Invertebrates – arthropods

Invertebrates are animals without backbones. They include annelids, nematodes, molluscs and arthropods.

Arthropods are an important phylum of invertebrates. They have:

  • a hard exoskeleton (their skeleton is on the outside rather than on the inside)
  • a segmented body (their body has different sections)
  • jointed legs

Arthropods can be divided into different groups depending on how many legs they have.

Arthropod groups and number of legs.  Insects have 6 legs. Arachnids have 8 legs. Crustaceans have 10 to 14 legs and myriapods have at least 20 legs