Answer Man

Invasion of the crawdads digs into reader’s yard

A crayfish built this mini-volcano out of dirt.
A crayfish built this mini-volcano out of dirt.

Q. In the past few months, I have noticed mounds of dirt that look like mini-volcanos with a small hole at the top. I find them in the lower areas of my backyard, which stay wetter than other places from the rain runoff in my neighborhood. Do you have a clue what these are or what is making them?

— Mike Koziatek, of Belleville

A. Remember the 1990 Tom Hanks movie “Joe Versus the Volcano”? Well, you might have a possible sequel in “Mike Versus the Crawdads.”

Not being a student of nature, I initially thought it odd that you’d find crayfish, crawfish, crawdads, mudbugs or whatever you want to call them in an area without a pond, creek or other body of water. But our expert in all things outdoors — Dr. Charles Giedeman — only had to glance at the pictures you sent to instantly recognize your invader as the crayfish.

According to the Carnegie Museum of Natural History, the Cambarus diogenes (devil crayfish) is one of 23 species of crayfish found in Illinois and possibly the one that most closely fits your habitat. While the digger crayfish (Fallicambarus fodiens) also can produce the telltale volcano-like stack, it is primarily aquatic but sometimes digs burrows out of the water. On the other hand, the devil crayfish spends most of its time in the burrows it digs.

If you want to see what is living under your grass, you may have to go to http://iz.carnegiemnh.org/crayfish/NewAstacidea/species.asp?g=Cambarus&s=diogenes&ssp, because they’re generally nocturnal. So while you’re sleeping, they’re digging away, pushing up muddy soil out of their burrow as they shape that small volcano with the neat little hole on top.

You may be wondering (as I was) how a “fish” can live out of water. As it turns out, burrowing seems to be a good strategy for crayfish, according to Tom Pelletier, who holds a master’s degree in biology and answers questions at askanaturalist.com. Crayfish all over the world have developed a similar lifestyle of digging complex burrows down to damp or wet soil. Like all crayfish, the devil variety has gills in its abdomen under its shell. These gills are capable of taking oxygen from the air as long as they are wet, which is why the crayfish like the swale in your yard because it likely stays extra damp.

As you might expect, crayfish are classified with the clawed lobsters (Nephropidae). There are more than 600 species of the creatures around the world, with the Tasmanian Giant Crayfish holding the title of the largest freshwater invertebrate anywhere, growing in some cases to more than 30 inches long and packing up to 11 pounds.

I can only imagine what kind of “volcano” you’d find in your yard with something like that digging around. See one at http://yhsbiology.wikispaces.com/Crustacea or on wikipedia.

Q. Is it true the hydrangea is the official flower of Belleville?

— Steve Suess, of Belleville

A. To Rick Effinger at Belleville’s Effinger Garden Center, it deserves that honor by sales alone. Roughly 10 to 15 years ago, residents here went crazy over the PeeGee variety, so called because of its botanical name, “paniculata grandiflora.”

“It was a hot one,” he told me. “We sold tons of them — mainly downtown in the historical area. They put them all up in there, and they called it the Belleville bush. Someone told me once that it was official, but I’m not really sure of that.”

Neither am I. While it was wildly popular and, according to Effinger, may have gotten a boost from the St. Clair County Historical Society, it may be one of those urban legends. Nobody I’ve talked to can confirm that it ever gained “official” status by ordinance or proclamation, although I’d be happy to hear from anyone who can. Since then, PeeGee sales have cooled in favor of the Limelight and the Annabelle with their various shades of white and pink, Effinger said.

“They’re really a great summer bloomer,” Effinger said. “(Fox2 meteorologist) Dave Murray has Limelights all in front of his white picket fence at his home. I’ve taken that same idea and had some people do it as a divider between two property lines. They said it is stunning when it blooms.”

Today’s trivia

On which two continents would you find no crayfish?

Answer to Wednesday’s trivia: Straits are usually naturally formed, narrow, navigable bodies of water that connect two larger bodies of water. The longest is often considered to be the approximately 500-mile-long Strait of Malacca that runs between the Indonesian island of Sumatra to the west and Malaysia and extreme southern Thailand to the east. It gets its name from Melaka, an important port on the Malay coast in the 1500s.

Send your questions to Roger Schlueter, Belleville News-Democrat, 120 S. Illinois St., P.O. Box 427, Belleville, IL 62222-0427, rschlueter@bnd.com or call 618-239-2465.

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