by Carl Strang
There is a part of me that likes to keep things simple. There is another part that loves diversity and complexity. Today’s story touches on both those aspects, and features two species, the variegated ground cricket and the Cuban ground cricket. Variegated ground crickets are not well represented in the scientific literature, I think because they seldom come out of their refuges in the soil and have unobtrusive songs. Once I gained experience with them at Mayslake Forest Preserve a few years ago in a happy accident, I began to find them elsewhere, ultimately in every one of the 22 counties in my survey area.
The mix of colors and patterns on the head, in particular, give the variegated ground cricket its name.
At roughly the same time, Lisa Rainsong found Cuban ground crickets in the Cleveland area, far north of their previously known range. They are better studied in general, because they are inclined to wander on the surface of the ground. Both of these species are in the same genus, and both have similar songs, long trills that emerge from crescendo starts. Lisa came out to my area in 2014 and made recordings that seemed to establish that variegated ground crickets but not Cuban ground crickets indeed were what I had been finding. That satisfied my simplicity loving side.
Then came September 15 of this year. I was walking the upper trail at Gar Creek Forest Preserve, just south of Kankakee and near the southern edge of my survey region, in a shaded wooded spot adjacent to a ditch in which water was flowing. I noticed a tiny cricket crawling across the trail. Thinking this might be a rare opportunity to photograph a variegated ground cricket out in the open, I got down low and took a series of photos. This was not a variegated ground cricket.
The male was largely black.
His head was black, the palps white with black end segments.
The only songs I was hearing nearby belonged to tinkling ground crickets and what I would have called variegated ground crickets. I made a recording of one of the latter, and farther down the trail toward the Kankakee River recorded another. The two recordings contrasted, the first with a dominant frequency of 8.06 kHz and 53 pulses per second, the second with a higher pitch and lower pulse rate, 8.6 kHz and 38 p/s respectively. The latter fits variegated ground cricket well. The former has the pulse rate of a Cuban ground cricket but the frequency is higher than the 7.0-7.5 range that is typical for that species.
I returned on September 26. It was a very windy afternoon, so singers were difficult to locate and isolate, but I was able to made recordings in the area where I found the suspect cricket. Again there seemed to be two categories of songs, lower pitch with higher pulse rate on the one hand (7.9/52, 7.5/signal not strong enough to read pulse rate), higher pitch plus lower pulse rate on the other (8.2/35, 8.2/34, 8.4/signal not strong enough to read pulse rate).
I found another male wandering on the trail, caught him, chilled him, and took photos against a backdrop for measurement, and upside down to check tibal spurs. The body length of 8mm and what appeared to be uneven tibial spurs seem to confirm that this ground cricket is in genus Neonemobius.
The tibial spurs are the short ones in the center of the photo; the lower one looks longer than the upper one.
The only black members of the genus in the eastern U.S. are the sphagnum ground cricket and Cuban ground cricket. Only the Cuban fits this habitat.
I did not have a collecting permit for that site, so I had to release the cricket. Next year I hope to have a permit which will allow me to take one of these crickets home for sound recordings and, ultimately, to provide a voucher specimen which may be a first record of Cuban ground cricket for the state of Illinois if I am right in my identification.
So the story has become more complicated, which satisfies my diversity loving side.