Africanized honey bee with the corbicula full of pollen
Yummy, yummy! is the phrase that comes to our minds when remembering Winnie the Pooh eating all those pots of honey. Many of us may only have thought about honey bees for the first time when we were kids, thanks to that cute bear with the sweet tooth. Then we learned that we are not only indebted to honey bees for the wonderful miracle of honey, but also for the privilege of eating many of our delicious vegetables and fruits every day. Yes! Honey bees (Apis mellifera) are one of the most important pollinators of the crops that we the humans use all the time.
Some of us got so enthusiastic about this insect that we fell in love with it and became backyard beekeepers — we spend hours watching them buzzing around our sunflowers, pumpkins, lemons, sage and many other beautiful plants in our gardens.
What many of us do not know, however, is that there are other bees that can live and work in our gardens — and perform very important roles within them.
Leaf cutter bees are very interesting solitary bees. They belong to the family Megachilidae and they nest inside cavities and build their egg cells with pieces of leaves. They build multiple egg chambers per nest hole and in every one of them they deposit an egg with a little bit of pollen, nectar and saliva for the further development of the larvae (1, 2, 3).
You may be surprised and feel like you have never met one of these guys. Well think again and remember those times when you were walking around the garden and discovered some circular holes in your Roses’ leaves. You probably thought they were leaf cutting ants and were upset about them, but bee happy — there’s a good chance they were actually the female leaf cutting bees taking the material they use to lay their eggs.
Megachilidae are wonderful insects. Watching them carrying leaves and working to cover their nests is very beautiful, but they are also very important pollinators of crops like clover, alfalfa, fruits, some vegetables — such as onions and carrots — and wildflowers (5, 6, 7, 8).
Leaf cutting bee coming home
You probably don’t know it, but the pollination of alfalfa improved after the 1940s, when the leaf cutter bee from Asia (Megachile rotundata) entered the United States by accident. Suddenly, more alfalfa flowers got into seed and farmers began to reproduce these solitary bees and to create appropriate nesting boxes for them. This species is now present on all continents but Antarctica and keeps doing its job very efficiently, giving us the benefits of Alfalfa seeds (4, 9, 10).
How can you recognize leaf cutter bees? They are the size of a honey bee and for an untrained eye they look very similar, but here is the tip: while honey bees carry pollen in their corbicula (special structures in the tibia of the hind leg), leaf cutter bees carry the pollen that they collect on their scopa (elongated hairs on the abdomen). Also, many times you will see these bees carrying parts of leaves back to their nest and honey bees do not have this behavior.
Leaf cutter bee. Appreciate the long hairs on the abdomen for carrying pollen (scopa)
How can you attract these allies to your home garden?
- Take a wood block or a log (it doesn’t have to be too thick — 10 inches would be more than sufficient).
- With a drill, make some small holes
- If you want you can put a small roof onto the block to protect it from rain
- Hang the “leaf cutter bee house” in a sunny or partially sunny part of your garden
- Wait for the bees!
Read more on making a leaf cutter bee house here.
For those of you who are scared of bees, you’ll be glad to know that leaf cutter bees are not aggressive; they do not defend their nests like honey bees do. They only sting if they are manipulated and usually they bite before they sting. Furthermore, the sting is not as painful as those from honey bees.
Other friends of your garden will hopefully also inhabit some of the holes in the box.
Suddenly your small construction can become a very interesting community of amazing and very useful insects!
Bee and wasp
- “Leaf Cutter Bees”. 2012. WS Cranshaw, Colorado State University Extension
- “Leaf Cutter Bee", Megachile centuncularis. The Wildlife Trusts.
- “Leaf Cutter Bee, Genus Megachile” Aussie Bee Homepage.
- “The Domestication of the Leaf Cutter Bee”. 2008. Pollination Canada
- “The Leaf Cutter Bee”. 2014.
- “Leaf cutter bees-harmless, useful and often neglected pollinator”. 2011.
- “Leaf Cutting Bees”. 2005. David Serrano.
- “Leaf Cutting Bees, Megachile spp.” Beatriz Moisett
- “Alfalfa Leafcutting Bee, Megachile rotundata (Hymenoptera: Megachilidae). 2008. Mark S. Goettel. Encyclopedia of Entomology, pp 98-101.
- “The Alfalfa Leafcutting Bee, Megachile rotundata: The World’s Most Intensively Managed Solitary Bee”. 2011. Theresa L. Pitts-Singer and James H. Cane. Annu. Rev. Entomol. 56: 221 – 37.