It has been several years since the 17-year cicadas returned. When are they due in the Chicago area again?

Dear Tom,

It has been several years since the 17-year cicadas returned. When are they due in the Chicago area again?

— William Montelli

Dear William,

The 17-year periodical cicadas last emerged here in the spring of 2007 and will next return in 2024. Their long life cycles are genetically driven, and weather is not a factor. The nymphs emerge from the ground in the spring of the 17th year when soil temperatures about 8 inches below the surface warm to 64 degrees. In the Chicago area, this usually happens in late May or early June. The 17-year life cycle of the periodical cicada makes it the longest-lived insect known. Adult female cicadas deposit eggs in the twigs of trees and large shrubs, after which, in six to 10 weeks, newborn nymphs drop to the ground and burrow in for 17 years, feeding off the juices of tree roots.