike butterfly and moth caterpillars, or herbivorous beetles such as the dreaded Japanese beetles, leafcutter bees don’t eat leaves, but cut off small pieces of leaf to use in building their nests. Leafcutter bees are among a large number of bee species known as “solitary” bees because they don’t live in social hives, like honey and bumble bees. This is important, because bees without a nest to protect are unlikely to sting you unless you physically threaten them…” [...]

  2. […] tightly on the bottom with a single egg poking out the top.  Obviously we were dealing with some sort of bee.  Research showed that we had discovered the nest of a leaf-cutter bee, and that the pollen is […]

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