As of 2015, there are currently over one million known species of insects in the world, and scientists still discover new species on a regular basis. Some estimate that there may be between six and ten million species worldwide. Despite their vast numbers, all insects share the same physical characteristics.
All insects have six legs, two antennae and three body segments (the head, thorax and abdomen). All insects are cold-blooded, meaning that their body temperature depends on their surrounding environment. They are also invertebrates, meaning they do not possess a backbone. Most insects go through a life cycle that progresses from egg, larva, pupa and adult.
Despite similarities, spiders are not insects, but rather belong to a group of eight-legged invertebrates called arachnids.