Valley Carpenter Bees: Big, Beautiful Thieves


This article was bittersweet to edit. As an Americorps member and Chad served with us for a set number of hours. He just completed his term of service and will no longer be working with us. Before he left he gave me a couple articles to edit and post. I hope you enjoy them. -Vincent


A female Valley Carpenter pollinates a passion flower. (By Mfield, Matthew Field,  - GFDL)

A female Valley Carpenter pollinates a passion flower. (By Mfield, Matthew Field,  - GFDL)

Imagine that you’re a honey bee (Apis spp.) that has left your hive in search of nectar. After a short flight, you have found it: a beautiful sage flower, full of sweet nectar. You zero in on your flower. A deep buzz comes from your right. You see a black object twice your size fly right by and land on the flower you had set your simple-heart-tube on. That object was your distant cousin, a female Valley Carpenter Bee (Xylocopa varipuncta) and your cousin is very important to the pollination of native plants. 

The Valley Carpenter Bee can be alarming when you first see it. They’re large as bees go, their whole genus is, roughly a third the length of a humming bird. Bulky, inch-long, metallic black females hum like conspiracy-theory black helicopters from flower to flower. The rarely-seen males are golden and fuzzy with gold-green eyes. The Valley Carpenters are the largest bees in California. Usually referred to as “black bumblebees”, they’re actually distant cousins to bumblebees just like honey bees. 

You might have encountered this bee before, nesting in or around your home. That’s because Valley Carpenters make their nest in wood prompting homeowner nightmares of hordes of bees drilling holes through weight-bearing timber. While this may be the case for some carpenter bees (I’m looking at you Xylocopa virginica), our Valley Carpenter Bee prefers the limbs of oak trees over human structures. Their nests are small, typically consisting of a long, double-ended passage and small side galleries for egg laying. They don’t form large hives. Typically nests are guarded and cared for by a mother bee and her unmated daughters, by several co-mated sister bees or a single mom. Brooding females don't make honey. Instead they make "bee bread", a mixture of pollen, nectar and bee saliva that aggregates into squishy balls. It's a far cry from brioche or sourdough but it provides everything a bee needs.

A male Valley Carpenter angles in toward a flower. (By Mfield, Matthew Field, GFDL 1.2)

A male Valley Carpenter angles in toward a flower. (By Mfield, Matthew FieldGFDL 1.2)

Males are solitary and do not participate in bringing up the brood, but they do occasionally claim and defend landmarks for mating purposes. Males will broadcast their availability to foraging females and wrestle other males out of the air in flower-rich territories. These wrestling matches look a little like two Golden Snitches fighting.  

The female Valley Carpenter Bee can frequently bee seen at the Our City Forest Community Nursery bouncing from flower to flower collecting some sweet sweet nectar. When observing this bee, I noticed that it was not approaching the flowers with deep tubular corollas (foxglove type flowers) from the flower’s opening. Instead she was approaching from the side of the flower. It’s nearly impossible for the Valley Carpenter Bee to reach nectar way down in the depths of a deep, narrow flower, so she turned to a life of “crime”. By piercing the side of the flower she is able to suck nectar out of the flower without going through the front door. This is a “crime” in that the flower relies on pollinators coming in the front to pick up and transfer pollen as they feed. Without that step, the mutualism between pollinator and pollination is lost

Don’t think that they break-and-enter every flower. Most flowers are accessible and don't need robbing by apiary criminal masterminds. In fact, the Valley Carpenter Bee is an important native pollinator, specifically for the passionflower. With their large size, they can collect far more pollen from a flower than smaller honey bees would be able to do. In agricultural settings they have been reported to be favorable pollinators over honey bees. There's actually research that supports using them as supplemental pollinators for many different agricultural products

The next time you see a big black bee, be not afraid. You're looking at a single mom or hard-working sister, collecting food to provide to her family. Should you be fortunate enough to find the aerial wrestling arenas of the golden, deadbeat Valley Carpenter Bee dads, sit, watch and try to get some pictures. It's the closest thing to Quidditch you can find in nature. 

 

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