Facts About Arthropods

Arthropods make up over 90{1747bccc90d1a2d1e2199e0001317c300b96f720b9f4f5c4cc0560ba58ebd665} of the animal kingdom and they are everywhere. Well, just about everywhere. They live in the deepest parts of the oceans. They live on the highest mountain peaks. They even live on other animals, including you. They have adapted to live on land, in saltwater, in freshwater, below the ground and very likely in places we haven’t even contemplated might have life.

Emperor scorpion

Emperor scorpion (Pandinus imperator), the largest scorpion in the world. It also glows in the dark under UV light.
Arthropods have exoskeleton

An arthropod is distinguished from other animals by their exoskeleton, which means that their skeleton is on the outside of their body. Their bodies are divided into distinct parts with jointed legs and appendages, and they sport bilateral symmetry, making both sides of their body look the same; think of that spider that you saw in the bathroom as it scurried up the shower curtain.

Classes of arthropods

Insects are a class of arthropod. Like all arthropods, insects wear their skeleton on the outside of their body. Grasshoppers, butterflies, beetles, ants and bees are some examples of insects but there are approximately one million species of insect worldwide. However, all insects share some common body structure. They have three body parts; the head, the thorax, and the abdomen. They scurry about on six legs that are attached to their thorax. Depending upon the species, the adults may have one or two pairs of wings attached to their thorax or no wings whatsoever. They have two antennae and lateral compound eyes; that means their eyes are made up of many light-sensitive elements, each having its own refractive system and each forming a portion of an image.


Arachnids are a class of arthropod that you may have had nightmares about; yes, I’m talking about spiders, scorpions, ticks and mites to name a few of the known 65,000 species worldwide. Their bodies are segmented into two regions; the cephalothorax and the abdomen. They have eight legs and unlike insects they do not have antennae. Their mouth-parts are chelicerae (modified appendages), which are the fangs on spiders.


The class of arthropod known as crustaceans includes crabs, shrimps, lobsters, barnacles and 44,000 others worldwide. These interesting and sometimes tasty animals are primarily aquatic but there are some land dwellers among them. They have two body regions, two pair of antennae, and five or more pairs of legs.


Centipedes make up the class of arthropod known as chilopods. They tend to have a well-defined head, a flattened body, one pair of legs per segment and one pair of antennae. Although their name means one hundred legs, they can have significantly less or more than one hundred legs. The number of legs ranges from 30 to 342. However, regardless of how many legs they have, they never have one hundred because their legs are always in pairs and they never have an even number of pairs. But before you pick up the next centipede you see to count its legs, keep in mind that their first pair of legs are not used for walking but are modified into poison claws.


The last class of arthropod is diplopods; you probably know them by their common name, millipede. Sometimes confused for centipedes, millipedes are a little different. They have two pairs of legs per segment except for the first four segments, which only have one pair per segment. Like the centipede, they usually have a well-defined head and one pair of antennae. However, opposed to the centipede’s flattened body, the millipede has cylindrical-shaped body.

Arthropods are amazing

Arthropods truly are among us, just about anywhere you can think of, even in our nightmares.

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