How Cicadas Work

Know 'em When You See 'em

Why are cicadas so noisy?
Why are cicadas so noisy?
Photo courtesy Dave Davis/EPA

Cicadas are often mistaken for locusts, but they're actually more like leafhoppers or aphids. They are classified in the order Hemiptera -- a distinction given to all insects with piercing and sucking mouthparts. Entomologist have identified 1,500 different species of this mythical insect [source: Encyclopaedia Britannica].

The average wingspan of a cicada is between 2.5 centimeters and 15 centimeters (1 and 6 inches), depending on the type. The periodical variety are notoriously bad flyers (good thing they don't have to pass a flying test!), and they often run into things, if they can get off the ground at all. Why should they run, after all, when there are so many of them hanging out at once? They have four wings, and when they're not flying they fold their wings back along the sides of their body. The glassy, transparent, longer forewing covers the shorter, opaque hind wing. A network of sturdy veins strengthens the two pairs of wings.

Cicadas have three pairs of legs, all about the same length. Consequently, they aren't adept at jumping, though they do try. Large, compound eyes situated on each side of their head give them wide peripheral vision. Three tiny eyes on the top of the head (called ocelli) allow them to watch for predators from above. Small, bristle-like antennae are located just behind the ocelli.

The cicada's mouthparts are enclosed in a long, thin, beak-like sheath. The sheath, called the labium, is retracted between the legs when the insect is not feeding. The labium contains four needle-like stylets used for feeding. Cicadas feed by piercing the surface of plants with their stylets. They use them like a straw to suck up the sap from plants.