How are insects different from spiders and centipedes?

Insects have three pairs of legs or six legs. spiders have four pairs or eight legs and since centipedes have more then six legs, they are also not considered insects.

For insects, they have three pairs of legs or six legs. On the other hand, spiders have four pairs or eight legs. Spiders and insects also have a difference when it comes to their major body parts. Spiders only have two main body parts while insects have three main body parts.