Wilderness Underfoot: Scorpions in ancient Illinois

StoryImage( ‘/Images/Story//Auto-img-118719907119992.jpg’, ”, ‘Eoctonus miniatus – A scorpion from Illinois coal forests, lived during the Carboniferous Period (300 million years ago). It’s shown here consuming an insect, Testajapyx thomasi. Less than an inch long, this diminutive scorpion bears a resemblance to scorpions we might find today in parts of North America. Scorpion fossils are very rare and highly prized. The remains of Eoctonus are found in ironstone concretions from coal spoils near Braidwood, Ill. Scorpion fossils were also among the finds in a pair of newly- discovered caves with limestone deposits from the Carboniferous Period. These caves are southwest of Chicago. Although scorpions first appeared much earlier, our best fossils are all Carboniferous age.‘);
StoryImage( ‘/Images/Story//Auto-img-118719914816451.jpg’, ”, ‘The striped bark scorpion — our state’s only modern scorpion – also known as a plains scorpion, Centruroides vittatus is found in Monroe County, south of East St. Louis. This small scorpion crawls around the bluffs region near the Mississippi River. It is mostly harmless, with a sting about as painful as a wasp’s sting. It’s venom causes burning pain and a welt, and local numbness that goes away in an hour or two.‘);

Scorpions are extremely rare in the Great Lakes region, but during prehistoric times, they survived here for well more than 200 million years.

They were the first group of arachnids to appear on earth, and among the earliest animals to walk on land. The ancient scorpion line broke off from a group of animals called Eurypterids or sea scorpions.

The earliest scorpions were, indeed, seabound creatures. They had gills for breathing underwater, and their legs weren’t quite as sturdy as those of later land-dwelling species. Throughout the Devonian Period, beginning about 443 million years ago, scorpions evolved a wealth of new species. By the Carboniferous Period, about 100 million years later, fully terrestrial scorpions had appeared, many of them looking much like modern scorpions that we see in North America today.

Since those times, the body plan for scorpions has remained relatively consistent. Every scorpion has a five-segmented tail ending with a stinger. The stinger contains a pair of poison glands that deliver painful stings, but unless you’re highly allergic, only one U.S. species (the bark scorpion found in Arizona) is considered deadly. On the front of the scorpion are its pedipalps—the large limbs that bear its pincers. These pincers are used for hunting, defense and territorial fights. Between the pedipalps, you’ll see a pair of mouthparts known as chelicerae. A scorpion may have as many as six pairs of eyes. And, like spiders, it has eight walking legs.

Today, there are more than 1,500 species of scorpions in the world, 70 of which live in the U.S.

from the Aug 15-21, 2007, issue

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