Roesel’s Katydid Update

by Carl Strang

A year ago I reviewed some of the biology of Roesel’s katydid, a predaceous species native to Europe that has been introduced to North America. I described the data I had begun to collect on the expanded range of that species. Most available range maps show it in a large area of the northeast (it first was observed in Quebec, and has expanded well into the northeastern U.S. with observations as far east as northeastern Ohio). Some maps also show an isolated range area in northeastern Illinois.

A few years ago I found what none of the maps show, that Roesel’s has expanded into Indiana as well. Last year I began to explore the extent of that expansion, finding Roesel’s everywhere I looked, from Marshall County as far south as Logansport and as far east as North Manchester.

This year my own study has been put on hold, as my available time has gone into taking care of my parents. There has been progress, however, as fellow nature blogger Scott Namestik (of Through Handlens and Binoculars) has become interested in this katydid and has found it in a number of counties in northwest Indiana, connecting my Indiana locations with those in northeast Illinois.

In our correspondence we have been considering the possibility that the Indiana and even the Illinois insects may not represent an isolated introduction, but instead may have resulted from a more widespread expansion of the eastern range than anyone has realized. Though singing insects have attracted increased attention from amateur naturalists in recent years, there have been relatively few people studying them, and there is a learning curve in this study. I still have some puzzles to sort out in the identification of common species in my own DuPage County, Illinois, four years after I began to focus on singing insects fairly intensively. We are getting to the end of the Roesel’s season for this year. Nevertheless, Scott and I would be interested in any observations readers may have made of this species between Whitley County, Indiana, and the Cleveland area, or south of Cass County, Indiana, or Kendall County, Illinois. There are reports of Roesel’s in eastern Iowa, as well, which likewise is beyond any published range map I have seen.

A final note in my own observations of Roesel’s was provided by an 8-year-old girl during a nature walk I recently led at Mayslake (where I took the above photo). It became clear that she was hearing the singing Roesel’s much better than I was. She was hearing more of them than I was, she was picking up individual songs sooner than I was, and they were so loud to her ears that she complained once of the volume, when I could hear them plainly but would not have said they were loud. I have taken relatively good care of my hearing, but at 59 years I have experienced a typical loss of hearing, particularly in the high frequency range. When I tried out the SongFinder device  on Roesel’s, I found that indeed their songs are quite loud, and I was grateful again for the invention of this aid to the aging naturalist.


  1. July 15, 2010 at 8:40 pm

    Hi Carl. I added Porter County, Indiana to the known distribution of Roesel’s Katydids today, so I’ve now seen them in every county from St. Joseph, Indiana west to Illinois.

    Regarding being able to hear Roesel’s Katydids, they definitely sing at a pitch that some people simply cannot hear. I agree with the 8-year old you talked to, that they can be loud and even annoying (in driving 60 mph between work and home with the windows down, I can hear their electric short-like buzz). However, on a recent birding field trip, I began hearing them and tried to point them out to a birder who is around your age, and he could not hear them, even at point-blank range. He also is not able to hear Cedar Waxwings, Brown Creepers, or other high pitched bird songs. It has to be frustrating for him, and I hope the day never comes where I lose the high end of the range of my hearing ability.

    • natureinquiries said,

      July 18, 2010 at 8:29 pm

      A few years ago I defined my annual hearing test as the ability to hear that final high note on a blackburnian warbler’s song in spring. I continue to pass that test, but the singing insects have humbled me. I am so glad, though, that I have not gone to a lot of rock concerts!

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