Wing Length and Song Quality

by Carl Strang

In a preliminary way I have begun to look at the question of how wing length affects song production in Roesel’s katydids. This seems pretty esoteric at first glance, but it has personal practical application, as I will explain. Roesel’s katydid is a European import which first appeared in the late 1940’s around Montreal, Quebec. They since have spread to the point that they can be found throughout northern Indiana and Illinois, and at least much of Michigan and Wisconsin. They come in a variety of wing lengths:

Short, as in this female in Kendall County, Illinois…

Short, as in this female in Kendall County, Illinois…

Intermediate, as in this male recently photographed at St. James Farm…

Intermediate, as in this male recently photographed at St. James Farm…

And long, as in this male at Blackwell Forest Preserve.

And long, as in this male at Blackwell Forest Preserve.

Researchers have noted that long-established populations in the European homeland are composed almost entirely of shorter winged, therefore flightless, individuals. The frequent observation of long-winged variations here has fostered the speculation that this has to do with dispersal as Roesel’s katydid expands its North American range. That may be true in the long run, but the edge of that range is far from the Kendall and DuPage County locations of the above individuals, and long-winged ones remain common.

Since I began my study of singing insects in 2006, I have been disappointed to find that each year my ability to hear the buzzing song of male Roesel’s diminishes. Furthermore, on hot days I can hear them fine in the cooler morning hours, but at some point I can no longer hear them. The pitch of their song rises with temperature, until it goes above my audible range. The SongFinder pitch lowering device proves they still are singing (incidentally, the buzz is steady when I hear it unaided, but through the SongFinder it has a superimposed vibrato which becomes more rapid with increasing temperature. This doesn’t happen with other singing insects).

Over the winter the question came to me whether the wing length of the males affects their song. Next year, retirement will allow time to pursue this in more detail, but for now I have an afternoon’s observations that seem to support a difference. I was following trails through north Blackwell’s meadows, occasionally listening with the SongFinder. The temperature was mid-70’s F. Many Roesel’s were singing, but I would not have known this without the device. Then I heard one unaided. I sought it out, and it was long winged. The same was true of two other individuals (the third is the one in the above photo).

Next year I want to make recordings of individuals with different wing lengths, and compare the parameters of their songs. Perhaps the analysis also will give some idea why the pitch-altered song has that vibrato. I want to think, too, about the possibility that there is an evolutionary dynamic going on here. If the song is different among males with different wing lengths, does that matter to females? If so, how? For instance, if long-winged females prefer long-winged males, and short-winged females prefer short-winged males, this could retain genes for long wings in the population for a reason other than dispersal advantage.

 

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Take Your Kids to Work Day

by Carl Strang

Last week the annual Take Your Kids to Work Day took place at Mayslake Forest Preserve. I was one of the program leaders, and I took the opportunity to test some ideas on singing insects and hearing. We tried out some insect survey methods, including sweep netting.

This was, of course, popular. You get to swing a net through the vegetation, then see what you caught.

Everyone gathered round when someone had something interesting to share.

Often there were odd little critters buried in the bits of vegetation at the bottom.

Every insect and spider got equal attention, but I was especially interested in singing insects.

One of my long term goals is to learn to identify katydid nymphs like this Conocephalus.

They also tried out the SongFinder.

This device takes in sounds and drops their pitch, dividing the frequency by 2, 3 or 4 times. Familiar sounds are made strange.

I was eager to find out how well kids could hear species I cannot hear without this device. I led them to an area where slender meadow katydids  were singing. I was mildly chagrined to learn that not only the kids heard them, but so did their younger-adult parents. I was the only one who could not. They said the song reminded them of a sprinkler.

Here they proved their ability by finding one of the singing slender meadow katydids.

This was a helpful step toward developing monitoring methods for singing insects, and everyone seemed to have a good time. By the way, I am conducting a free singing insects program at Danada this coming Saturday evening. Call 630-206-9581 to reserve a spot.

And a Child Shall Lead

by Carl Strang

One of the great benefits of teaching is that the instructor learns as much or more than the students. Yesterday I mentioned my “Wild Things” presentation on Saturday in which I shared some information on singing insects with 80 or so members of my audience. Among them were two little girls, and they, along with the questions and comments I received during my presentation, led to a brainstorm afterwards that I still am working out, but would like to share here.

One of the challenges of working with singing insects is that no one has fully worked out yet how to conduct an organized monitoring program that covers all species. The biggest single difficulty is that different people hear the insects differently. Age is a major factor. Many singing insects have very high-pitched songs, and as we age we lose the capacity to hear those high frequencies. When I have taken people into the field to listen to singing insects, we often are hearing different things, and I haven’t figured out how to get around this problem.

The short-winged meadow katydid probably is our most abundant katydid. Their songs are loud, but I cannot hear them because I have lost the ability to hear the high-pitched sound frequencies they produce.

The model that has been developed for monitoring is that individuals are trained to recognize the members of a species group, whether it be dragonflies, butterflies, frogs (by song) or breeding birds (mainly by song). The monitors then go out to an assigned area and record the species they observe.

Perhaps the way to deal with the special challenge of singing insects is to have monitoring done not by individuals but by teams, and each team must include at least one interested child.

Of course, a younger adult still able to hear all the singing insects, unaided or with a device such as the SongFinder, could do solo monitoring.

I especially like the idea that the child would be an essential and necessary team member, doing something that big grownups cannot do, making an important contribution. The adults, less distracted by the songs they cannot hear, could focus on the singers in their hearing range. That is as far as I have taken the idea so far, but I am hoping to develop it enough to explore further.

Mack Road Marsh

by Carl Strang

My second stop in my targeted search for singing insects was Blackwell Forest Preserve, specifically the Mack Road Marsh in south Blackwell. This is where the Blackwell Canada goose roost is located in winter, though no geese were there on the afternoon of this visit. As I followed the trail that skirts the edge of the marsh I heard plenty of common species (black-legged meadow katydids, Say’s trigs, Carolina ground crickets, and a narrow-winged tree cricket), and also saw some short-winged and slender meadow katydids. There were enough small willows and other coarse plants that I had few places to swing a sweep net. One sample at the edge of the water caught a couple black-leg males and this female Orchelimum (large meadow katydid genus).

She appears to be one instar short of adulthood. Her ovipositor shape to my eye could place her in one of several species, and she has the simple green and black color pattern typical of nymphs in both of our genera of meadow katydids. The photo is worth keeping for future reference, but otherwise she is unidentified, for now. As I headed back out that trail I put on the SongFinder. When black-legs are around, their songs can overwhelm the hearing, and the SongFinder’s filters don’t take them out. At one point I heard a new song pattern, however, coming from an area where grasses and some mountain mint were growing amid willow wands and some sawtooth sunflowers.

After some searching I found one of the singers, but could not get a good photo of his cerci.

As he was almost certainly a new species for my county list, I collected him. To my surprise he proved to be a long-spurred meadow katydid. Previously I had found these singing at Brookfield Zoo in Cook County, and on this most recent Labor Day weekend I was sure I had heard a couple in a woods near Culver, Indiana, that I passed on a bike ride. Those experiences led me to think this species’ songs always were audible to me. Here at Blackwell, however, though I could hear them faintly without the SongFinder I never would have noticed them without it.

This raises two possibilities, one disturbing and one intriguing. The disturbing possibility is that my Culver identification was mistaken, and my hearing has declined significantly in the past twelve months. The intriguing possibility is that these katydids alter the frequency range of their songs in different locations. At Brookfield Zoo and in those woods near Culver, there were few other singers. At Blackwell there was an abundant congener, the black-legged meadow katydid, singing in numbers. Though the songs of the two species are distinct enough that I can easily distinguish them, perhaps in these circumstances shifting to a different band width makes the male long-spurs easier for the females to find.

Slender Meadow Katydid

by Carl Strang

Last Friday at Mayslake Forest Preserve I took out the SongFinder to try and find new singing insects to add to the preserve list and to my own experience. While passing the edge of the prairie I heard a song which had the tick-and-buzz pattern of meadow katydid songs. With the device set to divide pitch frequency by a factor of four, I heard a deep rattling buzz, lasting up to 10 seconds or more but often much shorter, preceded by 3-4 fuzzy-edged ticks. I could hear the song with the SongFinder set to divide pitch frequency in half, but it was faint and very high pitched to my ear.

I selected the closest of the three individuals I could hear, and began looking for it. This is possible, given the feature of two tiny microphones, one attached to each earphone, but it takes practice. Also, I didn’t know exactly what I was looking for. Eventually I found a small meadow katydid, but the wings didn’t seem to be vibrating. Whenever it changed position under my scrutiny the song stopped, however, and I concluded that this was the singer. After flushing and having to re-find it a few times, I finally got a photo.

A more straight-on lateral view would reveal that the wings protrude well beyond the tip of the abdomen. It proved to be a slender meadow katydid, a species I had seen before but never had heard singing. I learned a few things about it while stalking it. It clearly preferred singing perches on the stems of goldenrods, despite choices of many plants with other structural features. I had gone more than 50m before encountering this little group, and will be interested in seeing if such clustering is typical of that species in our area.

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.

Gadget 2

by Carl Strang

In an earlier post I wrote about how the soprano recorder, a musical instrument, has been helpful in my singing insects research. This summer I acquired another gadget and began exploring its potential.

SongFinder b

This is the SongFinder. Microphones on each earpiece take in sounds, the electronic box alters them by reducing their pitch, and sends the results back to the earpieces. You can slow sound frequencies by one-half, one-third or one-fourth. You also can set threshold sound frequencies below which the device does no alteration. At several hundred dollars, this is not an impulse buy. I waited a couple years until I had made a good start on the insect songs I could hear unaided. But now I am at the point where I want to begin surveying additional species, mainly small meadow katydids in the genus Conocephalus, whose songs are too high-pitched for me to hear without help.

Short-winged meadow katydid 2b

This is a short-winged meadow katydid. I never had heard its song until I used the SongFinder. The song has the typical meadow katydid tick-and-buzz pattern. In this case the song is very brief, lasting one to two seconds depending on temperature. The songs repeat continuously with no gap between them. The buzz has an exceptionally rattling quality, and the 2-3 ticks are very fast. At Mayslake Forest Preserve on a recent day I heard dozens of short-winged meadow katydids whose songs vanished from my hearing when I turned off the SongFinder. Thanks to the stereo design, I found I can locate the direction from which an altered sound is coming and trace it to the singer.

I have done my best to protect my hearing. I avoid louder music concerts, and use ear plugs when necessary, for instance in 2007 when, at their peak, periodical cicadas at mid-day were chorusing so loudly that my ears hurt without protection. Even with these precautions, age gradually has eroded the upper range of pitches I can hear. The SongFinder was created for birders and other natural history enthusiasts for whom sounds are an essential part of our aesthetic.

Slender meadow katydid female b

As I continue to make use of this device in future years I look forward to hearing additional species, such as the slender meadow katydid (though not the individual in the picture, which is a female).

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