Field Notes

17-Year Cicadas: Gone But Not Forgotten

If you felt a little let down by the much-heralded periodical cicada emergence this June, here’s some validation. According to entomologist Gene Kritsky, author of Periodical Cicadas: The Plague and the Puzzle, “the general impression is there were fewer cicadas than last time.” “But,” he added, “I have no metric to verify that.”

What he and other scholars do have are estimates for particular areas, which they hope will lead to better understanding of emergence trends. Elmhurst, for example, was crawling with cicadas. The city tallied 200 bugs per square meter, recording where the insects did and did not appear.

Cicada hunter John Cooley, a University of Connecticut entomologist, gathered data on how this brood, Brood XIII, was distributed from central Iowa through Chicago Wilderness. He put more than 5,500 miles on his Explorer and another 2,000 miles on a rental car while a mechanic was fixing the Ford’s busted fuel pump.

Cooley stopped his car every tenth of a mile in likely cicada areas, shut off the engine, and listened out the open window, recording call densities. Besides establishing a baseline for comparison with future emergences, he said, “We’re also looking for how the different populations interact” where they overlap.

One reason the researchers give for fewer cicadas in 2007 is that many thousands had already shown up four years earlier. These early Brood XIII cicadas, which emerged in some suburbs, may have jumped the gun in response to the only known predator specific to the cicadas. The parasite Massospora cicadina shares the cicadas’ 17-year life cycle. That, said Kritsky, has led scientists to theorize that the early risers did so “to get out of synchrony with the fungus.”

One of the spots hit hardest by the fungus was the Raccoon Grove Nature Preserve near Monee. Back in 1956—four emergences ago—the preserve had the highest cicada densities reported anywhere, up to 1.5 million per acre. This year? “None to speak of,” said Scott Haulton, wildlife ecologist for the Forest Preserve District of Will County.

Deforestation from farming, building construction, and other development likely also impacted cicadas. Insects in recently developed areas, for example, would have had a hard time surfacing where a parking lot had been poured.

To the wildlife that eat them, the insects were a long-awaited, life-giving feast. Birders reporting on the IBET listserv (Illinois Birders Exchanging Thoughts) observed more than 60 bird species chowing down on cicadas this summer.

The effect on populations was most noticeable for cuckoos, said Judy Pollock, bird conservation director for Audubon–Chicago Region. In previous years, the most black-billed cuckoos seen on the Bird Conservation Network’s regional breeding bird count was five. That number jumped to 13 this year. For the yellow-billed variety, the increase was even more striking—from 14 to 48.

Many birders enjoyed the sight of cedar waxwings snatching cicadas in midflight. Even failed efforts provided amusement. “I was at Wright Woods in Vernon Hills and saw a grackle pretend to be a flycatcher,” said Sheryl DeVore, editor for the Illinois Ornithological Society. “He missed.”

Fish also boosted their numbers by scarfing down the bugs. “Particularly trout and bass,” said Phil Nixon, entomologist for the University of Illinois Extension. “It was a bad time to go fishing. The fish were so stuffed with cicadas they couldn’t care less about a lure.”

Mice also went after the insects, a better source of protein than grains. “Domestic dogs and cats, weasels, skunks, otters, raccoons, possums, and coyotes all do well on cicadas,” Nixon said. Cicada-fed population booms will be temporary, he noted. More predators will be born, but many of the new animals will have a hard time finding food this winter.

Plants that ordinarily are eaten by birds benefited too—or did they? Some naturalists reported seeing branches unusually heavy with serviceberries in June. “Usually robins and cedar waxwings are all over those trees,” said Pollock. “This year the berries just sat in the trees. Birds go for the protein rather than the carbohydrates, especially during the breeding season.”

But as Nixon pointed out, serviceberries may well suffer a net loss. Especially if humans eat what the birds spare, the plants’ seeds won’t be spread.

Mark Hurley of the Lake County Forest Preserves wonders if the cicadas’ seeming drop this year means their 2024 emergence will be a ho-hum event. But he, for one, wasn’t at all disappointed by this year’s coming-out party. “I’ve heard there can be 40,000 cicadas per tree, and I wouldn’t be surprised if that were true here in Ryerson Woods,” he said. “Some evenings, he added, “literally the ground was moving.”

— Gary Wisby

Related Article:

Festival of the Cicadas, CW Spring 2007

17-Year Cicadas Appear, A Few Years Off Cycle, CW Fall 2003