Cicada Emergence Stages

by Carl Strang

The 2020 emergence of periodical cicadas in northeast Illinois is under way now. It has taken a while to get going and is running about two weeks behind the last main emergence in 2007. People have sent or posted reports from 28 towns or preserves so far in Cook, DuPage, Lake and Will Counties. I have begun to visit places where significant numbers of the insects have been reported.

The pattern is reminiscent of what we observed in 2007. A few individuals come out of the ground at first, then a few days later there may be a night that brings out many. It takes them a few days of recovery before the males begin to sing, few or countable numbers of Cassin’s 17-year cicadas in most places. So far only some of the more open residential areas have reached this stage. Forests lag behind because the trees retard the warming of the soil which triggers the cicadas’ emergence.

This Cassin’s 17-year cicada was the first I found in Wood Dale Grove Forest Preserve, the June 4 date well after they had begun appearing in open residential areas.

Where there are good numbers of cicadas, small choruses may develop in which there are too many Cassin’s to count. Such has been the case in 5 communities so far. The ultimate step, which to date I have found in only one spot in southwest Brookfield, has numbers of Cassin’s 17-year cicadas chorusing so loudly that it can be nearly painful to stand under them. Their chorusing produces waves of loud then softer sound on a regular rhythm, and they are joined by the second species, Linnaeus’s 17-year cicada, whose songs add a high-pitched overtone to the Cassins’ buzzing quality. When visiting that place in Brookfield I saw many cicadas on the ground, many nymphal skins, many holes in the soil, and a pair of mating Cassin’s. I saw a crow eating a cicada, but there may be too few predators in these residential neighborhoods to have much impact on this off-year emergence.

Many emergence holes and empty nymphal skins marked the high density area in Brookfield.

Mating pair of Cassin’s 17-year cicadas in Brookfield on June 5

I made the following sound recording in the same area. The surrounding Cassin’s choruses wash out the focal one somewhat, but you may be able to pick out the 6 waves of high volume spread evenly here (5-6 seconds between peaks in this 32-second recording). Also, listen for a few Linnaeus’s “pharaoh” calls along the way. They are not coordinated with the Cassins’ waves.

A visual rendition of the recording

6 Comments

  1. John Denk said,

    June 7, 2020 at 10:09 am

    In my yard near Tinley Park, I’m seeing lots of shed skins but only 2 adults so far. I have a lot of bird species in my yard, and I think they’re eating the adults almost as quickly as they emerge. I’ve heard two different calls in and near my yard but I need to brush up on the calls before I can identify the species.

  2. June 8, 2020 at 4:11 pm

    Carl check the Chicago Audubon Society Facebook Page and Facebook group for lots of sightings abc photos

    • natureinquiries said,

      June 9, 2020 at 7:00 am

      Thanks to you and so many others for your helpful alerts. I am following up as many as I can.

  3. jim247 said,

    June 8, 2020 at 7:31 pm

    In northeast Wheaton, we have quite a few. See (https://youtu.be/ubZPdxy-_q4).

  4. NancyCollins said,

    June 10, 2020 at 10:10 am

    Hi Carl, I’m confused. If the last emergence was 2007, why are there 17-yr cicadas emerging now? Thanks, Nancy.

    • natureinquiries said,

      June 11, 2020 at 6:08 am

      Hi, Nancy, scroll back a couple posts to where I outlined the history of this.


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