Nomada bees prey on the real pollinators
When I think of a bee, I imagine something fluffy and cute. But this bee doesn’t fit the image, looking more like a space rover, examining the terrain with thick antennae and marbled eyes. Although brown and yellow, from a distance the bee appears eerily translucent.
Last week I was kneeling on the eewie-gooey forest floor trying to photograph a community of tiny Andrena bees. The small sunny space was surrounded by salmonberry vines in full bloom. Salmonberry is a Pacific Northwest native that produces salmon-colored berries that look like raspberries and taste like dishwater. But the flowers are spectacular, a deep vibrant pink that attracts many early pollinators.
Identified by behavior
I knew this was a bee, not by its looks, but by its behavior. It was cruising above the aggregation of Andrena nests, surveying the lay of the land. Nomada bees are cleptoparasites on Andrena bees. The female Nomada waits for the female Andrena to leave her nest, then pops inside to lay an egg, or perhaps two or three.
Once inside the egg chamber, which the Andrena has been provisioning with pollen for her offspring, the Nomada lays her egg in the wall of the chamber, partly buried and partly sticking out. Later, when the Nomada larva emerges, it is fully equipped with a set of pincer-like mandibles and the ability to move fluidly through the chamber.
On a search and destroy mission
Systematically, this newly hatched larva destroys any egg it finds, including the host egg and any sibling eggs that may be in the same chamber. Then, with the competition out of the way, the larva consumes the pollen pellet at leisure. From then on, it behaves much like any other bee, developing into a pupa, and then into an adult. The adults emerge in the spring at the same time as the Andrena bees that survived.
In the early spring, the male Nomada bees stake out a territory over an Andrena community and lure females with pheromones. Once mated, the females are ready to invade the nests of their hosts. Although most Nomada species prey on Andrena, some species prey on other bees as well. The Nomada are members of the Apidae family, the bee family with the most cleptoparasites.
Although these bees collect nectar for energy, they have no interest in pollen beyond commandeering the pre-collected pellets from other bees. As such, they are very poor pollinators.
Nomada are easily confused with wasps
I was able to get only a single shot of the Nomada; all the other photos were closeups of dead leaves. So frustrating! Still, you can see what this strange creature looks like. As you can imagine, these bees are most frequently misidentified as wasps. Since they don’t collect pollen, their legs and abdomens are virtually hairless, a look that shouts “wasp.” In addition, they have spiky points on their legs, adding to the wasp-like appearance.
So go out and find one! If you can find a group of Andrena, you can surely find a Nomada to go with it. For reference, here are some photos of a different Nomada species from a prior post.
Honey Bee Suite
Note: Special thanks to the folks at Bugguide.net for confirming my identification.