It is an unmistakable sound on late summer evenings with windows wide open–the hum, chirp, trill and buzz of insects. These are the night singing insects, described by Dr. Carl Strang as the cicadas, katydids, crickets and three subfamilies of grasshoppers in which males produce sound displays so females can find them and humans can hear them.
As a naturalist with the Forest Preserve District of DuPage County, IL and a little more “ear oriented than most”, Carl took an interest in the sounds of nature, including those made by insects. His curiosity led him to learn how to identify insects by sound, both by ear and by recordings using computer analysis. In 2006, he initiated a long-term general survey of singing insects in a 22-county region stretching from southeast Wisconsin, northeast Illinois, northwest Indiana and into southwest Michigan. In 2018, his annual census included a stop at MNA’s Butternut Creek Nature Sanctuary in Berrien County.
“There are about 100 species in the region and are found in every habitat except open water,” Carl explains. “They are relatively easy to survey because of the sounds, you don’t have to trap them or put in a lot of time with specialized techniques.”
“The night singers are not keystone species, most of them are not dependent on a particular plant, nor are they the main food for other animals,” he continued. “Their main value is as indicators of ecosystem quality and diversity.”
What distinguishes this group of insects, according to Carl, is that they are not big travelers, they are limited in movement, and don’t fly very far. “Singing insects can be a good indicator of the health of a system. With some animals you can build it, that is restore habitat, and they will come,” he says, “That’s not so true with singing insects.” Carl believes habitat restoration is important, but not at the expense of protecting and maintaining high quality habitat of critical sizes.
Indeed, Carl’s survey is yielding interesting results. 50 to 100 years ago, early work in the field documented species occurrences. Fast forward to current day and some that Carl expected to find or should have found, he is not finding. Some very common—like the dusky-faced meadow katydid—occurred in every marsh 50 years ago. Now he is only finding them in marshes free of invasive plants. “Only a couple of singing insects can live in that kind of habitat,” according to Carl. Habitat degradation and loss is a big factor in declines of singing insects where they once occurred.
Carl is also finding species that are in his study area now but were not here 50 years ago. Almost all these have come up from the south, he says. A warming climate may be a likely factor, although very tough to prove scientifically.
On a surprisingly cool and rainy day in August of 2018, Carl’s work took him to Butternut Creek Nature Sanctuary. There he accompanied Nancy Collins, a citizen scientist who is rapidly becoming a recognized tree cricket expert. They stopped to listen and look for the tamarack tree cricket, a species of special concern in Michigan and one that has been known to occur at the nature sanctuary. According to the Michigan Natural Features Inventory, the tamarack tree cricket inhabits dense to open tamarack swamps and fens. Carl and Nancy identified 14 singing species there—but no tamarack tree cricket.
He is not sure whether it was the cool and wet weather that day, or if they were not there at the right time of the season, or if they hit a low period in the cyclical population cycles that insects experience. “The habitat at Butternut Creek looks fine and healthy with lots of tamaracks,” Carl says. “It is definitely worth getting back in there again.”
Carl plans to stop back at Butternut Creek this summer to listen for tamarack tree crickets as he conducts his annual 22-county sweep. And starting in late July until late fall when the weather turns cold, listen for the night chorus of singing insects—and know that scientists like Carl and Nancy are listening too.