Landscape Ecology of Singing Insects 1: Glacial Influences

by Carl Strang

One of my winter projects has been to write new sections for my singing insects guide which go into ecological topics. This was inspired by my reading a newly published textbook on landscape ecology (With, Kimberly A. 2019. Essentials of landscape ecology. Oxford University Press, Oxford, U.K. 641 pp). In the next few posts I will share parts of the added sections. Today’s focus is the impact of the last continental glacier on the landscape and selected insect species:

Though the focus in most of this guide is on the individual species of singing insects, the field of landscape ecology provides a framework of broader patterns and questions for which the ecologically diverse singing insects provide a suitable lens.

Landscape ecology considers geographical patterns and dynamics of their change across time. Any complete biological understanding of the Chicago region must include not only what is here now but also how it got that way. Fortunately, we don’t have to go back too far geologically speaking, as our landscape is less than 20,000 years old. Three major lobes of the most recent continental glacier flowed down from the North and scoured our region’s bedrock, then began their final retreat around 18,000 years ago. As the glacier melted, with occasional periods of stalling when the push from the North was balanced by melting at the edge, it left behind a variably deep layer of various kinds of deposits. The topography was more elevated in the morainal arcs where the melt was stalled for a time, lower and flatter when the melt-back was more uniform and rapid. Occasional pocks formed where blocks of glacial ice were buried and later melted, resulting in small lakes, bogs and other wetlands. Our rivers had their start as glacial meltwater drainage streams. The Lake Michigan Lobe of the glacier picked up and crushed the softer shale from the bottom of what was to become that lake, so it left behind deposits heavy in clay west and southwest of the lake. When glacial crunching and meltwater eroded harder igneous and metamorphic rocks the ice had transported from Canada, gravel and sand resulted. Quartz sand, the most erosion-resistant component of such rocks, accumulated especially around the edge of Lake Michigan and the tributaries of the Kankakee River, which started as a glacial meltwater drainage stream originating in the part of the region covered by the glacier’s Saginaw Lobe.

This glacial history impacted our singing insect fauna in various ways. Some species require, or at least are only abundant, on sandy soils. These include the green-winged and northern dusk-singing cicadas, whose nymphs live on buried plant roots, and some of the grasshoppers, for which the sandy substrate for egg-laying and/or a poor-soil plant community is an important habitat component. A couple of species, the gray ground cricket and the seaside grasshopper, are limited to the beaches and dunes around the Lake Michigan edge.

The beaches at different points on the Lake Michigan shore have different compositions, resulting in selection for different colors in the seaside grasshopper. Here, at Illinois Beach State Park, there is a greater mix of different colors of ground igneous and metamorphic rocks.

The beaches of the Indiana Dunes are a more uniform quartz sand. Here, two seaside grasshoppers (same species as in the previous picture) would be nearly invisible if they were not flashing their inner femur colors at one another.

Kames are gravel hills formed by waterfalls within the melting glacier, and they provide a well-drained substrate. Isolated populations of sulfur-winged grasshoppers and tinkling ground crickets live on a kame in the Lulu Lake Nature Preserve in northern Walworth County, Wisconsin.

Exposed gravel on part of the kame at Lulu Lake.

All species were pushed south by the glacier, surviving in what is now the southern U.S. and being influenced by selective forces then and during the advance north as the climate moderated and plant communities spread back over the barren glacial deposits. Most of our familiar prairie and forest plant species were restricted to rather small refuges in the South during the glacial maximum, though oaks and hickories occupied a large part of the southern U.S.

Black oak savanna, Kankakee County

As the glacier melted back, open sedge tundra with some black spruce trees invaded first, then white spruces filled in to form a recognizable northern coniferous forest until around 15,000 years ago. By around 12,000 years ago most of our landscape was a mix of deciduous species, including woodlands with lots of oaks. Beginning around 10,000 years ago there was a drying period, which led to the spread of prairie through our area. The prairie then retreated as the climate became wetter, so that by 6200 years ago the western part of our region was a prairie with islands of woodlands and wetlands, grading to forest in the eastern part. This reflects a gradient of increasing moisture from west to east, mediated by the flow of wet air circulating north from the Gulf of Mexico. The drier prairies were maintained by fires which frequently knocked back woody plants that otherwise would have converted even the western part of the region into woodlands. The wooded islands within the prairie were not randomly located, but survived where rivers, other wetlands, and topographic breaks shielded certain spots from prairie fires pushed by the prevailing westerly winds. The upshot for our singing insects is a diverse landscape that to this day contains species specializing in prairie, woodland and various wetland habitats, as well as some that thrive around the edges between habitat types. A few species may be relicts of earlier changes in this history. For instance, the delicate meadow katydid, now apparently extinct in the region, is abundant in prairies to the west and probably accompanied the prairie advance. By the early 20th Century it was known in a very few scattered locations. I have not been able to find it anywhere in the present day.

Delicate meadow katydid females have longer ovipositors than their close relatives.

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.

Kankakee County

by Carl Strang

The traveling singing insect survey took me to Kankakee County one day recently. It proved to be primarily an agricultural county, and I spent much of the day finding places to which I will not need to return. The county’s gem is Kankakee River State Park, and all the singing insects I had found elsewhere in the county also were there, a total of 15 species.

An attractive scene at Kankakee River State Park.

An attractive scene at Kankakee River State Park.

These included the first robust conehead and northern dusk-singing cicadas of the year. My past experience with that cicada was occasional songs during the day, from late morning through dusk, but those in the state park lived up to their name. None sang until about 15 minutes before sunset, but then many were singing. The robust conehead was a through-the-car-window identification. It was singing in an upland meadow, and there was no place to pull off. The only other possibility for that loud droning song after dark is the false robust conehead, but until I have confirmed the presence of the latter this far north I am inclined to go with robustus. At some point I will make a series of recordings to see if I can discover the more southern of these two sibling species in our area.

Learning to Identify Insect Songs

by Carl Strang

One of the obstacles to a singing insect monitoring program is the large number of various songs that need to be learned for identification. This is not really much different from learning bird songs for breeding bird monitoring, however (except that the total number of species is smaller here). Instead of being daunted by the entire process, it is possible to take the learning process in stages, beginning with the songs that are common and easy to recognize, the ones you have been hearing all along but simply didn’t have the species labels. Here is a list of a dozen suggested species to start with in the first stage: spring field cricket/fall field cricket (their songs are identical), Allard’s and striped ground crickets, snowy tree cricket, common true katydid, black-legged meadow katydid, greater angle-wing, round-tipped conehead, dog day cicada, scissor-grinder cicada, and Linne’s cicada (for more information on these species, try the tags at the head of this post).

Snowy tree cricket, one of the species on the starter list

This list and those that will follow are for northeastern Illinois and northwestern Indiana. There would be substitutions in other parts of the country (I encourage readers elsewhere to make comments here with their own suggestions). Go to reference recordings of these species’ songs, either on-line at the Singing Insects of North America website or through the CD that accompanies the Songs of Insects book. It is not too late this year to hear many of the species on this list on the warmer days, though some are finished or nearly so.

My recommended species list to focus on in the second stage of learning consists of 8 species and groups of species: greenstriped grasshopper, gladiator meadow katydid, Roesel’s katydid ( three species that sing relatively early in the season), and then later, Carolina ground cricket, Say’s trig, sword-bearing conehead, two-spotted/narrow-winged tree crickets (no need to worry yet about separating the two), and the meadow tree cricket group (3-4 species whose songs are essentially identical to the ear and will remain so).

Roesel’s katydid is a species from the second-stage list.

This list of common species either will take you to additional, though still readily available, habitats, or else require a little more of a practiced ear (which practice you got with the first species group). In particular, seek out and spend some time getting familiar with the songs of the Carolina ground cricket and Say’s trig. They need a little more effort to recognize in the field, but once you have them, they will be touchstones for many other species (much as robin songs are for learning bird vocalizations). If you are starting now, you might push the Carolina ground cricket to the first list, as it is one of the few species singing on the cooler days and evenings.

Once you have mastered the second list of species, you are ready for the more subtle distinctions needed to distinguish the songs in the third species list. This includes separating out the song of Linne’s cicada from similar songs by the lyric cicada, and in some areas, swamp and/or northern dusk-singing cicada.

Linne’s cicada

Also, by this point you are ready to distinguish the two-spotted tree cricket song from that of the narrow-winged tree cricket. Also, the broad-winged tree cricket should stand out now from other long-trilling species. In addition, you no doubt have noticed and begun to puzzle out other species that are more idiosyncratic in their distribution or smaller in numbers that you have encountered in your favorite places.

And that brings you to the fourth stage, learning the songs of whatever remaining species may live in the area you wish to monitor. For this you will need a regional guide. In the Chicago region, you can meet this need with the guide I am developing. It is available for free as a .pdf e-mail attachment. Simply request it at my work e-mail address:

As you are learning and listening, pay attention to which songs you can hear clearly, and at what distances, and which are marginal. This will inform the limitations you will need to address or acknowledge in your monitoring.


by Carl Strang

The Tibicen or annual cicadas are a late summer phenomenon whose loud songs characterize the August days. Occasionally you may find a shed nymphal shell or a dead adult on the ground, but generally they sing out of sight, high in the trees. Last week at Mayslake Forest Preserve I had a rare opportunity to watch one in action.

This was a scissor-grinder cicada, singing only 10 feet up in a crab. The bright white underside perhaps explains its species name, pruinosa.

The cicada was walking around in the branches, singing at frequent intervals. In this photo it apparently is feeding, as its beak is extended.

The cicada was alert and watchful. As I moved within 15 feet for a closer photo the insect abruptly stopped in mid-song and was gone.

A few days later I found a dead one on the walkway near the chapel.

I have not seen a concentration of this species anywhere to match that at Mayslake. In the evening their EE-SHER-EE-SHER-EE-SHER-EE songs can drown out everything else. (Before I learned their conventional common name I used to call them lazy-dying-battery cicadas, as their song reminded me of a car engine whose battery was on its way out. This was to contrast them with the angry-dying-battery cicada, Tibicen auletes, aka northern dusk-singing cicada, whose song also is slow but has an edge to it).

Tibicen Song Sorting

by Carl Strang

My first entry into singing insects study came when I ran across the University of Michigan cicada website in 2003 or 2004. The site includes recordings of cicada songs, and as I played them I realized that all my life I had been hearing the distinguishable songs of several species without knowing it. These were all members of genus Tibicen, and that summer I recognized three common species in DuPage County.

They look very much alike, and are hard to see when singing high up in trees, so it was well that their songs were distinctive. After a couple years, however, I began to notice that the songs I attributed to one of the three, Tibicen linnei or Linne’s cicada, had two variations and with references I was able to distinguish a fourth common species, Tibicen lyricen, the lyric cicada. The differences among these species and their songs I described in some detail in a post last year.

Recently I was reviewing a wide range of singing insects reference recordings when I realized I need to pay attention again to the songs I have been identifying with Linne’s cicada. The swamp cicada, Tibicen chloromera, has a vibrato very close in speed to linnei’s. It has, however, a percussive quality in each vibration that sets it apart from linnei’s smoother, more wavelike vibrato. I had paid too close attention to written descriptions of the swamp cicada, in both the popular and scientific literature, which imply that chloromera is found only in wetlands and sings only from low perches. In fact I am now finding that at least around Culver, Indiana, chloromera often sings hundreds of yards from wetlands, and at least as often from high trees as from perches in lower ones. I have heard them in forests as well as more open stands. This is in keeping with other Tibicen cicadas, which at least in their singing perches show wide ranges in habitat.

So far I have not heard chloromera in DuPage County. I have found that I need to listen carefully, because when lyricen are singing their first, warmup songs of the day they have a slower vibrato with a percussive quality like chloromera’s.

The two areas I frequent most, DuPage County, Illinois, and Marshall County, Indiana, have different Tibicen species lists though they are only about 100 miles apart. Both are homes for canicularis, linnei, lyricen and pruinosa (the dog day, Linne’s, lyric and scissor-grinder cicadas, respectively). So far, only Marshall County appears to have chloromera, the swamp cicada, but I don’t consider the case to be closed. Marshall County also has a sixth species, Tibicen auletes, the northern dusk-singing cicada, which is associated with sandy soils and so does not occur in DuPage County’s clays.

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