Some insects curl up into a ball as a defense mechanism or to travel. These types of insects can be found in North America and Europe, as well as in Namibia. Generally, the insects will curl up to defend themselves from predators or irritants, but others curl up for locomotion, and can be seen traveling in a balled-up position.
Wood lice, known by many names including sow bugs and pill bugs, are found in groups in damp and covered areas. These insects have a hard layered shell, which looks something like armadillo skin, and 14 legs. These flat, 1/4" or smaller insects usually live under rocks or logs. They feed on vegetation and rotting matter and can be seen scurrying toward cover under rocks or leaves. When harassed, they ball up to protect themselves.
Cut worms curl into a "C" shape when unearthed or disturbed. They are the caterpillar stage of a flying insect, and are plant destroyers. You can find most species of cut worm on the soil surface or just below the soil line. They chew through stems of young plants and grow into soft, fleshy caterpillars of various shades of green, slate blue, brown or beige. Cut worms often have distinctive black spots on their sides. They can grow to be more than an inch in length, and some reach 2 inches.
Corn ear worms curl into a "C" shape when disturbed or uncovered. They are the caterpillar stage of a flying insect, and are known crop destroyers. You can find these worms on ears of corn, usually at the top of the ear. These worms typically are greenish or brownish in color and they have hair tufts and dark streaks down the sides of their body. Their size ranges from 1/4 inch to 1 1/2 inches.
Namib, or golden wheel, spiders roll into a ball to move. Found in the Namib Desert, these spiders fold their legs inward toward their body and use a cartwheeling motion to cover ground quickly. The spiders can travel this way, but primarily use the technique to escape from danger or threats, such as from their main attackers -- wasps. This burrow-dwelling spider hunts by foot rather than by web entrapment, and will take prey as large as a small lizard. The spider's coloring blends in well with its Namib Desert environment. The tarantula-shaped spiders have an alabaster body covered in fine hair with dark accent hairs.