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26 September 2003

Spider Versus Wasps and Bees

by Forrest M. Mims, III
Geronimo Creek Observatory
Seguin, Texas

Often a cloud passes in front of the Sun while I'm in the field making the daily sky measurements. That's when I prowl through the tall grass and wild flowers to see what the local critters are doing. While a cloud was blocking the Sun last week, I came across a spider I've never seen before. The spider's abdomen was as green as grass. Its clear legs had yellow sections and were lined with black spikes. According to my spider book, this was a green lynx spider. The book said that lynx spiders are up to 5/8 inch across. But mine was closer to a full inch.

This green lynx spider dining on a bumble bee hasn't read the book that claims it catches only small insects. Photograph copyright by Forrest M. Mims III. Click image to enlarge.

According to the book, lynx spiders eats only small insects. My spider has not read this book, for it was dining on a bumble bee larger than itself. Spiders will sometimes catch honeybees in their webs, but I've never seen a spider catch a bumble bee. The irony of this is that bees are considered cousins of wasps, many of which are expert spider hunters. Open a mud dauber's clay nest, and you'll find as many as a dozen or so spiders in each cylinder.

After she builds a new cylinder, the wasp goes spider hunting. After she packs the cylinder full of paralyzed spiders, she lays a single egg on top. She then neatly seals the cylinder with pellets of mud scooped from the edge of a nearby puddle. Watch this step closely, and you'll hear a buzzing sound as she shapes the pellets. It appears as if the wasp switches on her wing muscles to cause her body to vibrate. This causes the pellets of mud to liquify, so she can form them into a perfectly shaped cap. Because the spiders in a mud dauber's nest are paralyzed by the sting of the wasp, they remain alive. This means the wasp larva than emerges from the egg has plenty of fresh food.

If you're patient, you can easily watch wasps hunting and even catching spiders in most any open place. Watch for a wasp flitting through the weeds or walking rapidly on the ground. She's most likely spider hunting. Recently I watched a large red wasp catch an even larger spider. The wasp clutched the spider in her jaws and began walking rapidly up a brick wall. After she was about 5 feet above the ground, the wasp lost her cargo. She then walked back down to the ground and searched until she found the spider. The wasp then continued her journey. This time she made it to the top of the wall and began walking sideways. After around twenty feet, she came to a small hole in the eave of the roof. She backed into that hole, pulling the spider in behind her.

Females are the hunters in the wasp tribe, and their victims are usually females, too. I've found male spiders in mud dauber nests, but not many. This is probably because male spiders are much smaller than their female counterparts. They hang around the web, stealing food the female catches, while waiting for their one big opportunity to get to know her better. It takes a big wasp to catch a spider as large as a tarantula. Years ago I was leading a group of teenagers on bicycles through a remote stretch of desert near Maljamar, New Mexico. We were fascinated by large black wasps that buzzed around the orange flags on our bikes. These were tarantula hawks. They stalk tarantulas much larger than they are. When they find one, they sneak up from behind and sting from below. They then dump the victim in a hole they prepare, lay a single egg on it and fill the hole with soil.

Tarantulas make good alarm clocks when you're on a bike trip with teenagers. If some of the riders want to stay in their sleeping bags by the side of the road, just catch a tarantula and hold it near the teen's face. I guarantee quick results. Tarantulas can be assertive when they want to be. When we lived in San Marcos, I noticed a large tarantula by the driveway as I was leaving on an errand.

That tarantula challenged me to fight by raising her front legs in attack posture. When I returned a few hours later, she was still there in the same posture. Evidently, the program in her brain that provided fight instructions had left out what to do if the opponent goes to the library instead. Next time you decide to kill a tarantula, you might want to reconsider. There are many tarantula keepers out there who will pay good money for a healthy specimen. One web site has more than 2,500 tarantulas in stock at prices of from $8 to $475, plus overnight shipping.

Forrest M. Mims III is vice-chairman of the Environmental Science Section of the Texas Academy of Science. He studies the ozone layer, sunlight, haze, water vapor, tree rings and airborne bacteria.

This feature was originally published in Forrest Mims's weekly science column in the Seguin Gazette-Enterprise, Seguin, Texas. The column is written for a general audience.