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Otto: Life or death drama: Wasp vs. spider

Published: Saturday, July 2, 2011 5:30 a.m. CDT • Updated: Sunday, July 3, 2011 12:33 a.m. CDT
Caption
(Provided photo)
A blue mud wasp is shown.

It’s not often that you get to witness life or death drama right here in the Tri-Cities. But there it was, happening right before our eyes, Sunday on my friend Lisa’s concrete patio.

That day, you might remember, was one of those summer days that make you really appreciate the season. The sun wasn’t too hot, the humidity wasn’t too high; in short, it was a great day to just sit and relax. Or so we thought.

Lisa was commenting on how her honey locust tree needed trimming when I saw a greenish-white form fall from one of the branches. As Lisa changed topics to weeding, I focused on the fallen object. What luck! It was a crab spider, one of my favorite summer arachnids.

As Lisa let go of any ideas she might have had on having a meaningful discussion about landscaping, I got up to inspect the spider further. And that’s when it happened. An ant – or, rather, what looked like an ant, to my 40-something eyes – came scurrying toward the spider.

The spider reacted as you’d expect a spider to – it attacked. That’s when I kneeled down for a closer look; it’s also when I realized just how wrong my analysis had been.

The “ant” was actually a blue mud wasp, a species that captures spiders to use as food for its young. The crab spider, therefore, wasn’t reacting offensively, but rather defensively, using every drop of its spidey strength to ward off the attacker.

The battle was quick; the victory decisive. The female wasp won with a quick injection of paralyzing venom. With the spider now helpless, though still alive, all the wasp had left to do was tote her prey back home.

But that toting was easier said than done. The crab spider, though not huge, was a solidly built creature. The wasp, by comparison, was spindly, with thin legs and a narrow waist. And her home, as it turns out, was quite a distance away.

Imagine finding a grand piano, then hauling back to your place, all by yourself. No hand trucks, no dollies, not even a strap to carry it with. That’s what the wasp was up against.

Taking the legs off a piano makes it way easier to move. As it turns out, it’s the same thing with spiders. The wasp, manipulating the crab spider’s body with her mandibles, systematically plucked six of the eight legs off, then began dragging her prize home.

As I watched the wasp move slowly along, I couldn’t help but admire her locomotion. She appeared to be up on her tippy-toes, no doubt to accommodate the spider’s bulk; but she also seemed to be using her wings to lift herself and her prey slightly, and facilitate her forward motion.

By the time the wasp made it up to the patio steps, Lisa had started reading a magazine, and I was getting cross-eyed from staring so intently. But the determined hymenopteran just kept moving along. As she neared the foundation of the Lisa’s house, she stopped, manipulated the spider some more, and removed the final two legs. Another 10 minutes of wrangling across the steps, along the foundation, then up under the siding, and wasp’s mission was complete ... for the time being. Her next duty would be to lay an egg on the paralyzed spider, then seal the two together inside a cell in her mud nest. The spider will stay “fresh” long enough for the young wasp to feed on it and develop, and begin the next generation.

I didn’t stick around long enough to watch that particular wasp leave her nest on another foraging flight, but I did see a different one near our Hickory Knolls maintenance garage – a structure that’s loaded with spiders. More life or death drama, waiting in the wings.

• Pam Otto is the manager of nature programs and interpretive services for the St. Charles Park District. She can be reached at 630-513-4346 or potto@stcparks.org.

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