The narrowleafed milkweed, Asclepias fascicularis, beckons monarch butterflies (the host plant), aphids, praying mantids and assorted other insects, but once in a while, you'll see a leafcutter bee. Both the plant and the bee are natives.
This male bee (below) spent the afternoon patrolling for females, but it rested in between.
It's a dangerous place to rest when there's a predator (praying mantis) around, but all ended well.
Leafcutter bees, spp., so named because the females cut leaves and petals (perfectly round holes!) to line their nests, are smaller than honey bees--and much faster. They're easily recognizable by the black-white bands on their abdomen.
The females do all the work. They gather pollen and nectar, make the nests from the leaf and petal fragments, and lay eggs. They seal the egg chambers with the leaves or flower petals.
The male's job is to reproduce. And sometimes, you'll see one sunning itself on a milkweed leaf.
Of the 4000 bee species known in the United States, about 1600 reside in California. The leafcutter bee is just one of them. The family, Megachilidae, includes these leafcutting bees, Megachile angelarum, M. fidelis and M. montivaga; the alfalfa leafcutting bee, M. rotundata; the Mason bee, Osmia coloradensis; and the blue orchard bee (BOB), Osmia lignaria propinqua.
For more information on California's bees, read California Bees and Blooms: A Guide for Gardeners and Naturalists (Heyday), the work of UC-affiliated scientists,/span>
Day 5 of National Pollinator Week: Meet the leafcutter bee, family Megachilidae.
It's a native pollinator, a solitary bee, and about the size of a honey bee.
Its coloration--the black-and-white banded abdomen--makes it easily recognizable.
As the name suggestions, they (the females) cut circular holes in leaves to line their nests for brood-rearing. Rosarians who enter their roses in competition aren't fond of them because of the "imperfections" in the leaves. A hole in one--or holes in many--aren't going to give them a whole lot of blue ribbons.
But having leafcutter bees in your garden is a joy. They're good pollinators and gentle bees. Leafcutter bees carry pollen on the underside of their abdomen, not on their hind legs like honey bees, do. Agriculturists manage the alfalfa leafcutter bee (Megachile rotundata) for crop pollination.
Leafcutter bees nest in natural cavities, mostly holes in soft wood or in hollow, pithy plant stems. You can also create bee condos or housing for them, drilling specific-sized holes in a block of wood.
We saw this little male Megachile foraging on Verbena. He paused for a few minutes and then took flight. Things to do and places to go...
If you want to attract insects to your garden, plant an artichoke and let it flower.
You'll get honey bees, syrphid flies, butterflies, carpenter bees and leafcutter bees. (And well, a few predators, such as spiders and wasps.)
Today we saw leafcutter bees (Megachile spp.) tumbling in the purple strands, looking so much like residents of a gated community. A purple gated community.
These native bees, so named because they cut fragments from leaves and bring them back to line their nests, are excellent pollinators. They nest in our bee condo, just inches away from the artichoke plants.
Then we saw a male cuckoo leafcutting bee (below), genus Coelioxys, as identified by native pollinator specialist Robbin Thorp, emeritus professor of entomology at UC Davis. "The females hide their eggs between the leaves in Megachile nests and their larvae kill the host egg or larva and complete their development on the pollen provided by the host female," he said.
With Megachile, if you provide a bee condo (a wood block drilled with holes), you may see these tiny insects provisioning their nests. (See the list of resources provided by Thorp, on the Harry H. Laidlaw Jr. Honey Bee Research Facility website.
All in all, leafcutter bees are a star attraction for National Pollinator Week, which began Monday, June 18 and continues through Sunday, June 24.
All winter long my bee condo housed 16 tenants...and one earwig.
And quite comfortably, too, thank you.
It all began last fall when the leafcutting bees laid their eggs, provisioned each nest with a nectar/pollen ball, and plugged it with leaves.
Just about every morning, I did a bed check. Yes, 16 tenants and one earwig. (In actuality, there were probably more of those nasty little earwigs, but each time I checked, I found only one. But lots of frass!)
Bee condos are really just wood blocks drilled with tiny holes for native bee nests.
In late April and early May, the tenants began to stir. As of yesterday, 13 holes had popped open. Ah, emergence! The nocturnal earwig? Nowhere in sight.
You, too, can rear leafcutting bees (Megachile spp.) in your yard. All you need is the housing, which you can buy at most beekeeping supply stores or online. You can also go online and buy the plans to build them.
Senior conservation associate Matthew Shepherd of The Xerces Society for Invertebrate Conservation, in his fact sheet about native bee nesting sites, wrote: "There are 4,000 species of native bees in North America. Together they form the most important group of pollinators. Like all wildlife they are affected by changes in our landscapes, especially the loss of nesting sites. Bees make nests in which they create and provision brood cells for their offspring. In many modern landscapes, a desire for neatness has usually resulted in the removal of bare ground, dead trees, and untidy corners of rough grass—all important nesting sites for bees."
Native pollinator specialist Robbin Thorp, emeritus professor of entomology at the University of California, Davis, has provided a list of resources for native bee nesting requirements. It's available free on the Harry H. Laidlaw Jr. Honey Bee Research Facility website.
And, the Xerces Society recently published a Pollinator Conservation Handbook where you can find more information about our pollinators.
Just don't expect all your tenants to be pollinators, and all your pollinators to be tenants.
Sometimes you get lucky.
While watching floral visitors foraging last week in our rock purslane (Calandrinia grandiflora), we noticed a tiny black bee, something we'd never seen before.
Native pollinator specialist Robbin Thorp, emeritus professor of entomology at the UC Davis Department of Entomology, identified it as a female leafcutting bee, Megachile gemula, "which has an all-black form."
It's a rather uncommon bee, but a distinctive bee, said Thorp, who is one of the instructors of The Bee Course, offered every year in the Southwestern Research Station, Portal, Ariz., for conservation biologists, pollination ecologists and other biologists who want to gain greater knowledge of the systematics and biology of bees. Participants come worldwide to learn about bees.
Megachile gemula is native to the United States. The females snip round holes in leaves and line their nests with the material. From egg to larva to pupa, a new generation emerges from the sealed nest.
Meanwhile, if you want to go on a walking tour with Thorp, mark your calendar for Friday, June 22. Thorp will lead a Tahoe National Forest Service tour of native plants and pollinators in the Loney Meadow, near Nevada City, Nevada County. The tour, free and open to the public, will take place from 10 a.m. to approximately 2 p.m.
The walk is provided as part of the Forest Service Pacific Southwest Region’s 2012 Pollinator Special Emphasis Area "which has been developed to call attention to the importance of butterflies and native bees in providing important services for food production and ecosystem health," said Kathy Van Zuuk, Yuba River Ranger District botanist and forest level non-native invasive plant coordinator.
And what bees might tour participants encounter? Probably bumble bees, mining bees, digger bees, leafcutting bees, mason bees and cuckoo bees, Thorp said. Other floral-visitors are expected to include flies, butterflies, and beetles, he said. Van Zuuk and fellow botanist Karen Wiese will identify the native plants.
Those interested should meet at 10 a.m. at the Sierra Discovery Trail parking lot located off Highway 20 to carpool to Loney Meadow (where parking is limited). Participants of all ages should bring water, snacks, insect repellent, sunscreen and wear suitable footwear. (No dogs, please.)
Further information is available by contacting Van Zuuk at (530) 478-6243 or emailing her at email@example.com.