The Bugs That Aren’t

By Gary Raham

You have probably seen pill bugs. These animals are bean-sized and gray or brownish in color. They are shaped like a jelly bean cut in half lengthwise.

Pill bugs are divided into many segments, which make them look like tiny armadillos. When you touch one of these bugs, it rolls up into a ball that looks like a pill. That’s why it’s often called a pill bug, even though it isn’t really a “bug” at all.

Pill bugs get their name from the way they roll up into balls, or “pills,” to protect themselves.  Photo (and above) by Chris Dietel

All true bugs are very different animals. They belong to a special group of insects. The pill bug is more closely related to animals like crayfish and brine shrimp. If you have pet fish you may have given them brine shrimp to eat.

The pill bug is also related to some of the tiny, darting animals you can just barely see when you look at a jar of pond water. All of these animals are crustaceans.

Look Closely
The pill bug is a great little animal to study up close. It can’t hurt you. It’s easy to find in many damp spaces under leaves and rocks. And it’s easy to catch because it usually rolls up instead of running away.

By rolling up, the pill bug covers up the soft underside of its body. That protects it against some spiders and centipedes, which are the pill bug’s usual enemies. The pill bug also has a taste that most spiders don’t seem to like.

If you hold a pill bug in your open hand for a while, the creature will gradually unroll, probably on its back. The pill bug’s back is so curved that it might not be able to turn itself over. It may wave its legs in the air for a while before resting.

Pill bugs are harmless and fun to watch. Be careful not to harm them. (Photo by Chris Dietel)

When the creature does stop moving for a moment, look at its tail end. A magnifying glass may help you to see two pairs of white spots near the last pair of legs. The pill bug breathes with these organs. The white color is caused by trapped air.

If you put a small drop of water on these “lungs,” you may see a tiny air bubble. This is where the pill bug breathes in and out. It also does a lot of breathing right through its skin.

Don’t keep a pill bug upside down too long. It can dry out quickly. In fact, drying out is a big problem for the pill bug.

The Wet Life
Most crustaceans live in water. Unlike insects, they do not need waterproof coatings to keep their bodies moist.

But pill bugs do not live in water. To survive, they behave in ways that save water. For example, pill bugs spend most of their time in moist places under rocks and leaf litter.

They tend to stay under cover during the day. They go out at night to eat spider’s eggs, dead plants, ripe fruit, and ant droppings.

If you lift up a rock and find pill bugs there, they are likely to be all bunched together. They prefer one another’s odor, and they like to be touching something on all sides. Bunching up also helps keep moisture from evaporating. The smell of other pill bugs is probably how they find their way home at night, too.

Little Sips
You can also watch pill bugs drink water. Place a pill bug or two in a shallow pan or dish. Put a small drop of water near the edge.

When they begin to dry out, they will lower their rear ends into the water and move them up and down. They are drawing water up between their tail “fins,” much like our way of sucking water through a straw. The water follows grooves along their legs, helped along by the movements of tiny hairs. The water ends up near their mouths, where they can drink it.

When you pick up a pill bug in the spring and summer months, you may find one whose underside looks milky. If you look closely, you may also see shadowy oval shapes.

The oval shapes are young pill bugs. They are in a brood pouch formed by flat plates that grow from the female’s legs. When the young are ready to leave, the mother pill bug will release them. They will look like tiny white copies of the adults.

Pill bugs have seven pairs of legs, unlike insects (three pairs) and spiders (four pairs). The four white ovals toward the bottom of the right-hand picture are the pill bug’s “lungs.”  (Photo by Gary Raham)

Young pill bugs live in a dangerous world. If conditions are too dry, the young will die. If the ground is too wet, they will be attacked by molds. The survivors will become more darkly colored each time they shed their skins and grow. After a year, they can produce their own young.

Old Beliefs
People used to believe many myths about pill bugs. Some thought that a pill bug in the house would bring bad luck. Others thought that feeding pill bugs to cows or people could cure stomachaches.

But pill bugs are just unusual crustaceans that have found a way to live on land. In fact, except when pill bugs munch on ripe tomatoes, these crustaceans and people get along pretty well.

The next time you see one, take a closer look at this tiny neighbor. Then let it wander off to take care of pill-bug business.