Landscape Ecology of Singing Insects 3: Changes Over Time

by Carl Strang

Some of the formalism developed by landscape ecologists clarifies the current status of our singing insects and their prospects for survival. From the standpoint of a given species, the landscape is viewed as patches of habitat imbedded within a matrix of non-habitat. If that matrix is hostile to the species, the habitat edge is a “hard boundary,” and unless the species is good at dispersing long distances, they will be confined to their habitat island. To different degrees that extreme may not be met if there are steppingstones or corridors that can act as acceptable temporary refuges for dispersing individuals. I suspect that such is the case with pine tree crickets, for example. These habitat specialists are common in conifer groves across the region, many of which seem too isolated for such a small, specialized insect to cross the intervening distances. Nancy Collins, a Wisconsin specialist on the subfamily, has noticed that pine tree cricket nymphs can live, at least temporarily, in non-conifer, herbaceous habitats. Edges of conifer groves thus are not hard boundaries for pine tree crickets. In other cases, river corridors and highway rights-of-way can serve as travel lanes. Thus, the little-known dispersal abilities of our various species are key to understanding their status.

Pine tree cricket

In some of the crickets and katydids which normally are short-winged and flightless, long-winged morphs occasionally appear. Roesel’s katydid, mentioned in the previous post, essentially is never long-winged in its native Europe, but commonly is so here, where the species is expanding its range. There is a tradeoff in play for such species. Long-winged variants are good dispersers, but their fecundity is reduced.

Roesel’s katydid, long-winged variant

Dispersal also can be facilitated by humans. I have seen examples, with Japanese burrowing crickets and jumping bush crickets, of individuals and small groups showing up far ahead of the front of their range expansion, in places where landscape materials are stored or sold.

Mate finding motivates some movement by singing insects. The females in general must travel to meet up with singing males. The males themselves also may need to change their position. In DuPage County, where swamp cicadas are relatively few and scattered, I have observed males frequently changing position between songs by tens of meters at a time. An Iowa study (Shaw, Bitzer and North 1982) found that sword-bearing coneheads shifted position an average of 6.2m between nights, but otherwise remained associated with their group of other males.

Swamp cicada

The singing insects whose habitat needs are met by landscape alterations for agriculture and residential areas are the abundant, widespread ones. They are easily picked out by the large number of sites marked on their maps in my singing insects guide. Dispersal is relatively easy for them as there are large habitat blocks well connected by amenable corridors. Even they can suffer local extinction as land is cleared of vegetation for buildings or roadways. As new vegetation grows into such places, the weedy species are quick to re-establish themselves, but this underlines the dynamism of the habitat patch mosaic.

Of greater interest, and greater concern, are those species whose needs are not met by human-created habitats. Here the habitat patches are only a small percentage of the landscape, and elements of patch size, patch isolation, and insect dispersal ability become critical to understanding. Theory suggests that when a habitat falls below 10-20% of the landscape, dispersal ability is expected to drop dramatically in the absence of viable corridors or steppingstones; such is certainly the case for many of our habitat specialists. A few species anecdotally are good dispersers. I have reports, or have seen myself, instances of slender meadow katydids and long-tailed meadow katydids showing up in locations remote from their respective habitats. These individuals were unusual among the small meadow katydids in being long-winged morphs; most cannot fly.

Slender meadow katydid

Patch isolation in some cases is such that successful dispersal is impossible. Distances among the few surviving sphagnum bogs, for example, are too great to be crossed by sphagnum ground crickets. Prairie cicadas can fly, but apparently are disinclined to do so far enough to matter. At one of their sites, the West Chicago Prairie in DuPage County, they remain confined to one area of mixed grasses and forbs. They have not crossed the 350 meters of grasses, small shrubs and wetlands that separate them from a similar area within the same preserve. So far, their populations have persisted in remnant prairies ranging from 1 to a few acres. Can such small populations survive long term?

Prairie cicada

That question raises another concept from landscape ecology: extinction debt. This is the idea that a species’ habitat may have been so reduced that it still may be present but is doomed to fade away to extinction because its numbers are inadequate to maintain reproductive viability. Such may or may not be the case for prairie cicadas. I suspect this is what happened to northern wood crickets (NWC) in the region. NWC were known from two forested areas in northern Indiana at the beginning of the 20th Century (Blatchley 1903). One of these was in Marshall County. Years ago I used the original survey notes and county soil map to reconstruct the presettlement landscape of the township in question.

Presettlement map of Union Township, Marshall County, Indiana. Mesic forest was the large green area east of Lake Maxinkuckee.

Blatchley found NWC in the area of mesic forest which, in 1834, was very large. By the end of the 19th century agricultural clearing would have been well under way, and today only a tiny portion of that forest remains, the rest having been converted to pasture and crops. The same is true of forested areas in Lake County, Indiana, the other area where NWC lived in the late 1800’s. Though fragments of the forests where Blatchley found NWC remain, the crickets are gone, and I have checked all the other relatively large forests in the region without finding them. This raises the disturbing question: how many other species presently in the Chicago region are in a state of extinction debt? Patch size needed to maintain a species is dependent upon the characteristics of the species, its population dynamics, and patch quality. These are unknowns for all the uncommon species.

Our two species are Linnaeus’s 17-year cicada, on the left, and Cassin’s 17-year cicada, on the right

I will close this section with a case study on the periodical cicadas in DuPage County. In pre-settlement times the county was, from the cicadas’ perspective, a matrix of prairies and wetlands with 18 forested areas of various sizes scattered throughout. Historical maps and aerial photos allowed me to trace changes in those forests from the early 19th Century to the present day. I measured the forest sizes, noting their smallest (bottleneck) extents and how those were reflected in the presence of periodical cicada choruses in the 2007 emergence. There was a clear threshold of local extinction: forests which had remained above 61ha (hectares) still had cicadas, those which had fallen below 52ha did not, even when they had grown larger subsequently. Old newspaper accounts placed cicadas in at least some of these. Three forests which fell between those sizes appeared to have been affected by isolation, a remote one lacking cicadas, and two near persisting populations having them. The human history peculiar to the county is important here. DuPage County is immediately west of Chicago. The western half of the county quickly became agricultural, with forests cut back to make room for fields and pastures. Forests lacking cicadas in 2007 were mainly in the west. The eastern half developed residential commuter communities, with forests being protected and expanded as people planted trees around their homes. The largest area with cicada choruses in 2007 was lobular in shape, the various lobes following the routes of commuter-serving railways and the towns that expanded along them, connecting several of the pre-settlement forest locations. When the cicada choruses reached their peak in the first half of June, numbers of the insects suddenly appeared in flight, crossing over highways and other hostile environments. Subsequently, small groups showed up in places remote from the concentration areas. Whether these will result in significant expansion of the species in the county remains to be seen, but this observation supports the notion that competition and population pressure produce responses by the cicadas. They have the advantages of stronger flight capabilities and better vision than other singing insect groups.

Landscape Ecology of Singing Insects 2: Human Influences

by Carl Strang

The previous post illustrated that the Chicago region has been a dynamically changing landscape through the recent millennia, but that now is overshadowed by the alterations our own species has made. Burgeoning human numbers have overwhelmed the planet’s ecosystems, and the native habitats described earlier mostly have been replaced by agriculture and urban growth in the Chicago region. One of the more dramatic changes is the loss of the Kankakee wetland, once described as the Everglades of the North. That vast wetland was drained for agriculture, and only a few pockets of it survive in preserves. Much of the Kankakee River in Indiana is now a straight channel with constructed high levee banks. Other smaller wetlands received similar treatment, with drainage ditches spreading across the agricultural portion of the region. This is not universally devastating to wetland species. Northern mole crickets, for instance, occasionally can be found along drainage ditches.

Drainage ditch, upper reaches of the Kankakee River, St. Joseph County, Indiana. Note farm fields on both sides.

Prairie mostly has been replaced by agricultural fields, and fire suppression has led to its invasion by woody plants. Specialists such as the prairie meadow katydid, prairie cicada and short-winged toothpick grasshopper are hard to find.

Prairie meadow katydid

My singing insects research has required a lot of driving to reach the relatively tiny surviving preserves and parks to which many of the species are now restricted. Much management effort is required in these little islands to maintain their habitats. There are exceptions, of course. Many other species have thrived under our influence. These are mainly weedy ones such as the striped ground cricket, short-winged meadow katydid and Carolina grasshopper, which do well in disturbed habitats, along with woodland edge species such as the greater angle-wing, snowy tree cricket, and jumping bush cricket, which can meet their needs in residential neighborhoods dominated by lawns and scattered trees and shrubs.

Jumping bush cricket

Habitat destruction is not the only human influence. Climate change is the probable cause of northward range expansions by several singing insect species, and it likely will lead to the extinction of the sphagnum ground cricket from the region as the sphagnum bogs dry up. Say’s cicada and some northern grasshoppers already appear to be pushed out.

Sphagnum ground cricket

Climate change isn’t simply a matter of rising temperatures, as the term “global warming” may seem to imply. Global warming is an accurate enough term, as the simplest way to measure climate change is to track the global average temperature. But the point is that our changes to the Earth’s thin skin of atmosphere are increasing its held solar energy. That energy alters patterns of atmospheric flow and the behavior of storms. Droughts, more frequent flood-causing rains, and seasonal increases or decreases in temperature that seem abnormal are examples of results we observe locally. The singing insects are forced to adjust as best they can. Droughts force sphagnum ground crickets into the wettest parts of their bogs. The severe drought of 2012 concentrated wetland meadow katydids and marsh coneheads into the small portions of the Great Marsh in the Indiana Dunes National Park that remained wet. Oblong-winged meadow katydids may be pre-adapted to such year-to-year variability. Blatchley (1920) observed that their eggs, laid in moist soil, can take 2-3 years to hatch. In my travels through the region I failed to hear a single individual in the years 2010 and 2019, but in other years they have been abundant and widespread. Some of the cicadas and other species may have similar flexibilities.

Oblong-winged katydid

People also have introduced plant species from other parts of the world which, released from the consumers and competitors which hold them in check in their native lands, have become invasive plants here. Their unfair competitive advantage has led to their displacing the region’s native vegetation in an increasing number of places. This is most evident in our wetlands. Wetland meadow katydids and other singing insects are limited to places where native wetland grasses have not been supplanted by reed canary grass, common reed, purple loosestrife, and hybrid cattails. These invasive plants are proving difficult to control, and the outlook is not good for species such as the dusky-faced meadow katydid and marsh conehead. To my knowledge the once relatively widespread stripe-faced meadow katydid now is confined to a single site, and the slender conehead, never known from many locations, apparently is gone from the region.

Stripe-faced meadow katydid

Introductions have not been limited to plants. Several species of singing insects also have been imported. Roesel’s katydid is the most common of these in our region. A European predaceous katydid, Roesel’s was introduced to the Montreal, Quebec, area several decades ago and expanded from there. They occur in open habitats with tall herbaceous vegetation throughout the Chicago region. Japanese burrowing crickets are thought to have arrived at the port of Mobile and spread out from there. They are abundant as far north as Indianapolis, and common in Rensselaer in the southern part of our region. With scattered new appearances each year occurring as far north as DuPage County in Illinois, so far, I expect them to become widespread and abundant here. The tropical house cricket represents the possibility of other, short-term introductions that are unlikely to persist in our climate.

Roesel’s katydid

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.

Closing the Book on Prairie Cicadas

by Carl Strang

The prairie cicada is a small (1-inch) insect that occurs in a few remnant prairies in northeast Illinois. Work by Dennis Nyberg and associates at the University of Illinois Chicago has revealed much of what is known about them in the state. I first gained experience with this species a few years ago at the UIC’s Woodworth Prairie in northern Cook County, then quickly discovered them in two DuPage County locations. I expected then that I would find them consistently in prairie remnants, but this has not proven to be the case.

Prairie cicada, June 2017

Recently I finished checking the last of the remnant prairies I know about in the Chicago region, and have not added any more locations to the UIC group’s 8 sites (they also listed 3 sites in downstate counties). I have not found them anywhere in the region’s Indiana or Wisconsin counties.

All the sites are small, so all the populations are small and vulnerable. Mated females do not disperse beyond their little prairie plots, as far as anyone has been able to determine. If the species is to survive in the region, the landholders (mainly forest preserve districts and railroads) will need to continue managing those sites so that the prairies can persist, and prairie cicadas with them.

Recent Travels: Singing Insects

by Carl Strang

Though my main research focus is singing insects, I don’t end up photographing them much, as I am listening for them rather than looking for them. Sulfur-winged grasshoppers continued to be an early-season focus.

Though I added several more county records for the species, there was not additional range in their color variation. This female was at Cook County’s Bluff Spring Fen.

Though I added several more county records for the species, there was not additional range in their color variation. This female was at Cook County’s Bluff Spring Fen.

Here is a typical dark male, Illinois Beach State Park.

Here is a typical dark male, Illinois Beach State Park.

Not much different, this male was around the corner of Lake Michigan at Indiana Dunes National Lakeshore.

Not much different, this male was around the corner of Lake Michigan at Indiana Dunes National Lakeshore.

Only 8 species of singing insects could be found at Goose Pond. There will be many more there later in the season.

Green-striped grasshoppers still were displaying, but their days are numbered.

Green-striped grasshoppers still were displaying, but their days are numbered.

Spring field crickets seldom come into view. This female was a challenge to photograph as she crawled among the grasses.

Spring field crickets seldom come into view. This female was a challenge to photograph as she crawled among the grasses.

This katydid nymph climbed up onto the sheet illuminated by the UV light. I am reluctant to say which conehead species she might be.

This katydid nymph climbed up onto the sheet illuminated by the UV light. I am reluctant to say which conehead species she might be.

The season seems barely begun, but already I am closing the book on two species.

The Vermont Cemetery Prairie Preserve in Will County reportedly is one of the few places in the Chicago region which still harbors prairie cicadas. They were done, however, by the time I got there on June 26.

The Vermont Cemetery Prairie Preserve in Will County reportedly is one of the few places in the Chicago region which still harbors prairie cicadas. They were done, however, by the time I got there on June 26.

I have just 3 sites to check next year as good candidates for persisting prairie cicada populations. Protean shieldbacks also apparently are done. I added only 3 county records for them in their brief 2016 season. This was a wakeup call, and I will need to get on my horse right away when they start next year.

 

Bush Cicadas

by Carl Strang

Illinois has lost nearly all the remnants of its original prairie. Thanks to the efforts of conservation agencies and private organizations you can find prairies to enjoy, but these are restoration projects for the most part. Restored prairies are nice gardens, but they lack a significant portion of the animal life. It’s a mistake to assume that “if you build it they will come.” Too many obligate prairie insects and other animals are not good dispersers. The highest priority has to be preserving the remnants, when there is a choice between devoting resources to that or to developing restorations.

A case in point is the prairie cicada, which I have featured here in the past. Another is the bush cicada. I made a trip south of the Chicago region last week to get some experience with that species, so I would know what to listen and look for in my 22-county survey area. A 2-hour drive took me to the southern fringe of Iroquois County, to the Loda Prairie State Nature Preserve.

This remnant is only 12 acres, but its quality is excellent.

This remnant is only 12 acres, but its quality is excellent.

The term “charismatic fauna” is over-used. The bush cicada is the first Illinois insect I have encountered to which I would apply that term.

For one thing, they are big and colorful.

For one thing, they are big and colorful.

They also are noisy like the other species in genus Neotibicen (formerly Tibicen, the change justified in a paper just out this year from the UConn cicada group plus an Australian researcher). I was pleased to find bush cicadas are fully as audible as our familiar Neotibicen species.

Linne’s cicada, for instance.

Linne’s cicada, for instance.

The song is like a slowed lyric cicada song, the pulse rate closer to that of Linne’s but with sharp, separate pulses. The singing was in bouts, with sometimes 10 minutes of silence between, so that the males seemed to cue their singing off of one another. They also were very active, many of the males flying to a new perch after every song. Though their flight generally was well controlled, once one bounced off the side of my head.

A male bush cicada in full song.

A male bush cicada in full song.

In the following days I sought them in several Chicago region counties, without success. The silence of those prairie remnants, some suffering from invasion by gray dogwood and other problem plants, was a sad contrast to Loda Prairie. In fairness, though, the bush cicada is primarily a southern and western species that may never have reached into the Chicago region. That won’t keep me from continuing to seek it here, though.

Prairie Cicadas Ran Late

by Carl Strang

Prairie cicadas are very locally distributed in northeastern Illinois, and I have not yet found them in Indiana or Wisconsin. Their season is brief and variable, and so I rely on a population near my home, at West Chicago Prairie Forest Preserve, to tell me when they are active each year. This year has been a bust in my search for new populations. The largest number I counted at West Chicago Prairie was only 4, on July 12, and they were difficult to pick out among the many gladiator meadow katydids, whose briefer buzz has a similar sound quality. Usually the cicadas are finished before the gladiators become numerous. There were no cicadas singing in my final check yesterday.

Side view of one of this year’s few singers.

Side view of one of this year’s few singers.

Dorsal view of the same individual. These guys are little, about an inch long.

Dorsal view of the same individual. These guys are little, about an inch long.

At least some cicada species have the ability to postpone emergence by a year. Perhaps the rain or periods of cool weather at the beginning of the usual emergence period persuaded some of these to wait. If so, there may be increased numbers next year, and I will be able to resume my search for undiscovered populations.

Not an Indicator?

by Carl Strang

Prairie cicadas are small, early-season cicadas that I first met on July 4 of last year at Woodworth Prairie in Cook County. Soon after that I found them at West Chicago Prairie and Belmont Prairie in DuPage County. Researchers at Woodworth have documenting them as emerging during a relatively brief period, mid-June to mid-July. This year I have been making weekly checks at West Chicago Prairie, and they did not appear until last Sunday, July 6.

This one sang from a bush clover stalk.

This one sang from a bush clover stalk.

That opened the door to seeking them on other sites, and I have been to two of them so far. I failed to find prairie cicadas at Horlock Hill Prairie in Kane County and at Wolf Road Prairie in Cook County. That spoils my working hypothesis that they would prove to be indicators of prairie remnants.

Here’s another West Chicago Prairie cicada, singing from a dead stem.

Here’s another West Chicago Prairie cicada, singing from a dead stem.

I hope to squeeze in a few more site checks in the next couple of weeks, but already I have the sense that this species is very limited in the locations where it occurs. I’ll also hope to get a sense of how long they are out at a given site. The July 6 appearance seems late, but this has been an odd year phenologically. So far the 11 species of singing insects have ranged from the earliest starting date in my record to nearly the latest, and the median is right in the middle. That is a little surprising given the severity and length of the winter, but first flower dates (which I hope to analyze soon) have been equally all over the place.

Sound Ideas: Prairie Cicada

by Carl Strang

Back in early July I first encountered a species I then called the short-grass prairie cicada (Okanagana balli). Its more commonly used English name has proven to be simply “prairie cicada.”

Prairie cicada. These are little guys, about an inch long.

Prairie cicada. These are little guys, about an inch long.

Here is one of the recordings of its song that I made at Woodworth Prairie:

The song doesn’t change, so you may decide not to hear all of the recording, though if you listen carefully toward the beginning you may hear a more distant individual when the recording’s main subject pauses. The song was loud enough that someone with younger ears, or me with the SongFinder pitch-reducing device, could hear it from more than 100 feet away. Unaided I needed to be within 20 feet or so.

The song is continuous, and simple, but there are so few other insects singing in late June or early July in the prairies that there is no confusion. Females clearly have no problem homing in on the singing males.

Prairie cicadas preparing to mate.

Prairie cicadas preparing to mate.

I have made a list of places in several counties where I will be seeking this species next year. I want to test the hypothesis that this is a species of prairie remnants and not of restored prairies.

Okanagana balli in DuPage County

by Carl Strang

Sunday was hot, sunny, and nearly calm, good conditions for seeking short grass prairie cicadas in DuPage County. The University of Illinois at Chicago research group had not sought them in my county, but I knew of two remnant prairies that were good possibilities. I started at the West Chicago Prairie Forest Preserve. The first short trail loop from the parking lot goes through a high quality prairie portion, and as it happened that was all I needed.

Here is one of 9 Okanagana I heard or saw at West Chicago Prairie.

Here is one of 9 Okanagana I heard or saw at West Chicago Prairie.

Having established them in one location I went on to the Belmont Prairie, a state Nature Preserve managed by the Downers Grove Park District.

Belmont Prairie is much smaller than West Chicago Prairie, but its high quality core is at least as large as the Woodworth Prairie where there is a stable population of Okanagana.

Belmont Prairie is much smaller than West Chicago Prairie, but its high quality core is at least as large as the Woodworth Prairie where there is a stable population of Okanagana.

Some clouds had come in, but the sun appeared frequently, and I heard a few cicada songs.

This one was singing from a gray dogwood adjacent to one of the trails.

This one was singing from a gray dogwood adjacent to one of the trails.

That may be as much as I will be able to do with this species this year, as the end of its brief activity period is approaching.

« Older entries

%d bloggers like this: