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The Swarm: Cicadas Emerge in Wisconsin

by Carijean Buhk, Urban Ecology Center

Outdoor concerts in Chicago have been rescheduled, wedding planners are searching for good sound systems, and “foodies” are looking for recipes all for the emergence of one little bug. Well, make that millions of little bugs. Brood XIII of periodical cicadas will emerge in Illinois and parts of Wisconsin this June. And just like the crowds at Summerfest, they’ll be loud and looking for love.

Immature cicadas, called nymphs, live underground for 13 or 17 years. Brood XIII is on a 17-year cycle. Nymphs attach to tree roots and suck the fluid to survive. As soil temperatures warm, the nymphs dig their way out and emerge en masse to climb trees in order to complete the final phase of their growing process. So many emerge at a time that predators like reptiles, birds, squirrels and even cats and dogs are unable to provide the usual population control found in other predator/prey relationships. There are just too many to eat. While hanging from branches for roughly four to six days, nymphs shed their exoskeleton, their wings inflate with fluid, and their new skin hardens. After that, the now fully-grown cicadas begin their short, above-ground life cycles with one goal – to find a mate.

It is the adult male mating calls that cause outdoor concert promoters to change their schedules. The calls from a group of cicadas sound something like a blender and can reach 90 to 100 decibels. This is between a power lawnmower up close (90 dB) and a chainsaw (100 dB). The males make this sound by flexing their tymbals, drum-like organs found on their abdomens. Females respond by flicking their wings.

After reproducing, the males soon die. The females live only long enough to lay hundreds of eggs in slits they create in tree branches. Six to eight weeks later, weeks after their parents have died, the eggs hatch, and the new nymphs drop to the ground and begin to burrow, starting the 17-year process over again.

Adult cicadas are black with red eyes, have yellow or orange stripes underneath, and are about an inch long with translucent wings. They are not harmful to humans or pets and do not sting or bite. Some people consider them a rare delicacy and are planning cicada-tasting parties. I’ve been told they taste like shrimp.

To learn more about these insects, visit Cicada Mania at http://www.cicadamania.com/cicadas/

Riverwest Currents online edition – June, 2007