The name comes from the Ancient Greek arthron meaning joint plus pous meaning foot because these animals are distinguished by their jointed limbs.

Arthropods are invertebrates which are covered with a tough, resilient exoskeleton made of cuticle having an outer layer consisting of chitin. ² The body consists of segments, each containing a pair of appendages, with each body and limb section encased in the hardened exoskeleton. The joints between the segments are covered by flexible cuticle.

Arthropods are bilaterally symmetrical with some of the species having wings. Also, the arthropod body consists of segments, each containing a pair of appendages. Too, for these animals to keep growing, they must go through stages of moulting, which is a process of shedding the old exoskeleton after growing a new one that is not yet hardened. The moulting cycles continue until the arthropod reaches its full size.

The Arthropoda phylum includes four separate class divisions: arachnida; crustacea; insecta; and myriapoda.

EX Extinct

EW Extinct in the Wild

CR Critically Endangered

EN Endangered

VU Vulnerable

NT Near Threatened

CD Conservation Dependent

LC Least Concern

NL Not Listed

The Arthropoda class Arachnida consists of over 100,000 species (2018) and includes: barrel spiders, harvest spiders, horseshoe crabs, mites, pseudoscorions, scorpions, spiders, ticks.

The Arthropoda class Crustacea consists of over 67,000 species (2023) and includes: barnacles, brine, crabs, crayfish, king crabs, krill, lobsters, prawn, shrimp, slaters, water fleas, water lice.

The Arthropoda class Insecta consists of over 1.25 million species ¹ (2023) and is the most diverse group of all other animals groups, not just those in the phylum Arthropoda, which number of species represents more than half of all known living organisms. Amazingly, the total number of living species in the class Insecta is estimated to be upwards to as many as ten million, which is potentially amounting to over 90% of all different life forms on Earth.

This is a group of invertebrates that have a chitinous exoskeleton, a three part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae.

The class Insecta includes: ants, aphids, bees, beetles, bristletails, butterflies, cockroaches, crickets, earwigs, fleas, flies, grasshoppers, dragonflies, lacewings, lice, mayflies, moths, stick and leaf insects, stoneflies, stylopids, termites, thrips, true bugs, wasps, and web spinners.

The Arthropoda class Myriapoda consists of over 13,000 species (2023) and includes: centipeds, millipedes and other small myriapods.

The name comes from Ancient Greek work murion meaning ten thousand plus pous meaning foot. As if there was a need for it, the scientific study of myriapods is myriapodology, and those who study myriapods are myriapodologists.

Myriapods have a single pair of antennae, and usually simple eyes, however, a few of the species are eyeless.

Myriapods breathe through spiracles that connect to a tracheal system similar to that of insects. There is a long tubular heart that extends through much of the body, but usually few, if any, blood vessels.

A few species are able to produce and emit light and therefore are bioluminescent.

The majority of myriapods are herbivorous, except for the centipedes, which are nocturnal predators.

Myriapods are most abundant in moist forests, where they fulfill an important role in breaking down decaying plant material, although some live in grasslands, semi-arid habitats, deserts and a small few live along the sea shore (littoral).

All of the Myriapods are terrestrial and can be found in the soil of all continents except for Antarctica.

Chilopoda, centipedes, (3,300 species)

Diplopoda, millipedes, (12,000 species)

Pauropoda, small myrapods (830 species)

Symphyla, garden centipedes (200 species)