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Outside » Natural World

No Such Thing as a 'Free Lunch'

Observing the cycle of life among butterflies and wasps and birds

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Just about everyone who reads, watches or listens to nature stories is familiar with the plight of monarch butterflies in the western U.S. Their numbers have dropped from millions to thousands in the last 20 years for a variety of reasons—mostly wrapped around habitat and their food plant, milkweed.

This Becker's White butterfly caterpillar is about to become food for an Oregon Sand Wasp. - SUE ANDERSON
  • Sue Anderson
  • This Becker's White butterfly caterpillar is about to become food for an Oregon Sand Wasp.

There I was over at Clarno, on the banks of the John Day River, visiting and delighting in the large milkweed growing operation the Bureau of Land Management and U.S. Forest Service have teamed up on, growing milkweed for replanting on their lands in hopes of producing hundreds of monarch butterflies. Can't beat that with a stick.

Imagine my horror when I was photographing a very beautiful, fat and healthy caterpillar on the milkweed, when suddenly a BIG paper wasp flew by carrying one of the caterpillars off. My first impulse was to knock the wasp out of the sky and save the caterpillar. Thank goodness I checked that action and just watched it go by, headed for its huge nest in a cottonwood right alongside the monarch garden.

As I watched the huge wasp nest, I could see other wasps returning with their prizes, so I got out my binocs and sat down at the edge of the monarch garden to watch the show. As I was observing it—the wasps coming and going—a magpie came flying through my field of vision. As I watched, it snatched one of the fully-loaded wasps out of the air.

That's when I was impressed with the old saying, "There's no such thing as a 'free lunch' in the world of nature."

Sure, when things are going smoothly, the caterpillar will be getting a free lunch from the plant (and the plant may be getting fertilized by the caterpillar's frass/poop). But then a wasp comes by, snatches up the caterpillar and hauls it off to feed its babies — AND then along comes the magpie who grabs the wasp out of the sky and hauls it home as food for its babies.

But then the pages keep turning, and along comes a bird hawk/accipiter who sees the magpie and decides it would be just the right thing to feed its young, and the tale goes on and on...

And, if a bird doesn't get the wasp, a fence lizard watching from a nearby rock may swallow the wasp, not bothered a bit by all the stinging going on—and then a kestrel comes along and grabs up the lizard to feed its hungry nestlings.

But let's go back to the wasp. The paper wasp is classified as a predatory wasp, in the vespidae family, known as killer wasps. They're very good at ridding a cash crop of insects that interfere with a farmer's trying to make a living, and way better than pesticides. And there's no chemical residue left lying around to kill everything else.

For a bigger caterpillar, wasps will use their stinger to subdue it. After feeding on it themselves, they'll roll it up into a ball and haul it back to their own kids for breakfast. For harmful larvae, such as the cabbage butterfly, for example, that's an end to the farmer's problem.

I've been told it's possible to purchase parasitic wasps from a garden shop, using them to destroy caterpillars causing serious damage. The wasps lay their eggs in caterpillars. When the caterpillar enters the chrysalis stage to become an adult insect, the eggs hatch, the larvae feed on the developing butterfly, then metamorphose into an adult wasp and exit through a tiny hole and fly off.

My wife Sue and I saw the evidence of that phenomenon back in the '80s when we brought 10 or so California tortoiseshell butterfly chrysalids home with us from a huge hatch near Tumalo Falls. We wanted to obtain emerging butterfly photos. However, we observed (and photographed) only jewel-like adult parasitic wasps emerging from the chrysalid cases, not the butterflies we'd hoped for.

While some garden supply companies sell parasitic wasps, they can become a serious pest when they build their big paper-like bag nests near people. Any perceived threat to the wasps's welfare will cause a lot of buzzing and stinging on humans nearby—and that makes everyone unhappy.

If you get bored with television, and the library hasn't got the book you want to read, take a hike out to the nearest tent caterpillar's nest, set your picnic chair and lunch close by and watch the action. But, remember, when the wasps complain about your presence and snack on your peanut butter and jam sandwich, "There ain't no such thing as a free lunch in nature..."

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