ZOO-ology column: Roly-polys will surprise you
Nature is full of surprises. Some may not exactly rock your world, but might prompt a closer look at tiny creatures you commonly see.
Take Roly-poly bugs for instance - the little rollers that curl into a protective ball when touched.
The truth is roly-polys aren't bugs. In fact, they're more closely related to shrimp, crayfish and lobsters.
Take a better look; they have seven segmented plates that make up a hard, but flexible exoskeleton. They're land dwelling (terrestrial) crustaceans. They breathe with gill-like structures and need high levels of moisture and humidity but can't survive underwater.
So why are they called bugs? Maybe it's because of the company they keep. They're found worldwide with various insects/bugs; beneath logs, rocks, in mulched areas, gardens, in woods and other moist, dark areas. They're a specialized member of the woodlouse family, order isopod (identical pairs of legs). They may be mistaken for another isopod called a sow bug, but the sow bug can't roll up - it runs away.
Now if that's not exciting enough, did you know the females have a marsupium (brood pouch)? You're probably thinking kangaroo and opossum, but crustaceans carry their eggs. The roly-poly has two overlapping plates forming a pouch to incubate eggs. Once hatched, the young remain in the pouch for several days. They actually stay in family groups and can recognize each other through a chemical tag until the young are grown, in about a year.
Hard exoskeletons are molted as they grow. The rear part splits away first. A day or two later the front part is shed. So, if you should find a two-toned roly-poly, it's in the molting process. If you find one that's purple or bright blue, it can be a sign of an illness (iridovirus) affecting the species.
They also have blue blood. Red blood has hemoglobin with oxygenated iron ions, but roly-polys have hemocyanin with oxygenated copper ions that make blood appear blue.
Dinner for a roly-poly is a matter of leftovers. They're decomposers, eating decaying plant material, lawn clippings as well as fecal matter - their own included. They don't urinate, but release a form of ammonia gas. They clean up and aerate soil, replace nutrients and are beneficial to a compost pile. Being very sensitive to environmental conditions, roly-polys can be an indicator of the health of an ecosystem. They eat the eggs of stink bugs that may damage crops. Roly-polys are sometimes blamed for plant damage when they may only be an innocent by-stander. Remember, they eat mainly decaying matter.
Its many names include pill bug, armadillo bug, potato bug, doodlebug, wood louse and roller.
Pill bug probably refers to the rolled shape. Roller refers to the means of defense.
The sow bug and others that run away for protection are known as hikers.
The next time you move a flower pot or rock, take a closer look. You may find rollers snoozing there during the day, and they don't bite.
Roly-Poly Bug Facts | eHow.com
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Judie Farnsworth is a longtime volunteer at The Texas Zoo specializing in educational programs.