URBANA, Ill. — Illinoisans can expect visitors this spring, and University of Illinois Extension has a new website to help. Cicadas in Illinois (http://web.extension.uiuc.edu/cicadas/) contains information about the insects, including how they taste.

Prepared by James Schuster, U of I Extension horticulture educator, and Phil Nixon, U of I Extension insect specialist, the website covers the history, emergence and life cycles of the cicada varieties that visit Illinois. There are two types of cicadas commonly found in large numbers in Illinois. Dogday or annual cicadas emerge every year. Periodical cicadas emerge every 13 years in the southern half of the state and every 17 years in the northern half.

A cycle of cicada emergence is due this spring in northeastern Illinois. “Cicadas are sometimes mistakenly called locusts,” said Schuster. “In actuality, they are not related to locusts at all but are grasshoppers. The male cicadas ‘sing’ during the day to attract females.”

As cicadas inflict some damage to trees in the egg-laying process, homeowners are sometimes concerned about controlling the insects.

“The damage done to an established tree by the cicadas is not significant enough to justify trying to control the insect,” said Schuster. “Let nature take its course. However, it is suggested that new trees not be planted until fall to avoid cicada damage to their trunks.”

And nature provides a number of predators on cicadas, including birds and the cicada killer - a large wasp that catches the cicada, stings and paralyzes it, and drags it back to its chamber. The female lays its eggs in the cicada. When the larvae hatch, they feed on the still-living insect.

Cicada killers and birds will be pretty busy this spring in northern Illinois, if predictions hold true.

“The northern Illinois brood, which will emerge in late May 2007, has a reputation for the largest emergence of cicadas known anywhere,” said Schuster. “This is due to the size of the emergence and the research and subsequent reporting over the years by entomologists Monte Lloyd and Henry Dybas at the Field Museum in Chicago.

“During the 1956 emergence, they counted an average of 311 nymphal emergence holes per square yard of ground in a forested floodplain near Chicago. This translates to 1.5 million cicadas per acre. In upland sites, they recorded 27 emergence holes per square yard, translating to about 133,000 per acre. This number is more typical of emergence numbers but is still a tremendous number of insects.”

By way of comparison, Schuster added, a city block contains about 3.5 acres.

“When the cicadas start dying and dropping from the trees later in the spring, there are large numbers on the ground, and the odor from their rotting bodies is noticeable,” he said. “In 1990, there were reports from people in Chicago having to use snow shovels to clear their sidewalks of the dead cicadas.”

And, “yes, periodical cicadas are edible,” said Schuster. “Native Americans utilized them in their diet, and in 1990 several college students were filmed eating them. They reported they tasted like almonds.” The periodical cicada flies only a short distance, apparently less than one-half mile, from where it emerged from the soil. Therefore it expands its territory very slowly considering its long life cycle. We are not used to thinking of insect life cycles longer than one year. Only nine generations of 17-year periodical cicadas ago, Abraham Lincoln was practicing law in Illinois prior to the Civil War.

During the intervening time, periodical cicadas have probably spread only about five miles. Consider what most of Illinois was like before the 1900s. Large areas of prairie had periodic prairie fires that killed many trees. With prevailing west winds, large prairie fires would have moved east with the wind.

Rivers that run roughly north to south, such as the Fox, Des Plaines, Illinois, Rock and Mississippi Rivers would have functioned as firebreaks. Trees would have survived much longer on the east sides of these rivers, and so would the periodical cicadas.

As a result, we see higher populations of periodical cicadas in East Peoria than in Peoria, Rockford east of the Rock River, and similarly along other rivers.