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

Shaking Out the Photo Bag

by Carl Strang

Before I get going on a new series of posts, I want to share a few photos that didn’t fit into last year’s topics.

This seemed to be a good year for gray treefrogs across the region. I frequently ran into small ones.

Gray treefrogs can change colors, making themselves green to blend in.

For some reason, they often rested on milkweed leaves.

It was a good year of singing insect field work. Plenty of questions remain unanswered.

One of the smaller ones was the identity of this grasshopper nymph at the Indiana Kankakee Sands. My best guess is sprinkled grasshopper, which I found there in adult form later in the season.

An interesting observation in the Tefft Savanna Nature Preserve (within Indiana’s Jasper-Pulaski Fish & Wildlife Area) was that short-winged green grasshoppers (Dichromorpha viridis) were the usual green color in wetlands but were brown in the savannas.

A mating pair of brown variants.

Late in the season I visited my friends Lisa Rainsong and Wendy Partridge, who live in the Cleveland suburbs. One goal was to see jumping bush crickets out in the foliage and branches of trees and shrubs. In the Chicago region they almost always stick to the trunks of trees and are difficult to see.

Sure enough, within a few minutes of searching I found a singing male in a bush.

They have an odd angular appearance, as though roughly carved from wood.

That’s it for now. Soon I will share results of a productive winter project.

More Range Jumps

by Carl Strang

One recurring theme of my singing insects survey work is the northward extension of species’ ranges. Late in this year’s field season, three more species turned up significantly north of where I had found them before. One of these discoveries was made by Nancy Collins, who found broad-winged tree crickets (Oecanthus latipennis) half a county north of the Illinois border in Kenosha County, Wisconsin, more than 30 miles beyond where I had found them before.

Broad-winged tree cricket

I had not found this species in the northernmost row of Illinois counties, but I hadn’t looked for them there in recent years. Inspired by Nancy’s discovery, I did some searching and found them in Lake County at Chain O’Lakes State Park. Next year I want to seek them in McHenry County, Illinois, and Walworth and Racine Counties, Wisconsin (unless, of course, Nancy finds them there first).

The handsome trig (Phyllopalpus pulchellus) surprised me last year by turning up in sites across the southern half of my home county of DuPage in Illinois.

Handsome trig

I set the modest goal this year of seeking them in Kane County, just west of DuPage. Recently I succeeded in that, finding a group of them a little west of where I had found them in DuPage, but that was not surprising. What bowled me over was finding a small population of them in the East Main Street Prairie park in Cary. This is 22 miles, more than half a county, farther north, McHenry County being just north of Kane. This continued the pattern of handsome trigs popping up in separate scattered locations, because I tried to find them in northern Kane County and western Lake County, areas not far from Cary, without success.

The third species is one I have written about several times before, because it is spreading quickly, and soon becomes abundant in areas behind the front of its expansion. This is the jumping bush cricket (Orocharis saltator).

Jumping bush cricket

Last year I encountered a small population of jumping bush crickets in Wauconda, Lake County, Illinois. This was a good 12 miles north of where I had found them before. I still suspect that these were inadvertently transported there by people, and I wondered if they could reproduce successfully. Indeed there were even more males singing in that spot this year. The surprise was finding them in towns all along the west bank of the Fox River, nearly to the northern border of Kane County. This is a few miles south of Wauconda’s latitude, but a search of the southeastern corner of McHenry County, between the two locations, failed to turn them up. To be continued in future years…

Jumping North

by Carl Strang

Of the many species of singing insects that have expanded their ranges northward in the past half century, the jumping bush cricket (Orocharis saltator) has been the fastest mover in the Chicago region. I have done my best to keep up with them ever since 2007, when I first heard their bell-like chirps in DuPage County, Illinois. As their density built dramatically in southern DuPage, the front of their advance typically shifted half a mile north each year.

Jumping bush cricket

At the same time, they were on the move to the east in Cook County. I first found them in Kane County, to the west, in 2014. The line of their advancing front has angled southwest to northeast, suggesting an Indiana source of the invasion, though last year I heard them singing just north of Peoria, well southwest of the Chicago region.

Over the past couple of years, what seemed to be a simple spread has become complicated. First, the advance apparently stalled out in the northeast corner of Cook County, just south of the Lake County border. Farther west, however, the crickets’ expansion has, if anything, accelerated. Following the Fox River, they have moved 8 miles up its east bank in 3 years.

But that’s not all. This year I found them even farther north on the west bank. Then, on September 20, I heard jumping bush crickets singing at the edge of Wauconda, in western Lake County. Subsequent checking revealed that this is an isolated small group, probably a human-assisted introduction. I will be interested in seeing if they successfully reproduce there. In any case, there is no end in sight to the dramatic northward movement of this species, and I will continue to invest some time each year in documenting it.

Map of the Chicago region, showing locations for jumping bush crickets. Black dots indicate counties where the species has become established. Stars indicate farthest north locations: red for 2014, yellow for 2015, green for 2016, and the two blue stars indicate new north locations in 2017, along the west bank of the Fox River in Kane County, and at Wauconda in Lake County.

Ecoblitz Continued

by Carl Strang

The Indiana Forest Alliance, a non-profit conservation organization, has been sponsoring a species survey in portions of two state forests in southern Indiana. As it consists of repeated weekend sessions over a period of years, they are calling it an “ecoblitz” rather than a bioblitz, which is a one-time event limited to a 24- or 48-hour time span. I went down for a weekend last fall, and returned in early August to complete the singing insects portion of the survey.

The area is forested, except for some small areas of tall, dense herbaceous growth in stream bottoms. The singing insect fauna consequently is mainly of forest species.

Confused ground crickets were common on the forest floor.

Confused ground crickets were common on the forest floor.

Say’s trigs by the hundreds sang in the open herbaceous areas.

Say’s trigs by the hundreds sang in the open herbaceous areas.

Widely scattered small groups of rattler round-winged katydids could be heard at night.

Widely scattered small groups of rattler round-winged katydids could be heard at night.

This nymph is recognizable as a male fork-tailed bush katydid by the distinctive appendages at the tip of his abdomen.

This nymph is recognizable as a male fork-tailed bush katydid by the distinctive appendages at the tip of his abdomen.

Some of the other species that sang for us were swamp cicadas, Nebraska coneheads, lesser angle-wing katydids, jumping bush crickets and common true katydids.

I also helped with photography at a night-time moth survey at illuminated sheets.

This small-eyed sphinx was one of the two hummingbird moths we attracted.

This small-eyed sphinx was one of the two hummingbird moths we attracted.

A blinded sphinx also dropped in.

A blinded sphinx also dropped in.

A grape leaffolder

A grape leaffolder

This lesser grapevine looper appears to be sending out pheromone.

This lesser grapevine looper appears to be sending out pheromone.

A Cope’s gray treefrog hopped in, possibly sensing the smorgasbord we had created.

A Cope’s gray treefrog hopped in, possibly sensing the smorgasbord we had created.

 

Christmas, North Carolina

by Carl Strang

My brother Gary and his wife Lisa have moved from the Eastern Shore of Maryland down to coastal North Carolina, and I joined them there for the week around Christmas. Most of our time went into unpacking and some yard work, but there were plenty of moments to explore the surroundings.

One corner of their property extends into a swamp complete with bald cypress “knees.”

One corner of their property extends into a swamp complete with bald cypress “knees.”

Some of the trees also have the iconic southern epiphyte, Spanish moss.

The most charming critter award went to the anoles that climbed the walls, shrubs and yard furniture.

It’s easy to project lots of personality into these little lizards.

It’s easy to project lots of personality into these little lizards.

Most were wearing their basic brown.

Most were wearing their basic brown.

A few switched to green, demonstrating why some call them “chameleons.”

A few switched to green, demonstrating why some call them “chameleons.”

There still were several species of singing insects performing in the unseasonably warm temperatures of those days. I recognized Carolina ground crickets, southern ground crickets (song identical to that of the striped ground cricket of the North), pine tree crickets, and abundant jumping bush crickets. I was left with a mystery, two individuals of a fifth species that sang from lawns after dark. Here is a recording:

Most of the time the spacing between trills was more evenly rhythmic than in this recording.

The recording was made well out in the lawn in front of Gary’s house.

The recording was made well out in the lawn in front of Gary’s house.

I was able to locate the presumed cricket’s position within a few square inches, but unsuccessful in seeing him. He must have been well concealed in a soil crack or tunnel. At first I thought, from the sound and the habitat, that he must be a ground cricket, but his song was louder than most ground crickets and I have never encountered a ground cricket that sings only after dark. A quick review of ground cricket recordings, and those of other likely cricket groups, in the Singing Insects of North America website, failed to turn up a match. If anyone recognizes this, I would appreciate the tip, but it was great to leave North Carolina with a mystery in hand.

 

Jumping Bush Crickets 2015

by Carl Strang

Of the many species of singing insects that have shifted their range boundaries significantly northward in the last half-century, the one that is continuing to move most rapidly is the jumping bush cricket.

Jumping bush cricket

Jumping bush cricket

In recent years I have been tracing the northernmost locations where I am hearing the distinctive songs of this cricket in northeast Illinois.

Chicago region map of jumping bush cricket locations. Black dots mark counties where I have found the species to date. Red stars indicate specific locations where I found northernmost crickets singing in 2014. Yellow stars mark places farther north where I heard them in 2015.

Chicago region map of jumping bush cricket locations. Black dots mark counties where I have found the species to date. Red stars indicate specific locations where I found northernmost crickets singing in 2014. Yellow stars mark places farther north where I heard them in 2015.

The line marking the front of this expansion is diagonal, southwest to northeast, an orientation that seems to point back toward Indiana as the source of this spread. In the central part of the line I found no indication of an advance from 2014 to 2015, but elsewhere there was a shift of about half a mile. If at some point the movement stalls out, I would expect the west end of the line to catch up with the east end and even up latitudinally, unless there is a Lake Michigan climatic influence.

Morgan Monroe-Yellowwood Ecoblitz

by Carl Strang

The Indiana Forest Alliance is sponsoring a multi-year species survey of the back country portion of the conjoined Morgan Monroe and Yellowwood State Forests in Monroe and Brown Counties of southern Indiana. They are holding bioblitz weekends at various seasons so as to get a more complete picture than a single bioblitz would produce. Jeff and Mary Stant are providing the principal organizational and logistical support. I paid my first visit on September 12 to begin inventorying the singing insect species.

While waiting my turn to go into the survey area, I checked out the base camp in an old field with scattered young trees adjacent to the riparian edge of a wooded stream. The species mix was much like I would expect to find in a dry area in northern Indiana or Illinois.

Woodland meadow katydids were very common in woodland edges, much more abundant than I have found them farther north.

Woodland meadow katydids were very common in woodland edges, much more abundant than I have found them farther north.

The old field held scattered common meadow katydids.

The old field held scattered common meadow katydids.

Handsome trigs also were common in the riparian edge.

Handsome trigs also were common in the riparian edge.

Allard’s ground crickets were one of several species at the camp.

Allard’s ground crickets were one of several species at the camp.

The forested survey area was, as expected, less diverse, though the cool afternoon temperature probably inhibited some species. The slopes held scattered confused ground crickets, and bottomland herbaceous thickets were full of Say’s trigs, along with good numbers of Carolina ground crickets and more scattered jumping bush crickets and narrow-winged tree crickets.

At one point we flushed out a medium-sized cricket which permitted a quick photo but evaded capture. It was one of the camel crickets, probably in genus Ceuthophilus.

At one point we flushed out a medium-sized cricket which permitted a quick photo but evaded capture. It was one of the camel crickets, probably in genus Ceuthophilus.

We went up to a ridge top in the evening. It was very cold, and few species were managing to sing. There were scattered tinkling ground crickets, Carolina ground crickets, jumping bush crickets, and a few feebly ticking long-spurred meadow katydids. A background hum came from the forest canopy, and occasional individuals could be distinguished to support an identification of Davis’s tree crickets, by far the most abundant singers on that cold night.

I look forward to returning for more ecoblitz weekends next year.

 

Jumping Bush Cricket Advances

by Carl Strang

The jumping bush cricket is the singing insect species that is shifting its range boundary most rapidly to the north in the Chicago region.

Jumping bush cricket

Jumping bush cricket

This one is worth following annually, and a couple weeks ago I made a few evening drives to find how far they have advanced this year.

Here is the resulting map, on the scale of the 22-county area I am surveying for singing insects. Black dots represent counties in which I have found the species as of last year. Red stars mark the northern extent in 2013, yellow ones 2014.

Here is the resulting map, on the scale of the 22-county area I am surveying for singing insects. Black dots represent counties in which I have found the species as of last year. Red stars mark the northern extent in 2013, yellow ones 2014.

The four yellow stars are in four stream corridors that the crickets sometimes follow. I did not do this check along the West Branch of the DuPage River last year. As you can see, there was a measurable hop north. For the first time I found them in Kane County; they were just south of there in Kendall last year. Also, now they have extended into northern Cook County both along Salt Creek and the Des Plaines River. These new locations represent about a half-mile northward shift, and I will be interested in finding whether they maintain that rate next year.

 

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