Tom Turpin
Professor of
Purdue University







Joint-Footed Creatures


Biologists classify all living things into groups. The broadest classification is either plant or animal. These groups are called kingdoms and each kingdom is divided into subgroups called phyla.

On such phyla of the animal kingdom is arthropoda. The word arthropod is based upon the Greek term "arthro," which mans joint and "pod," which mans a foot. We find the same combining of terms in arthritis, an inflammation of a joint, and podiatrist, a foot doctor.

Arthropods are nature's joint-footed animals that possess a hard outer skeleton. The most prominent of the arthropods are the insects. Insects have three body regions: the had, thorax and abdomen. They also have six legs, two antennae and most have wings.

Crustaceans also are arthropods and include the water dwelling crabs, lobsters, crayfish and shrimp. Most have four antenna and appendages on segments of the abdomen.

Some arthropods are identified because they have many legs. The slow-moving millipedes are worm-like creatures that have four legs on each body segment. They don't have to be fast afoot because they feed on dead organic matter. Pillbugs, sometimes called sowbugs or roly-polies, are a type of millipede. Centipedes, on the other hand, move very fast. They are predators and must catch up to the other arthropods on which they feed. Centipedes have only two legs on each body segment.

The last major group of the arthropods is arachnida. Arachnids include the spiders, granddaddy longlegs, ticks and mites. All have eight legs, no antennae or wings, and only two body regions. Because of this, some folks say that spiders appear to have lost their heads. Spiders and granddaddy longlegs, also called harvestmen, are predators on other arthropods.

So there you have it, the family of insects. You might say that mites, ticks, crayfish, millipedes, centipedes, and insects are cousins. Some people don't worry about the relationship and lump all of the arthropods together under one heading. They call all of nature's joint-footed creatures "creepy crawlies!" And I don't think it could be considered a term of endearment.



Writer: Tom Turpin
Editor: Andrea McCann