Diario del proyecto 2024 Magicicada: Broods XIII and XIX

Right now in the eastern U.S., annual cicadas are singing in the trees, the last few Magicicada hatchlings are disappearing into the soil in the northern parts of Brood XIII’s range, and thousands upon thousands of holes still mark the places where nymphs surfaced during this year’s double emergence. It was a marvelous year for Magicicada, particularly here on iNaturalist.

I’m just over the halfway point (at 50.9%) of reviewing this year’s observations, but it’s already obvious that this year’s emergence has added immensely to the picture of Magicicada distribution based on iNaturalist Research Grade data. This is particularly evident with the 13-year species:

M. tredecim (before and after)
M. tredecassini (before and after)
M. tredecula (before and after)
and especially M. neotredecim (before and after)

A Kind Heart and an Iron Will
Each cicada emergence generates all sorts of interesting stories of insect/human interaction, but one of this year’s was particularly encouraging. Adrienne Lowe (@adriennefriend here on iNat) had planned a relaxing getaway from work to visit the cicadas emerging in the Lake Geneva area of Wisconsin—one of the northernmost populations of Magicicada in the U.S. When she reached Big Foot Beach State Park, she learned from conversations with park staff that people had been stripping adult and teneral cicadas from the trees and shrubs, tearing off their wings, and carrying them away by the five-gallon bucket! Although the staff were upset about this, they felt powerless to act because, somewhere along the command chain, the cicadas had been dubbed “nuisance animals” that weren’t protected under the guidelines that safeguard most wildlife in state parks.

Adrienne wasn’t willing to accept that, and immediately began reaching out to Wisconsin DNR management, local media, and cicadologists (including Gene Kritsky, which is how I became aware of the situation), making calls, sending e-mails, and gathering as much information as possible from her hotel room. (So much for the relaxing getaway!) Ultimately, Adrienne prevailed: the DNR reviewed their policy, agreed that Magicicada deserved the same protection as the rest of the park’s wildlife, and posted signs and a press release advising visitors that collecting cicadas was illegal. Her struggle was highlighted in a story by Nick Bohr of WISN 12 News, helping to get the word out about the importance of protecting the cicadas.* As a relatively isolated population on the edge of the brood’s distribution, the Lake Geneva population of Brood XIII is fragile…and hopefully, Adrienne’s efforts have helped ensure that it will be protected during its next emergence, and for future generations of cicadas (and cicada lovers).

Next Up: Brood XIV
If you’re having Magicicada withdrawal, good news: the next big emergence is right around the corner, in spring of 2025! Brood XIV, one of the most widespread broods of 17-year cicadas, has a distribution broken into several patches, the largest of which is centered on KY. Another occurs in central PA, and two smaller populations exist on Long Island and Cape Cod. The Long Island population is threatened by overdevelopment, so it will be useful to see how the cicadas have been faring since their last appearance in 2008.

Observations of Brood XIV cicadas will be collected in 2025 Magicicada: Brood XIV, which starts in only 224 days! (Don’t you love that handy built-in countdown timer?)

*At the time the story was filmed, Adrienne did not want her name released because she was still traveling in WI. She’s fine with sharing it here!

Because call pitch is such an important ID feature for the three decim species of Magicicada, I recently created an observation field, "Decim call pitch." To keep the labels short, I used mathematical symbols (specifically ≤ and >), but after using the field for a few days, I've realized that these symbols can be confusing, especially for dyslexic users. To make the field more accessible to all users, I've changed the wording to "below," "above," and "double chorus."

I've been using Raven Lite to look at spectrograms of the calls (focusing on observations in the geographic range of neotredecim) and determine call pitch. Decim call pitches appear as a solid, even, usually thin line parallel and near to the bottom of the field. I will sometimes link a spectrogram to an ID, but it's a little time-consuming, so I don't always do so: if you're really keen to see a particular one, just ask and I'll upload it (as time allows).

Dave Marshall gives a succinct explanation of the decim frequencies here:
https://www.insectsingers.com/magicicada_neotredecim_holotype/holotype.html

More and more adult Magicicada are emerging in the northern part of Brood XIX's distribution, and along with them comes the difficulty of identifying the two decim species in the brood: M. tredecim and M. neotredecim. While it's true that M. neotredecim is more closely related to septendecim and tends to be darker, variation is present in all three decim species. I've seen septendecim in previous emergences that were nearly devoid of black on the underside of the abdomen, and I've also seen surprisingly dark tredecim (in areas where only tredecim is present).

M. neotredecim is no exception; it also varies and can be a bit lighter or darker than is typical. John Cooley, who along with Dave Marshall originally described the species, noted that a population in central Illinois is atypically light: see his description of the 3D model here: https://cicadas.uconn.edu/m_neotredecim/

This is why I'm doubtful that coloration alone is a good enough feature for species ID, and why I'll continue to stick with complex-level (more accurately, species group) IDs in areas where both species are possible. As a rule of thumb, reliable genus-level records are more valuable than questionable species-level ones.

Sound recordings, on the other hand, have the potential to be very useful; high-pitched, "displaced" calls occur in areas where neotredecim and tredecim overlap. (See https://cicadas.uconn.edu/rcd/) It would be great to build a good collection of these on iNaturalist!

Temperatures are climbing, and the southeastern woods are ringing with loud cicada choruses! More observations are coming in of holes and nymphs in Brood XIII territory, so they're not far behind their southern cousins. Keep an eye out for the black patches on northern nymphs, which will appear just before they're ready to emerge and undergo their final molt.

In light of all the records coming in, I've broadened the project parameters to include "Needs ID" observations. I hope this will reduce the pressure on identifiers and relieve frustration for contributors who have submitted observations that aren't appearing in the project. It's easy to see just the RG observations by ticking one box in the filter panel, so let's welcome all Magicicada observations to the party!

Misidentifications of Magicicada are relatively uncommon, and usually consist of annual cicada skins or nymphs (which will have a broader, rounder thorax and are often greenish), CV misidentifications of species like Okanagana and Platypedia (which can typically be filtered out by range), and the occasional bee fly pupa, a.k.a. "sky shrimp" (go figure!).

As more adults emerge, remember that (at least for species ID purposes), underside photos of fully darkened adults are everything!

Spring has officially sprung, and adults have begun to emerge in the southeastern US! Three species (tredecim, tredecassini, and tredecula) have been confirmed from SC and GA, so remember to get those all-important shots of the underside of adult, fully sclerotized cicadas if you’re keen on species ID. Check out cicadas.uconn.edu/species for more info on the key characters, and to hear recordings of calls. (A few calls have already been reported on Cicada Safari!)

I’m currently traveling in northern Greece (checking in from the very pretty mountain town of Metsovo at the moment), so my apologies if I’m slow in answering questions or messages. It’s not easy to iNat from a tiny phone screen 😅