Periodical Cicadas’ 2020 Emergence

by Carl Strang

In the previous post I outlined the history of DuPage County’s periodical cicadas. Part of that story remains to be told, and this next month will reveal much.

Newly emerged periodical cicadas

Huge numbers of our two species of periodical cicadas emerge every 17 years. The last major emergence was in the spring of 2007, so the next one will be in 2024. At least as far back as 1969, however, there has been a significant appearance of the cicadas four years early. This has happened every cycle since, in 1986 and in 2003. Will 2020 bring another instance?

This phenomenon first was noted by Henry S. Dybas, a biologist at the Field Museum of Natural History in Chicago. He invited observers to report locations where the cicadas were emerging in 1969. Illinois extension entomologist Phil Nixon followed suit in the next two cycles. These generally were not quantitative records, however, and no one noticed whether the cicadas were reproducing.

Towns where periodical cicadas were reported to Phil Nixon in 2003

As the map shows, most of the locations were in eastern DuPage County, adjacent Cook County, and extending southeast from there to the southern Cook border. I want to repeat this mapping in 2020, with two important modifications: a quantitative aspect, and an effort to document egg-laying. The question that needs to be answered is whether these early emergences are independent of one another. In other words, have they simply represented mistakes by a few individuals each time, emerging after 13 years of development rather than the usual 17? Alternatively, do these cicadas represent a new, splinter population of cicadas whose ancestors emerged four years early at some point, but ever since have reverted to the usual 17-year lifespan and are reproducing each time?

I want to compile site observations with maximum numbers of cicadas observed at each place: counted numbers where they are few, or massed numbers where there are too many to count. Each location also could have one or both species, readily separated by their different-sounding songs. Places with only a few, countable cicadas are worth mapping but have little biological significance, as the insects are munched on by every predator larger than themselves and few if any will survive to mate and lay eggs. The best possibility for an ongoing, separate population will be in places, if there are any, where massed numbers locally overwhelm the predators so that significant reproduction can happen. This is where observations of mating and especially egg laying are important.

Cassin’s 17-year cicadas mating. The area between the red compound eye and the base of the wing is all black in this species. In the slightly larger Linnaeus’s 17-year cicada there is an orange line connecting the eye and the wing.

This female is laying eggs. You can just see the ovipositor that has levered out from her abdomen and is piercing the twig.

The cicadas produce visible rows of slits on the undersides of twigs when laying eggs. This often kills the twig, so that leaves beyond the oviposition site turn brown.

I welcome shared observations to help me in this process. Already in April the nymphs have begun to tunnel to the surface. I suspect this allows them to monitor conditions aboveground so that they can know when best to emerge. Cicadas should begin singing in mid- to late May and continue through much of June, peaking in the first half of June. Location information to report is town plus nearest intersection of streets (or name of park or preserve if relevant). The Cassin’s 17-year cicada song is a rapidly clicking buzz that rises and falls, as with the single individual in this recording:

The Linnaeus’s 17-year cicada song is more of a tone rather than a buzz, starting high and descending, often rendered “pharaoh.” The next recording is of massed songs of Linnaeus’s periodical cicada. I don’t have a good recording of a single cicada singing:

Finally, here is what massed songs of both periodical cicada species together sound like:

Sound recordings and photos will be helpful, especially photos of ovipositing individuals and of twigs with egg damage. Naturally I will be making as many observations as possible myself and will follow up reports of massed cicadas. You can either send me information by e-mail to wildlifer@aol.com, or post your observations on the Insects and Spiders of Illinois Facebook page.

14 Comments

  1. Michael Whelan said,

    June 5, 2020 at 9:31 am

    Emerged in Naperville. Chicago Ave and Olesen Lane (Northeast side)

    • natureinquiries said,

      June 6, 2020 at 6:42 am

      Thanks!

  2. Lucie Prebel said,

    June 5, 2020 at 5:43 pm

    I was wondering why the ones I hear now in Oak Park sounded different. Living in the city I have really heard only 2 cicadas yearly so I never heard this before.

    • natureinquiries said,

      June 6, 2020 at 7:14 am

      The periodical cicadas have distinctive songs, different from the ones you hear later in the season.

  3. R. O'Malley said,

    June 6, 2020 at 11:49 am

    They’re out in Evanston today.

    • renee scudieri said,

      June 7, 2020 at 11:12 am

      Emerged in LaGrange 47th and LaGrange Road. I believe I hear both kind of cicadas. Quite a few around and pretty loud

  4. Jeff Westbrook said,

    June 6, 2020 at 3:33 pm

    Downers Grove, Blanchard and Brookbank. I’ve seen individuals all week on walks but today is the first day of that lovely racket.

  5. June 6, 2020 at 11:25 pm

    As a Chicagoland Treestorian. I may be one of the most passionately interested observers intensely collecting statistical data sets in order to determine and document what detrimental effects had been recently caused by urban and rural forestries costliest human-induced natural disasters resulting from man’s untimely introduction of emerald ash borer to the Americas.

    Our regions two native squirrel species had already faced disaster head on when Cook county alone lost 13 million ash trees all within a biblical and scope 6 years.

    Living ashes had specifically been local squirrel families most primary utilized tree species for building multiple nests within because of fraxinuses Stout opposite branching structure.

    Unfortunately because peak tree removal season unfolds during height of winter. Great numbers faced sudden eviction personally witnessed scrambling to backup nesting sites.

    2002 satellites and ground surveys had officially listed Ash credited with producing largest contribution of living green just behind grasslands.

    Surveys of urban settings revealed fact that individual green and white ash made up 75% of Northeast Illinois communities maturing heritage class tree collections between ages of 90 &160.

    Such unprecedented losses of maturing local tree populations in fact surpassing previous losses of 600000 elm trees to Dutch elm disease.

    Will obviously be expected to play a primary role possibly detrimentally affecting regional 13 year cicada population numbers this very minute waking up from nymph tree root suckling hibernation stages.

    Possibly setting future precedence facing upcoming 2024 brood populations.

    Thus here is a once-in-a-lifetime opportunity to responsibly do our part on behalf of… Well you fill in the blank here y’all.

  6. Doug Kuehnle said,

    June 7, 2020 at 10:04 am

    Singing like crazy in LaGrange. June 7th
    Willow Springs Rd and 47th street.

  7. Urs Geiser said,

    June 7, 2020 at 1:36 pm

    Lots of them in my yard this morning (6/7/2020), also many exuviae. Far north side of Woodridge (DuPage Co.), not far from I-355 and 63rd Street.

  8. June 11, 2020 at 10:11 am

    […] Photograph any behaviors of reproduction or oviposition you are observing (see here for examples of […]

  9. C Brejcha said,

    June 16, 2020 at 12:05 am

    There are a significant number of cicadas in Olympia Fields. Singing has been going on for several weeks. 6.15.2020. Near Western ave and Rt 30 and Olympia fields CC

  10. Rebecca said,

    June 26, 2020 at 7:14 am

    We had hundreds of what seems to be Cassin cicadas emerging and buzzing in our backyard this may/June. We saw a few mating and many being devoured by birds doing amazing swooping catches mid air! Then when we had those cold days a week or 2 ago, they seemed to abruptly vanish. I expected them to be singing and mating longer, and we expected to see lots of dead ones after egg laying, but we haven’t seen any at all since the cold snap! What happened? We’re in Bensenville near York and Grand.

    • natureinquiries said,

      June 27, 2020 at 6:42 am

      The Bensenville emergence was more limited this year than it will be in 2024. Your area is around the south end of that emergence zone, so the cicadas still may be on the rise there.


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