Some Cicada Site Maps

by Carl Strang

Today I close this series of posts on my site mapping project. Three of our Chicago region cicadas’ maps revealed interesting patterns that raised questions for me. Let’s start with the green-winged cicada (Diceroprocta vitripennis).

Green-winged cicada

Green-winged cicada all sites map

This is a species that is limited to sand soil areas along the edge of Lake Michigan and the Kankakee River. I was a little surprised that the latter sites all were south of the river, but that could be in part because I haven’t visited many sites on the north side. Now let’s consider another sand-soil species, the northern dusk-singing cicada (Neotibicen auletes).

Northern dusk-singing cicada, museum specimen

Northern dusk-singing cicada all sites map

What strikes me here is that the northern dusk-singing cicada extends much farther into the sandy southeastern counties. I’m a bit puzzled by this, as there is habitat in southeastern Starke County and southwestern Marshall County which seems very similar to places where I have found green-winged cicadas farther west. The only possibility I have come up with so far is that the green-winged cicada is smaller and weaker, and may not be able to find mates as readily in the fringes of its range.

A final case study, and the one that intrigues me most of all, is that of the swamp cicada (Neotibicen tibicen).

Swamp cicada

Swamp cicada all sites map

There are plenty of sites with swamp cicadas in the eastern two ranks of Indiana counties plus Berrien County, Michigan. That connects them to Cleveland, where Lisa Rainsong reports this as one of the most abundant cicadas. I had not realized, until I made this map, that I have found them only adjacent to the Kankakee River farther west in Indiana, plus the Momence Wetlands site in eastern Kankakee County, Illinois. I have spent plenty of time along that river farther west and have made no further observations. But then swamp cicadas show up again as scattered individuals and small groups in DuPage County and parts of the adjacent counties. For now I have to regard this as a disjunct part of the species’ range. Perhaps a few wandering individuals occasionally provide gene flow into this isolated northwestern group, but otherwise I wonder how long it has been separate in this way.

Advertisements

1 Comment

  1. wilson said,

    May 20, 2019 at 11:23 pm

    This is your longest blog-sabbatical in several years.

    If you’re moving away from the blog, I want to take this opportunity to say thanks, I’ve enjoyed it, and I hope everything is going well for you.

    But I also hope you’ve got more interesting posts for us.


Leave a Reply to wilson Cancel reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: