There is a strange, very loud sound in the trees on campus at this time of year. It normally begins at dusk, but may sometimes be heard during hot afternoons. The sound is a moderately high pitched “weeee-ou, weeee-ou, weeee-ou” buzzing sound that increases in intensity then fades away.

This the mating call of the cicada. It is often erroneously called a locust, but it doesn’t hop about as do the grasshoppers and crickets, preferring instead to fly quickly then sit still. Cajuns call them cigale de bois (meaning mosquito hawk of the woods, or cigale de nuit (mosquito hawk of the night).

Our local annual cicadas have rather simple life cycles. Females lay their eggs in tiny slits they cut in twigs with their ovipositors, a sharp appendage at the end of the abdomen. The juvenile stage, called a nymph, reaches the ground when the twig it is in falls or when it falls as it crawls about on the tree. The nymph burrows into the soil and feeds on the juices of roots. When it matures, the nymph exits the ground and climbs the nearest tall object. This is frequently the same tree were its mother deposited her eggs, but it may be a house wall, garden rake, or a lawn chair. At some point, the nymph stops, its outer skin splits down the back, and it emerges in its adult form. After sitting a spell and allowing its wings to unfurl and harden, it flies away and begins looking for a mate.

The males have organs on the bottom of their thorax (the second section of the body) that produce their love song. The chorus of sounds is a signal for other males to join in and for females to visit and choose a mate. Each species (there are more than 75 species in the eastern U.S.) has a unique call and it is fun to try to distinguish one from another.

The length of time between egg and adult varies with the species. One of the most widely known is the “17 year locust,” but the local cicadas are generally three year forms. There are cicadas emerging each year during July and August, so there are basically three breeding populations. Each summer when you hear fresh adults singing, there are one and two year old nymphs in the ground.

If you hear cicadas calling on campus or in Audubon Park, see if you can find cast skins (called exuvia) of recently transformed nymphs. A tell tale sign that they are around is the presence of perfectly round holes, about the size of a thimble, in the ground from which they emerged.

If you haven’t heard cicadas, visit Thomas Hall at dusk, or take a walk in Audubon Park.