Honey bees, yes! Bumble bees, yes! Carpenter bees, uhh, not so much.
Ever seen carpenter bees drilling holes in dead limbs or untreated fence posts to build their nests? No? Well, you've probably seen them in their "robber role," piercing a hole in the corolla of a flower and robbing the nectar, bypassing pollination.
"Beneficial insects or pests?" we asked native pollinator specialist Robbin Thorp, distinguished emeritus of entomology at the University of California, Davis.
"Carpenter bees are controversial and their status as pests or beneficial insects is complicated," Thorp noted. "Some people consider only the negative effects of carpenter bee behaviors--tunneling in wood structures we create or nectar-robbing from some long-tubed flowers--deeming them pests and seeking ways to control them.
"But carpenter bees are important pollinators in native plant communities, and even beneficial as pollinators of some crop plants such as passion fruit, blueberries, melons, hybrid cotton and they are effective buzz pollinators of tomatoes and egg plant," he said. "Even effects of their nectar robbing are not entirely negative. They may actually enhance out-crossing by forcing legitimate pollinators to visit more flowers thus increasing out-crossing. In some cases, they may actually pollinate flowers while nectar-robbing from them."
"Carpenter bee tunneling into wood is an initial step in breaking down dead limbs and logs as part of the recycling process in natural communities. It is when they burrow into untreated wood used in our constructions that they are considered pests."
Thorp said that "any damage caused by them should be weighed against their positive contributions in trying to determine whether to attempt to control them or not."
Bottom line: we consider carpenter bees beneficial.
California has three species of carpenter bees.
- The biggest is the Valley carpenter bee, Xylocopa varipuncta. It's about an inch long. The female is solid black, while the male, commonly known as "the teddy bear bee," is a green-eyed blond. Why teddy bear? It's fuzzy and does not sting--or as Thorp says "Boy bees don't sting."
- The second largest is the California carpenter bee or Western carpenter bee, Xylocopa californica, often found in the mountain foothill areas of northern and southern California. It's known for its distinctive distinctive bluish metallic reflections on the body, Thorp says. The females have dark smoky brown wings.
- The smallest is the foothill or mountain carpenter bee, Xylocopa tabaniformis orpifex. The females are black with light smoky-colored wings. The male has bright yellow marks on the lower part of its face and some yellow hairs on the top front of its thorax.
Check out the images and descriptions of carpenter bees on BugGuide.net).
Want to hear more about California's bees, which total some 1600 species? Thorp will be giving a two-hour presentation, "Bee Aware Bee Cause," on Saturday, Jan. 7 starting at 1:30 at the Rush Ranch Nature Center, 3521 Grizzly Island Road, Suisun. The site is located off Highway 12, two miles south of Suisun City. The event, free and open to the public, is sponsored by the Rush Ranch Educational Council, in partnership with Solano Land Trust, owner of Rush Ranch.
Thorp, who holds a doctorate in entomology from UC Berkeley, taught entomology at UC Davis from 1964 to 1994. Although emeritus since 1994, he continues his research, writings, bee identification, public outreach and other "bee-involved" activities from his headquarters in the Harry H. Laidlaw Jr. Honey Bee Research Facility at UC Davis.
Thorp co-authored the UC California book, California Bees and Blooms: A Guide for Gardeners and Naturalists (Heyday) and Bumble Bees of North America: An Identification Guide (Princeton University Press). He annually teaches at The Bee Course (American Museum of Natural History), at the Southwestern Research Station, Portal, Ariz. The two-week course is offered for conservation biologists, pollination ecologists and other biologists who want to gain greater knowledge of the systematics and biology of bees.
If you have a patch of salvia (sage) growing in your yard, watch for the nectar robbers.
Carpenter bees are among the insects that engage in nectar robbing. They drill a hole in the corolla of the flower, circumventing the usual plant-pollinator relationship. In other words, they're “cheating” pollination by "stealing" the nectar. Scientists call this "robbing the nectar."
The most prevalent nectar robbers in our yard are the mountain carpenter bees, Xylocopa tabaniformis orpifex. They're better at drilling holes than the Texas oilmen.
If you watch closely, you may see a honey bee following the carpenter bee around. She's taking the easy way out, finding the hole pierced by the carpenter bee and then gathering nectar to take back to her colony.
If a flower could communicate, it would probably say something like "Hey, you're doing an end run to get my nectar. Please don't use the side entrance--I have a front door."
Look at the Xylocopa on the Xanthorrhoeaceae.
If that sounds like a mouthful, think of the mountain or foothill carpenter bees, Xylocopa tabaniformis orpifex, on bulbine from the genus Bulbine in the family Xanthorrhoeaceae.
Carpenter bees and honey bees are among bees attracted to the yellowish-orange flower with bearded stamens. A native of South Africa, it's also known as yellow bulbine, snake flower and cat's tail.
The carpenter bee below is a male nectaring on Bulbine frutescens.
Bulbine is blooming now in the Häagen-Dazs Honey Bee Haven, a half-acre bee friendly garden planted in 2009 by the Harry H. Laidlaw Jr. Honey Bee Research Facility on Bee Biology Road, UC Davis.
The garden, owned and operated by the UC Davis Department of Entomology and Nematology, is open from dawn to dusk for self-guided tours. Admission is free. The art that graces the garden is the work of the UC Davis Art/Science Fusion Program.
The garden's mission: to provide a year-around food source for the bees at the Laidlaw facility and other pollinators; to draw attention to the plight of the bees; and to give visitors an idea of what they can plant in their own gardens.
We all take short cuts--short cuts around the campus, to the beach, to a favorite restaurant...
Honey bees take short cuts, too.
We've often watched assorted bumble bees and carpenter bees drill a hole in a long-tubed flower to rob the nectar.
And we've watched honey bees benefitting from this behavior.
Today we observed a carpenter bee, Xylocopa tabaniformis orpifex, engaging in nectar robbing in salvia at the UC Davis Arboretum. Nectar robbing occurs when a bee or other animal circumvents the usual plant-pollinator relationship and "cheats" by entering a flower from the outside to steal nectar, thus avoiding pollination or contact with the anthers.
There's excellent information on bumble bees, their habitat needs, their behavior, and identifying characteristics in a free, downloadable PDF from the Xerces Society for Invertebrate Conservation: "Conserving Bumble Bees: Guidelines for Creating and Managing Habitat for America's Declining Pollinators."
The PDF mentions that "short-tongued bumble bees will engage in 'nectar robbing' from flowers with a long corolla tube by biting holes at the base of the corolla and drinking the nectar from the outside of the flower." The bee grabs the reward but doesn't contribute to "the plant's pollination needs."
Meet a carpenter bee.
This one (below) is a male carpenter bee, Xylocopa tabaniformis orpifex, as identified by native pollinator specialist Robbin Thorp, emeritus professor of entomology at the University of California, Davis.
It's also called a "mountain" or "foothill" carpenter bee.
When it slits the corolla of the flower--in this case, salvia--and bypasses the pollination process--this is called "nectar robbing."
The mountain/foothill carpenter bee is the smallest of the three species of carpenter bees in California, Thorp says. The other two are the Valley carpenter bee, Xylocopa varipuncta, the largest, and the California carpenter bee, Xylocopa californica, the second largest.
The male of the Valley carpenter bee is a green-eyed blond and often referred to as a "teddy bear." The female of that species is solid black. And huge!
The California carpenter bee or Xylocopa californica is known for its distinctive distinctive bluish metallic reflections on the body, Thorp says. The females have dark smokey brown wings.
The one photographed below, Xylocopa tabaniformis orpifex, is common in the center of the Central Valley, "probably due primarily to increased nest sites such as redwood arbors and fences," Thorp says. Although considered a pollinator instead of a pest, "it can be a pest when it gets into untreated redwood used for water tanks or structural timbers," Thorp points out. "The females are black with light smokey-colored wings. The male has bright yellow marks on the lower part of its face and some yellow hairs on the top front of its thorax."
You can see the yellow hair on the thorax.
And how big is the smallest of the three carpenter bees? "Much larger than a honey bee, but about half the size of the other two carpenter bees," Thorp says.