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When an Abundance of Wasps is NOT a Problem
Question. I have an organic garden and shun the use of pesticides. This has attracted many birds and insects, which has helped with pollination of flowers, fruit, and vegetables. However, in the past month, I've seen a huge rise in the number of wasps of all shapes and sizes. I put out two traps (which supposedly attract all types of wasps) – but neither has caught even one. I've looked for nests in the eaves of my house, but haven't found any. I read that some wasps nest in the ground, which makes me very nervous because my dogs roll around in the lawn. I would really like to bring the wasp population under control without the use of pesticides.
---Alexis in Sherman Oaks, California
Answer: Well, my first thought is to wonder whether this population NEEDS to be controlled. True wasps and hornets—like mud daubers and yellowjackets—are typically very aggressive and can be dangerous. But I'm always suspicious when emails don't mention anyone actually getting stung. So we emailed her back and asked directly if anyone has been stung. We also asked what the wasps are doing and to physically describe one or two types.
Her reply? "No one has been stung. Some of the wasps are very thin, with yellow and black stripes and long back legs; they float around the grass and are attracted to my flowers."
So—nobody being stung, no aggression, and visits to flowers all lead me to suspect that she has native bees, a huge category that includes familiar faces like bumblebees, but also creatures that don't look anything like our typical concept of a bee. There are several native bees that look like wasps—and others that look like flies, beetles and other insects.
I've seen dozens of different kinds of native bees in my own garden. And she's in California, so it's possible that she has species I've never seen; there's often a big difference in what kind of insects you'll find on opposite sides of the Rockies…
But this is all easy for me to say—I've gotten very used to native bees being gentle, non-stinging pollinators. (I was just outside picking raspberries while surrounded by dozens of huge bumblebees; a couple of them even buzzed me when I blocked their path to the new flowers, but I know they won't sting.) And she adds that her big concern is "the ones flying near the grass, which makes me think that they might be yellowjackets." I know for a fact that there are yellowjackets on the West Coast—and the Western yellowjacket is just as dangerous and aggressive as the Eastern ones who make our picnics close to impossible in August…
But my gut feeling is that if insects that look like yellowjackets aren't being aggressive, they're not yellowjackets. So I asked her to look at images of yellowjackets online to see if she thinks they match; and she found a picture online that she says is a perfect match with her lawn huggers. The colors are very yellowjacket-like, and the creature does have that distinctive skinny 'wasp waist'—but it also has VERY long back legs—clearly not a yellowjacket.
And now I have to admit to something between laziness and overwork—I was busy battling some really pesky weeds, and asked her to try and ID this unusual looking insect; which she was able to do pretty fast. Turns out it's an amazing creature known as a 'pollen wasp' that lives on the pollen and nectar of flowers, just like bees.
Now, in the past I've said that all wasps are carnivores—that they mostly eat other insects. And that just shows why you should never use the word "all" in this business. But these creatures are extremely unusual in the wasp world—almost unique. The Wikipedia entry on them notes that their behavior is much more like that of native bees than wasps. And it points out that "some California species bear a remarkable resemblance to yellowjackets".
So there are wasps that feed exclusively on pollen? Wasps that look like yellowjackets and act like bees? How did I not know this right away?
In my defense I'll note that some sources suggest that there may only be one true species in the entire country! (Most pollen wasps are found in or around South Africa.) And new discoveries are one of the best parts of this job! I was Editor of ORGANIC GARDENING magazine for seven years, will have hosted this show for 15 years in October, have written a half dozen or so books…
….and I still learn new things all the time. This is an amazingly diverse and interesting world; imagine: "Wasps that float like a yellowjacket and pollinate like a bee."