An animal of class Insecta (or Hexapoda) of subphylum Uniramia of phylum Arthropoda. Generally, they have three segments to the body (head, thorax, and abdomen) with one pair of antennae attached to the first segment (the head) and three pairs of legs and two pairs of wings attached to the middle segment (the thorax). They are mostly terrestrial (though there are species which live in freshwater environments and in saltwater marshes). Note: centipedes, millipedes, spiders, and mites are not insects (though they are arthropods).