Valley Carpenter Bee

It may be hard to believe but the 1/2" diameter holes, that have been bored in the trunk of our bottlebrush tree and in a dead apricot stump, were made by valley carpenter bees (Xylocopa varipuncta).

These large bees are not bumble bees, though they do make a loud buzzing sound. And while they are large in size, only the females have a stinger and they are very reluctant to sting. These are bees you should try to attract to your yard. 

male valley carpenter bee

Carpenter bees are native insects and important pollinators. They are more efficient at pollinating than European honey bees, but these native bees are dependent on some of their food coming from native nectar-bearing plants. Many of our sages evolved with these bees.

female valley carpenter bee

There are several species of carpenter bees in the Los Angeles area, but the valley carpenter bee is the largest–typically an inch long. Females are shiny black while the males are a golden yellow.  These large bees are solitary, they do not form a hive.

 The female valley carpenter bee drills into wood, gnawing with powerful jaws. I've watched them and they seem to gradually rotate so that the hole comes out perfectly round. This tunnel into the wood is where she lays her eggs. She places pollen and nectar at the end of the tunnel and lays an egg. Then she closes off the rear section with a pulp wall. In this manner she creates 5-6 small chambers for larva to develop in the tubular nest. When they mature the young bees gnaw their way out of the tunnel and into the world.

female valley carpenter bee arriving at nest tunnel

Females also tunnel into wood to create a hibernation chamber to sleep away the winter. New males will be born in the spring. 

We regularly see several females and an occasional golden-colored male in our garden. They usually follow a regular schedule, visiting specific parts of the yard at the same time each day.

This spring for the first time, I saw two males at the same time. The males were wrestling mid-air struggling over territory. In the end, one of them went off to find a different location.

I love seeing these big bees in the garden. They are gatherers of abundance, yet they are also vital philanthropists spreading pollen as the foundation of tomorrow's garden. 

Plants for native bees:
small bracted dayflower (Commelina erecta)
Fremontia
giant coreopsis (Coreopsis gigantea)
coffee berry 
 

Building a Native Bee Box

I've been wanting to do this for over a year, build a nesting box for native bees and other insects. My friend Doug Welch from A Gardener's Notebook had sent me various plans and ideas. I had a wooden wine box with a sliding lid and it seemed perfect.


Finding the western bumble bee nest in one of my bird houses finally prompted me to just do it.

I drilled holes of 3/8", 1/2" and 5/8" in the lid. Different bee species prefer different size holes. Then I filled the box with hay and dog hair. These were the kinds of fibers in the bird house that the bumble bees had liked.

I mounted two hooks on the back of the box so I could hang it on the fence at the side of the garden. 

In this location we can see any activity at the nest box, it is near the vegetable garden, but it is out of the way enough that people won't be crossing any bee traffic. We probably won't see any action until spring, but we finally have our bee nest box up.

Western Bumble Bee Nest

When I went to clean out one of the bird nest boxes, I was surprised to find that a western bumble bee (Bombus occidentalis) had made its nest inside. Typically this kind of bumble bee makes its nest in the ground. But here was the clump of waxy cup-shaped cells described in the books nestled in the dog hair and sticks that the Bewick's wrens had been using to build their nest. (This could explain why the wrens decided to move out and rebuild their nest in the pot next to the back door.)

Alarmingly, all of the bumble bees, adults and juveniles, still developing in their wax cells, were dead. What killed them? Was is the cold weather snap we had in October/November? There was a garden spider in among the corpses. Had this small spider preyed on the bumble bee nest? I can't imagine that it could have gotten to the juveniles in their waxy cells. Was there some kind of mite or fungus that caused the death of all ages? I don't know.

During the winter the queen bumble bee hibernates in a protected location all alone. She will emerge in the spring to start a new colony and then usually die. I hope that there was at least one survivor from this western bumble bee nest. (More on bumble bees: xerces.org) Our native bees are vital pollinators and typically are not susceptible to the same diseases and environmental conditions that threaten European honey bees. Most are not aggressive and are not a threat to people.

We have noticed carpenter bees nesting in the yard before but this is the first time for bumble bees. I've wanted to create a native bee nesting site for some time. It seems now is the time to finally take on that project.

The Foundation of Habitat

Creating habitat for bird life means starting from the plants and working up.

A well-planted yard provides shelter for birds, but quality habitat requires natural food sources as well.

Native plants like this anemone not only provide shelter, they attract native insects.

When you think of an important pollinating insect you probably think of a honey bee. But the European honey bee is not native to California (or North America for that matter).

Locally we have several species of large carpenter bees and bumble bees that pollinate plants, but many native plants are pollinated by less glorified insects – flies, beetles and moths. You can see the fly feeding on the pollen on the lower area of the flower.

Most native insects can only feed on the pollen of native plants. These insects are important food for larger insects, lizards and birds.

Creating habitat for birds means establishing an environment safe for insects–flies and beetles, as well as the more beautiful butterflies. See crane flies.

Plants and arthropods are the foundation of habitat. Arthropods include insects, spiders and crustaceans (those little "c-shape" creatures that hop about on the ground when you lift up a pot, and yes, they are related to shrimp). Birds and lizards can establish thriving populations if your yard offers these vital resources. John Fitzgerald of Cornell University spoke last week in Los Angeles on bird conservation. He pointed out that the areas where eastern wood thrushes have declined coincide with areas of increased acid rain. The acidic rain kills the native crustaceans in the plant undergrowth, thereby removing an important food source for the wood thrush. Having a healthy population of creepers and crawlers, supports a healthy population of runners and fliers.

This western fence lizard not only eats its share of insects it also is makes your yard more healthy for you (fence lizard and Lyme's disease). Healthy fat lizards are also potentially a food source for red-shouldered hawks, shrikes and other birds.

If you want to help birds, you need to reexamine your ideal garden. Paradise isn't sterile. The Earth's garden is filled with abundance and diversity, including spiders, aphids and grubs.

Beneficial Wild Creatures In Your Garden

When my friend Douglas Welch of A Gardener's Notebook read the post about the benefits of western fence lizards in our garden, he proposed a joint effort on beneficial wild animals you should attract to your garden.

To find out why it’s important to attract this valley carpenter bee to your yard, read my post Beneficial Wild Creatures In Your Garden on A Gardener’s Notebook.