According to the experts, 2024 will be an eventful year with the emergence of two periodical cicada broods across most parts of the state. Cicada expert Catherine Dana, an affiliate of the Illinois Natural History Survey at the University of Illinois Urbana-Champaign, spoke with News Bureau life sciences editor Diana Yates about what to expect from cicadas in the year ahead.
How is 2024 different from recent years for cicada abundance and timing?
We have two large broods of periodical cicadas emerging in Illinois this year; one is a 17-year brood, and the other is a 13-year brood. Co-emerging broods aren’t that rare given that almost every year a different brood will emerge across the US. What is rare is that this only happens with Brood XIII and Brood XIX every 221 years. I have been looking forward to this for many years!
We often base our family vacations on where cicadas are emerging: 2021 was in Indiana, 2020 we traveled to see the off-cycle Brood XIII in Chicago, in 2019, we went to Ohio and Pennsylvania, for example. There are records of 22 different species of cicadas in Illinois. The typical “dog day” cicadas of the genus Neotibicen emerge in early July. We can hear their singing starting in July and continuing as late as October.
Periodical cicadas in the genus Magicicada have seven different species – all found in Illinois. They are either on a 13- or a 17-year clock and emerge earlier in the year than the annual dog day cicadas.
Which broods will emerge, where will they emerge, and when?
We can start to see periodical cicadas emerging in mid-May in Central Illinois. The first evidence of their emergence is the appearance of holes around the bases of trees. Some of the cicadas will shed and abandon their molts on branches and tree trunks.
Illinois is home to five broods, each with its own geographical distribution within the state. People in Chicago might remember the 2007 emergence of the 17-year Brood XIII. This brood extends beyond Northern Illinois into eastern Iowa, the southern edge of Wisconsin, and in a sliver of land along Lake Michigan into Indiana and, potentially, Michigan.
Brood XIX, also known as the “Great Southern Brood,” will cover the southern half of Illinois and has a much wider geographic distribution – with records in 15 states. From Illinois and Iowa, this brood can occur as far south as Louisiana and then stretch to the east coast in states like Virginia and North Carolina.
Adult cicadas will be active until mid- to late June, but you will see evidence long after they are gone, including their wings, molts, and decomposing bodies.
How do the species differ from one another in their life history and other traits?
There are seven species of periodical cicadas and they are separated either into the 13- or the 17-year broods. Generally, 17-year cicadas have a more northern distribution while the 13-year cicadas are more southerly.
There are three species within the 17-year cicadas: Magicicada cassinii, also known as Cassin's cicada; M. septendecim, the Pharoah cicada; and M. septendecula, which is rarer. The males of each species sing a different song. For example, the Pharoah cicada sounds like someone singing “Pharrrr-oah.”
[Video: Song of the Pharoah Cicada]
There are four species of 13-year cicadas. Each of the 13-year cicadas has at least one similar species within the 17-year cicadas with which they can potentially mate if they happen to emerge the same year.
Most of these species look very similar to one another, although there are slight differences in their size and coloration – an orange spot behind the eyes here, some orange stripes on the underside of the abdomen there.
Is it true that you can identify the different cicada species by sound?
Absolutely! In some cases, it is the one of the most reliable ways of telling different species apart as they look nearly identical, even to experts.
How do cicadas affect trees and other species of animals?
Cicadas are soil aerators, mature tree pruners and fertilizers. As nymphs, cicadas feed on the roots of plants in tiny chambers underground. There is little evidence that they do damage to the plant above, and if they do it is minimal.
They can damage younger trees with their egg laying or oviposition. I don’t recommend using pesticides because more cicadas will likely take the place of those you destroyed, and pesticides can harm other beneficial insects. Instead, experts recommend bagging young trees with netting to avoid damage. In uncovered trees, you'll notice “flagging,” where the tips of branches where cicadas have laid their eggs die off.
Cicadas feed a host of wild animals, including birds, fish, snakes, reptiles, insects and mammals like bears, raccoons, squirrels and foxes. Many of these animals will feast to their fullest, yet an abundance of periodical cicadas will remain to mate and lay eggs.
Finally, with the incredible amount of biomass of the cicadas, they inevitably will rot on the ground, creating an unfortunate smell but also releasing nutrients into the soil.
What do you enjoy most about studying cicadas?
When I first arrived in Illinois in August 2011, it was like stepping on an alien planet. The deafening chorus of cicadas was overwhelming. I came to learn over the years that there were multiple species calling at the same time and that different parts of the state have different soundtracks of insects singing throughout the day.
Although I love all things cicada, my primary research interests are in using genetic methods for conservation. We have several species of cicadas in Illinois that are reliant on the remaining prairies scattered across the state and they are often only found in remnants or in minimally disturbed soils, like those in cemeteries and railroad rights of way. Some of my favorite memories are trips to these tiny prairies to catch and release cicadas with my son. I hope that we can preserve these species for him and generations to come and that our landscape continues to sing. I hope that people realize that periodical cicadas and their incredible abundance are truly a natural wonder of the world – a rare and special event that we get to experience and create memories that will last a lifetime.