Most insects have wings at one time or another in their lives, although a very few species, such as fleas, silver-fish, firebrats and springtails, do not. Flying insects have two pairs of wings — forewings and hind wings — although not all of them use both pairs for flying. All insects have a tough outer skeleton, six legs and bodies divided into three distinct parts, but there is enormous variation between insect species. Most insects do have wings. Fleas, lice, silverfish, and firebrats are the only truly wingless insect groups that most of us are familiar with. Most adult insects have two pairs of wings, but they’re not always visible. Often they’re hidden, shortened, or nonfunctional. You can easily see both pairs of clear wings on wasps, bees, ants, and termites. Their wings are held on top of their backs and the back pair is usually smaller than the front pair.
A beetle doesn’t appear to have wings at all, yet the hard outer covering on the back of a beetle is actually a pair of modified wings. The second pair of clear, membranous wings are folded up underneath. When a beetle flies, the wing covers, or elytra, spread apart at the center and the flight wings beneath unfold. It all happens so fast though that you can rarely see it happen.
In moths and butterflies, the forewings and the hindwings are covered with scales that create patterns and colors. Cockroaches, grasshoppers, and crickets have flight wings hidden under a leathery pair of front wing covers that match the rest of the body. Files are the only insect group that has only one pair of functional wings. The hind wings are reduced to small, knobbed structures called halteres that act like little gyroscopes to help the fly keep its balance.
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