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.

Latitudinal Gradient

by Carl Strang

One of the classical challenges of community ecology is the latitudinal gradient of species diversity, species counts diminishing from the tropics to the poles. The observation is easy to make and applies across practically the entire range of species groups. Many theories have been proposed to account for this pattern, and probably some combination of factors is at play. It never had occurred to me to see whether the gradient applies across the relatively narrow latitude range of my Chicago region survey area for singing insects.

One addition to the next edition of my regional species guide will be an expanded introductory section on range extensions, along with new sections on landscape ecology and community ecology. As I drafted that material, it occurred to me that I might check for latitudinal changes in species counts.

It turns out that the pattern appears in the region’s 6 rows of counties. From south to north, median species numbers are 60, 60.5, 57, 53, 44.5 and 43.

Updated Singing Insects Guide

by Carl Strang

The 2020 version of my guide to the Singing Insects of the Chicago Region is out now.

There continue to be significant changes each year, the biggest one this time being the replacement of county maps with site maps for each species. As presented in previous blog posts, other changes include expanded information on Cuban and variegated ground crickets, nimble meadow katydids, and the addition of a page for the tropical house cricket.

The guide is available for free as a condensed 5.5mb pdf document. If you are not already on the mailing list, send an e-mail with your request to me at wildlifer@aol.com

A Tale of Two Crickets

by Carl Strang

Most of my field work in the peak month of the singing insects season this year went into pursuing nimble meadow katydids, as described in the previous post, plus going for clarity with two tiny ground crickets. Previously I had learned how to distinguish the songs of Cuban ground crickets and variegated ground crickets, close relatives whose high-pitched trills have weak crescendo beginnings and abrupt endings. That identification requires analysis of recordings in the computer.

Each point represents a different individual’s song. Variegated ground cricket songs (left-hand cluster of points) have slower pulse rates (wing vibration rates) and are higher pitched at a given temperature than the songs of Cuban ground crickets (right-hand cluster).

I knew that both species were widely distributed in the Chicago region, but wanted a more complete picture, so I visited sites in most of the 22 counties in August and September. I made recordings and occasionally succeeded in flushing out crickets for visual identifications.

Variegated ground crickets are smaller than nearly all other ground cricket species, are gray-brown with black lower faces and black backs of their heads.

Cuban ground crickets are slightly smaller than variegated ground crickets and are all black except for their black-tipped white palps.

Cuban ground crickets previously were known only as a southern species until Lisa Rainsong found them in Cleveland and then I found them in the Chicago region. They proved easy to find in all 22 counties.

Map of the Chicago region showing sites where I have found Cuban ground crickets to date.

Variegated ground crickets turned up in every county except Berrien in Michigan, though I had a relatively hard time finding them in the other eastern counties of St. Joseph and Fulton.

Map of sites where I have found variegated ground crickets so far.

Along the way I noted habitat features. Though each species has distinct preferences, there is too much overlap to allow identification on that basis. Cuban ground crickets like open grassy areas such as meadows and prairies. Dry to mesic locations favor them, though on rare occasions I found them in wet habitats. Variegated ground crickets prefer shade, and are more likely to occur where the soil is moist or there are rocks, gravel or patches of bare soil.

Otherwise the only new observation was that Cuban ground cricket songs tended to be shorter, averaging 11.1 seconds to the variegated’s 21.9. The longest Cuban trill was 25.5 seconds, and 30 percent of variegated ground cricket songs were longer than that, up to 104 seconds.

I have a good handle on these two species, I believe, and will be able to concentrate on others in next year’s peak season.

Kayaking for Katydids

by Carl Strang

One of my top goals for the field season just past was to seek out nimble meadow katydids in Wisconsin and Indiana. That called for a lot of kayak trips, as the nimble meadow katydid lives on emergent aquatic plants in relatively deep water. Sometimes you can hear them singing from shore, as at parks on the Grand Mere Lakes in Berrien County, Michigan, where I found them under way on August 10.

Nimble meadow katydid, Orchelimum volantum

On the 14th I headed to Indiana, where a few lakes remained to be checked. I had not found the species in that state in lakes where it had lived in the early 20th Century plus others that seemed like good possibilities. I paddled into the Twin Lakes in Marshall County and found a few nimble meadow katydids singing along the channel separating the lakes. They were persisting on some aquatic knotweed plants growing among the dominant purple loosestrife, an invasive semishrub that supports no native wildlife. No luck at Pleasant Lake in St. Joseph County, but at the final stop of the day I found a substantial population of the katydids scattered around the two lobes of Fish Lake in LaPorte County.

Camp Lake in Kenosha County, Wisconsin, had habitat that looked good for nimble meadow katydids.

Beginning on August 17 I made a few trips into southern Wisconsin. Nimble meadow katydids never had been observed in that state, but I had found a small population at Illinois Beach State Park just south of the Wisconsin border. Camp Lake, showed above, looked promising, but harbored none of the katydids. I went on to check 15 more lakes in southern Kenosha and Walworth Counties, but had to conclude that there are no nimble katydids to be found in Wisconsin.

I have a few more places to check in Illinois, Indiana and Michigan, but the picture is clear that the nimble meadow katydid occurs in just a few widely scattered populations in the Chicago region.

New Sites

by Carl Strang

I enjoy going back to places I have visited before as I survey the singing insects of the Chicago region. Some are beautiful, some have the possibility of harboring species I haven’t found there yet. I am finding, however, that the greatest jumps in progress come from visiting new places. Today I wish to mention some of the ones I checked for the first time this year.

Stoutsburg Savanna Nature Preserve

The Stoutsburg Savanna is a state nature preserve in northern Jasper County, Indiana. I realized that I had done nearly all my Jasper County survey work in the Jasper-Pulaski Fish and Wildlife Area, and I needed to look elsewhere. Stoutsburg’s beauty was a pleasant surprise, and I made some nice observations there.

Mottled sand grasshopper, Stoutsburg Savanna

Another new Jasper County site was the combined NIPSCO Savanna and Aukiki Wetlands. Though much of the latter, sadly, has been taken over by reed canary grass and other invasive plants, part of the area remains good quality.

The prairie portion of the site had handsome grasshoppers.

An Aukiki broad-winged bush katydid

I was glad for the opportunity to get a series of photos of this female broad-winged bush katydid.

Another site I had been wanting to see was Wintergreen Woods Nature Preserve, a LaPorte County (Indiana) Conservation Trust property. This was another pleasant place to visit.

Wintergreen Woods provided me with a county record for the clipped-wing grasshopper, a crepitating species.

The best observation at a new site came from the Ruth Kern Nature Preserve, an Acres Land Trust property in Fulton County, Indiana.

An interesting looking katydid peeked at me from a grass leaf.

It proved to be a marsh conehead, the first I have seen outside the Great Marsh of the Indiana Dunes National Lakeshore and Indiana Dunes State Park.

I released the female after taking a series of documenting photos.

The Ruth Kern preserve’s forested trails are pleasant to walk, looping down to the Tippecanoe River.

I look forward to new discoveries in future years at sites I still haven’t explored. It is good to see the work done by governmental and private agencies to protect some of the best wild places.

Strangers in the Neighborhood

by Carl Strang

In the late summer I started hearing a strange sound at night in my neighborhood:

There were several of these singers scattered up and down the street. Clearly they were some kind of cricket, but this was an unfamiliar sound. I confess that my first reaction was to be affronted. How dare a singing insect start doing something I didn’t recognize in my own neighborhood? I tried turning them into a familiar species, perhaps an odd courtship sound by striped ground crickets? Could there have been a chromosome doubling, altering the sound analogous to the Cope’s vs. gray treefrog? I made the above recording and looked at it in the computer.

Each of the rapid little chirps was composed of two pulses.

I was sure that nothing familiar could have produced this. I found that the sounds were coming from the seams between sidewalk concrete blocks, or around curbs. I was plotting to flush one out but had a stroke of luck. While walking to my mailbox one night, I spotted an unfamiliar cricket out on the street. This had to be one of the strangers, as it was much bigger than a ground cricket yet smaller and paler than field cricket species I knew. He was quick, but after a few missed attempts I was able to pin him against the pavement with my palm. I got him into a container and set up my white chamber for photos.

Viewed from above, the short wings, tan color, and black line across the rear edge of the pronotum stood out.

The overall shape and color pattern seemed to fit the field cricket group.

I had tried to be gentle, and hoped that the loss of his antenna tips was due to combat with a rival rather than my capture.

In the Singing Insects of North America website, it was quick work to identify him as a tropical house cricket, Gryllodes sigillatus. This is a species whose range is a narrow zone around the edge of the Gulf of Mexico and extending west. I couldn’t see any way they could have spread north from there, at least not without my having encountered them before. One of my neighbors must have transported them, possibly as an egg mass in a potted plant.

So, what are the odds that this exotic cricket should turn up in the neighborhood of a singing insect specialist? Should I feel privileged, or special, at such a cosmic coincidence? While I am not in a position to rule that out, it makes more sense to me to interpret this in a different way. It seems more likely that this sort of thing happens a lot. This and other singing insects get transported around, show up in odd places, but are not noticed because people don’t know them. And what wonders have I missed in my own ignorance of other organisms that have appeared under my nose without me noticing them?

The tropical house crickets still were singing at the beginning of October. I imagine that some mated and produced eggs. While I will listen for them next summer, I will be very surprised if any of those eggs survive our northern winter.

Footnote: As a runner myself, I followed the world track championships in Qatar at the end of September into the beginning of October. As I watched coverage of the men’s marathon, held at night because of that country’s tropical heat, I frequently heard a now-familiar sound. A quick internet search turned up the fact that the tropical house cricket is not native to the U.S. but rather to southwest Asia, and has been spread all around the tropical regions of the world.

Finds Along the Way

by Carl Strang

It has been a full and busy field season, so full that I have neglected the blog, for which I apologize. Today I begin to catch up. There will be a series of posts on this year’s singing insects research, but for now I will share a few side observations made along the way. The best of these was my first jumping mouse.

Meadow jumping mouse

This little rodent is widely distributed in the region but seldom seen. I went well into my 69th year before I finally saw this, my first one. It was smaller than they are supposed to get, so I assume it was a youngster whose naivete made it possible for me to watch him. Still, he was shy enough that the above photo was the best I could get. If you enlarge it for a better look, note the very long tail which trails off the right margin. Also, look beneath his (I say his, don’t know the gender) belly at the very large hind foot sticking out. I admired his beautiful golden coat as he hopped among the plants on those hind feet, nibbling here and there.

I fit some monitoring walks at St. James Farm into my summer. On one of them I ran across a perched wandering glider.

Wandering gliders usually are seen only in flight, distinctive in being large yellow dragonflies with chestnut brown heads.

This species has a worldwide distribution, and routinely crosses oceans. I remember seeing one in Australia.

Earlier in the season at St. James Farm I saw a queen bumble bee with a striking color pattern.

The black-and-gold bumble bee has yellow hairs on top of its head, which allow separation from the similar Bombus pensylvanicus.

Even more special was a summer sighting of a rusty-patched bumble bee.

This one is distinguished by a reddish area surrounded by yellow at the base of the abdomen.

The full pollen baskets and wild bergamot host speak to the bee’s focus that day, as well as the time of the season.

This was special, because the rusty-patched bumble bee is a federally endangered species. Fortunately, it was on protected public land, and of course I reported it to the owning agency.

A Pause in the Action

by Carl A. Strang

In the early part of the season, from April to early July, my research focus is on those species of singing insects which matured from overwintering nymphs, plus some small early-season cicadas. This is a minority of species, as most of the crickets, katydids, and singing grasshoppers mature after the middle of July, having wintered as relatively secure eggs and needing time to grow up.

I was able to close the book on northern wood crickets last month, and the story here is a sad one. This forest-dwelling member of the field cricket group had been reported from two northern Indiana sites by W.S. Blatchley in 1903. As far as I know, no one has sought them since then in the northern part of the state. Last year I determined that they no longer occur where Blatchley found them. This year I checked the largest other eight forests in the Indiana portion of my study region. If they ever were there, they are gone now. I suspect that forest fragmentation for agriculture and other purposes is responsible for the loss. Blatchley’s detailed descriptions leave no doubt that he knew how to recognize the species.

This northern wood cricket is from the northernmost site where I know they still occur, Eagle Creek Park in Indianapolis.

I was able to close the book on another southern species, the spring trig, in June.

This tiny, early-season cricket is common in southern Indiana.

I have found a few scattered groups of spring trigs in southernmost Fulton and Jasper Counties in Indiana. A thorough search failed to turn them up in neighboring Pulaski and Newton Counties. I may check again in a few years, on the possibility that the species is expanding northward.

One positive result was finding sulfur-winged grasshoppers in the East Main Street Prairie of Cary, Illinois. This adds McHenry to the counties where I have found the species. They probably occur in every county in my region but are common only on sandy or gravelly soils such as Cary’s kame-like hills. I have learned of another candidate site which may add Fulton County, Indiana, next year.

Sulfur-winged grasshoppers are characterized by bright yellow hind wings, which they rattle in flight to produce their song.

Prairie cicadas started a little late this year. I was pleased to find that management efforts to remove brush from the West Chicago Prairie Forest Preserve near my home appears to have paid off in both rebound of diverse prairie vegetation and an increase in the cicada numbers.

Prairie cicadas, are tiny, around an inch long.

Failure to perform such restoration work has a cost. Once known to occur in Kankakee County, prairie cicadas apparently are gone from there, the prairies having been degraded by brush, teasel and other invasive plants.

A final story is that of the periodical cicadas. In each cycle since 1973, the main appearance of 17-year cicadas in Chicago’s western suburbs has been preceded by a significant, 4-year-early emergence. This happened in 1969, 1986, and 2003. I suspect that in a small part of this area, all the cicadas now have switched to the early time. If you have done the math, you realize that it may happen again next year. One predictor to watch for are what I call oops cicadas, a few individuals who jump the gun by a year, or miss the main emergence and come out a year late. As expected, this has been happening this spring. I have heard 3 individuals myself in two cities and seen photos of the insects from 3 more. Counting and mapping them will be a highlight of next year’s early field season.

I predict that some areas will have good numbers of 17-year cicadas next year.

2019 Bioblitz

by Carl A. Strang

Each year the Indiana Academy of Science co-hosts a bioblitz somewhere in that state. This year’s site was The Center at Donaldson, which includes a retreat center and Ancilla College, plus surrounding properties. I always take the singing insects in this annual 24-hour count of species, but no one came to cover Lepidoptera or Odonata in 2019, so I appended them to my commitment. That is just as well, because these events are scheduled early enough in the season that few singing insects have reached the adult stage.

Some Roesel’s katydids matured in time for the bioblitz.

Two of the five singing insect species I found were common early species that were nearly finished, two were common mid-season species recently coming into song, and one of them provided an observation of significance. The eastern striped cricket is thinly scattered in northwest Indiana, possibly expanding into that region from the south or west. A single male singing in the evening provided a Marshall County record, a full county’s width farther east than I have observed them before.

I enjoyed re-acquainting myself with the beauty of dragonflies, damselflies, butterflies and moths, and photographed many of them.

The widow skimmer was the most abundant dragonfly.

Most of the eastern or common pondhawks still were green. Males will change to blue over time.

The Halloween pennant pleases the eye.

There weren’t many damselflies. Here, a blue-fronted dancer.

Newly emerged eastern forktail females are orange.

A few monarchs graced the grounds.

There were many great spangled fritillaries, plus this meadow fritillary.

I encountered a few moths during the day, but most came to my ultraviolet light setup in the forest, or the Purdue team’s assorted bright lights in the open. Moths are underappreciated for their beauty, diversity, and ecological significance.

Large lace-border, Scopula limboundata

Reversed haploa, Haploa reversa

Painted lichen moth, Hypoprepia fucosa

Delicate cycnia, Cycnia tenera

Isabella tiger moth, Pyrrharctia Isabella

Imperial moth, Eacles imperialis

Hermit sphinx, Lintneria eremitus

Snowy-shouldered acleris, Acleris nivisellana

Oblique-banded leafroller, Choristoneura rosaceana

Grape leaffolder, Desmia funeralis

Grape plume moth, Geina periscelidactylus

Large maple spanworm, Prochoerodes lineola

Lesser maple spanworm, Macaria pustularia

Small engrailed, Ectropis crepuscularia

Ovate dagger, Acronicta ovata

Pink-barred pseudostrotia, Pseudostrotia carneola

The Hebrew, Polygrammate hebraeicum

The brother, Raphia frater

Along the way I encountered a few other species to add to the species count.

Narrow-winged grasshoppers were common on the bioblitz base camp’s sandy hill.

A Pennsylvania wood cockroach came to the UV light.

The light also drew this striking summer fishfly.

 

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