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.

A Visit with OecanthiNancy

by Carl Strang

Nancy Collins fell in love with tree crickets when a male two-spotted tree cricket found his way onto one of the potted plants on her apartment balcony and began to sing. That encounter led to one of the more remarkable stories in present-day singing insects research. Nancy’s passion has led to a comprehensive web site on tree crickets, expeditions in North and Central America, and co-authorship of scientific papers describing new species.

Nancy with a netting-enclosed cluster of goldenrod tops holding some Forbes’s tree crickets. Nancy is the one on the right (small joke).

Nancy with a netting-enclosed cluster of goldenrod tops holding some Forbes’s tree crickets. Nancy is the one on the right (small joke).

Nancy now lives in rural Racine County, Wisconsin, and last week showed me the study plot she is managing for her experimental studies. Her projects include the distribution of tree cricket species in Wisconsin, identifying characteristics of the various species’ nymphal stages, and color variation among Forbes’s tree crickets. That last species ranges considerably, from largely black to quite pale, often in the same local population. Nancy is enclosing groups of tree crickets segregated by color on various host plants, and will follow their offspring next year to begin sorting out genetic and other influences on that color variation.

During that visit I was able to add a few singing insect species to my spreadsheet for Racine County.

These included the fork-tailed bush katydid.

These included the fork-tailed bush katydid.

This female marsh meadow grasshopper had an unusually beautiful color pattern, but most of the many individuals of this species had the typical coloration.

This female marsh meadow grasshopper had an unusually beautiful color pattern, but most of the many individuals of this species had the typical coloration.

The green cerci and long wings identify this male slender meadow katydid.

The green cerci and long wings identify this male slender meadow katydid.

Note: the name in the title is Nancy’s, not mine. It is her handle for Internet use, combining the family name for the tree crickets (Oecanthinae) with her own. She does not capitalize the Nancy portion, however.

 

McHenry County Visit

by Carl Strang

On September 3 I drove up to McHenry County, Illinois, to continue my regional survey of singing insects. I spent most of that hot afternoon at the Pleasant Valley Conservation Area.

This county park has some very good woodlands and savannas.

This county park has some very good woodlands and savannas.

The day produced 7 county records.

My first four-spotted tree cricket in McHenry was at Pleasant Valley.

My first four-spotted tree cricket in McHenry was at Pleasant Valley.

A shift to the Hickory Grove Conservation Area produced additional observations, some of them remarkable.

The most unexpected find was a small group of gladiator meadow katydids, still singing weeks after they normally are done.

The most unexpected find was a small group of gladiator meadow katydids, still singing weeks after they normally are done.

The photo shows the characteristic pronotum profile and cerci. The marsh habitat and the distinctive song pattern, with the ticks finishing, rather than preceding, the buzz portion of the song all were consistent with gladiator meadow katydid. The black spots on the abdomen may be signs of a parasite load; could that have delayed the completion of development?

The same site produced this marsh meadow grasshopper.

The same site produced this marsh meadow grasshopper.

The Lyons Prairie and Marsh, administered as part of Hickory Grove by the McHenry County Conservation District, actually is in Lake County. I followed the trail into a portion of the marsh dominated by reed canary grass. In addition to abundant slender and short-winged meadow katydids, I got an intriguing glimpse at a female Orchelimum that might have been a dusky-faced meadow katydid, which I have yet to find in Illinois. I was unsuccessful in getting a better look in that late afternoon, but at some point I need to get back there for a thorough search.

On the way back to the car I spotted this tiny grasshopper. Mature at around 3/8 inch long, it is a non-singing species, the black-sided pygmy grasshopper.

On the way back to the car I spotted this tiny grasshopper. Mature at around 3/8 inch long, it is a non-singing species, the black-sided pygmy grasshopper.

McHenry County Exploration

by Carl Strang

On Friday I took a vacation day to check out some sites in McHenry County for their singing insect potential. I saw parts of 4 widely scattered Conservation Areas (their equivalent of Forest Preserves), and picked up 4 county records for my study along the way.

Within minutes of arriving at the first site, Elizabeth Lake, I spotted this bush katydid feeding on a tansy flower head.

Within minutes of arriving at the first site, Elizabeth Lake, I spotted this bush katydid feeding on a tansy flower head.

The small body size, and the shape of the ovipositor, identified this female as a fork-tailed bush katydid.

The small body size, and the shape of the ovipositor, identified this female as a fork-tailed bush katydid.

That was not one of the county records, but I did pick up two at that site: Forbes’s tree cricket, and slender meadow katydid.

The area with the greatest potential proved to be Hickory Grove-Lyons. These areas are a political oddity. Though the Lyons portion is in Lake County, it is cut off by a bend of the Fox River, and so managed by the McHenry County Conservation District.

A boardwalk leads through a high quality marsh at Hickory Grove. Other marshes and woodlands in this, and the adjacent Lyons area, are priorities for future exploration.

A boardwalk leads through a high quality marsh at Hickory Grove. Other marshes and woodlands in this, and the adjacent Lyons area, are priorities for future exploration.

The year’s first Texas bush katydids, which also provided a county record, were singing in that marsh. The fourth county record, common true katydid (which seems oddly uncommon in McHenry), came at a good-looking forested preserve, Coral Woods. I look forward to return visits to some of these sites.

 

National Lakeshore Wetlands

by Carl Strang

After catching the melodious ground cricket I drove to Pinhook Bog, a part of the Indiana Dunes National Lakeshore that is open to the public only on rare occasions. I hoped to find stripe-faced meadow katydids, but the bog’s public access boardwalk was bordered by little in the way of grasses and sedges. I was gratified, however, by the presence of sphagnum ground crickets.

These were the first I have found in Indiana. I have seen them only at Volo Bog in Illinois.

After lunch I returned to the place where Gideon, Nathan and I caught the marsh coneheads in early August. Gideon had relayed the news that some of the meadow katydids Nathan also had caught there were dusky-faced, one of the conservative species I had yet to find. The lead paid off.

The legs were totally green, unlike those of the familiar black-legged meadow katydid.

I caught a couple individuals to hold for close-ups.

The head of the dusky-faced meadow katydid is amber colored, with fine dots and lines of red-brown.

While wading the tall grasses and sedges I also spotted a different large meadow katydid with green legs and a beautiful yellow-green face.

Unfortunately I only saw the one, and the auto-focus on the camera frustrated my attempts at a clear photo before she flew away. Though blurred, the image provided enough information for identification.

This was another species on my conservative wetland singing insects want list: the delicate meadow katydid. So, what was so special about this place?

View of the edge of the portion of the Great Marsh under discussion.

For one thing, invasive Phragmites was absent, and cattails were limited to a few scattered plants. Grasses and sedges were the dominant plants. Black-legged meadow katydids were very few, and limited to the dry-soil edges of the wetland. The plants and katydids were zoned. Just inland from the water and mud-flat edge was a zone of shorter, finer grasses in which the only singing insects I saw were abundant slender meadow katydids. Then came taller grasses of intermediate coarseness, where the dusky-faced and delicate meadow katydids were, along with a few marsh coneheads.

Female marsh conehead

The soil became progressively less water saturated as the vegetation rings went outward. Next came a zone of very coarse sedges. The only species I saw in there was, surprisingly, a long-tailed meadow katydid (a tiny species dwarfed by the big triangular sedge stems).  Interspersed here were patches of taller grasses which contained more dusky-faced meadow katydids. This area gave me a strong image of good marsh habitat to carry as I continue to search for these insects in other places.

Chain O’Lakes

by Carl Strang

Last week I spent a day and night at Chain O’Lakes State Park, near the Wisconsin border in Illinois. There are extensive wetlands in that park as well as dry upland areas. Though my singing insect search for the most part turned up common, expected species, I have hope for better results in a future wetter year. In the extensive upland restored prairie areas Allard’s ground crickets were the main daytime singers. In a lower, damper, goldenrod-dominated patch were some black-horned tree crickets (or, possibly, their sibling species the Forbes’s tree cricket).

The heavy but well separated basal spots on the antennae plus the dark antennal color identify this as a black-horned.

In a higher-quality prairie patch not far from some trees I found a bush katydid.

The species cannot be determined from this angle.

A quick capture made for an easy identification.

The brown, curved ovipositor distinguishes the female fork-tailed bush katydid.

Later, after dark, I heard a number of sword-bearing coneheads in the prairie areas.

This species, with its distinctive sewing-machine song, is common in meadows and prairies of the region.

Wetlands are abundant at this park, and some appear to be relatively high in quality.

Pike Marsh

The singing insects were of common species for the most part.

The slender meadow katydid is abundant in wet places.

The most conservative species I found at Chain O’Lakes was a female long-tailed meadow katydid.

This was the first green-legged female of this species I have seen. Usually they are all brown.

I will return to that park in a wetter year.

Meadow Katydid Nymphs

by Carl Strang

One project in my study of singing insects is to learn to identify nymphs, the immature stages, of katydids. This could extend the survey season, as I could begin a month or two earlier than at present. At some point, rearing and taking quantitative measurements will be necessary (unless there is some reference I have not found), but for now I am taking a lot of photos and looking for possible characteristics to watch. I am beginning at Mayslake Forest Preserve, which has relatively few species. Recently the first slender meadow katydids matured and began to sing.

Mature male slender meadow katydid. Note the long wings, green cerci at the abdomen tip, and the green femurs with lines of tiny, separated black dots.

Some of the nymphs I was catching in the sweep net looked like they, too, might be males of this species.

This nymph likewise has green cerci, though not yet in adult form, and green femurs with tiny, separated black dots.

Some of the female nymphs show the same color pattern, though they have undeveloped ovipositors rather than undeveloped cerci.

Again, a bright green general color with tiny black dots on the femurs.

In contrast, many of the nymphs show color patterns that I suspect tie them to adult short-winged meadow katydids, the other common member of genus Conocephalus at Mayslake.

Note the browner ground color, the many brown dots, the yellow-brown cerci, and especially the femur with its central clear zone bounded on each side by a brown band.

Females are similar.

Again the green is paler, and the femur shows the same striping.

Some nymphs are more ambiguous, but most seem to fall into one or the other color pattern, which is encouraging.

Stripes

by Carl Strang

Identifying species of small meadow katydids (genus Conocephalus), especially nymphs, can be challenging. Most adults are readily sorted out, especially males if you can get a good look at the cerci or claspers at the tips of their abdomens.  Females are trickier, but their ovipositors often allow distinctions to be made. I’ve decided to take a shotgun approach in my survey at Mayslake Forest Preserve, sweep sampling on a weekly basis and taking photos of as many individuals as I can. Last week I noticed something that is potentially helpful.

This is an unambiguous male short-winged meadow katydid. Cerci are right, lots of orange color around the abdomen tip, short wings, small size.

As I compared my many photos, I found that the color pattern on the sides of the hind femurs drew my eye. Notice the band of clear green color bounded by brown stripes on either side. Here’s a female, again clearly a short-winged.

Though she may be an instar short of adulthood, this one has the ovipositor of a short-winged.

Again the color pattern on the femur appears. I did an Internet search, and except for some photos from Texas, short-winged meadow katydids show this striping pattern across eastern North America. Then I began to compare other species. I started with another familiar one, the slender meadow katydid.

This male I photographed last year has clear green femurs, without the stripes.

Again an Internet and reference book search showed consistently clear green femurs on this species. However, I was surprised to find that a female I had identified a couple years ago as a slender meadow katydid had the femur stripes.

The long wings fooled me. The ovipositor actually rules out slender meadow katydid. This was a rare individual short-winged meadow katydid with long wings.

Next I turned to two species I have been seeking, which could overlap with the short-winged’s habitat. Straight-lanced meadow katydids in references and Internet photos lack the short-winged’s stripe pattern, instead often showing a diffuse blackish zone down that face of the femur. I went to photos of females I tentatively had identified as that species last year.

This one not only has an ovipositor much longer than the femur length, and lacks orange at the abdomen tip, but shows a femur color pattern different from the short-wingeds’ and consistent with straight-lanced reference photos. In fact it appears that the diffuse black zone is the same as the upper dark stripe on the short-winged, but differing in color and not sharply bounded. The lower stripe is there as well, but just as a trace of a line. I believe this individual may indeed have been a straight-lanced meadow katydid.

Others prove, on closer inspection, in fact to have been short-wingeds.

This young nymph has an ovipositor marginally longer than the femur, but has an instar or two to go until maturity and looks awfully orange around the abdomen. The femur color pattern clearly ties it to short-wingeds, and I think that is where this insect belongs.

The other species I need to sort out is the prairie meadow katydid. Few photos of this one are out there. In some there is no stripe pattern like the short-winged’s, in some there is a hint of one. For now I will need to focus on cerci (straighter, more pointed and with distinctly longer teeth than the short-winged male’s) and ovipositors (proportionately more curved than the short-winged female’s). I am encouraged, however, to continue looking for details of color pattern that might provide short-cuts to field identification at least in regional or local populations.

Take Your Kids to Work Day

by Carl Strang

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

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

Everyone gathered round when someone had something interesting to share.

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

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

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

They also tried out the SongFinder.

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

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

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

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

Mack Road Marsh

by Carl Strang

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

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

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

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

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

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