Sarett Nature Center

by Carl Strang

Sarett Nature Center is located in northern Berrien County, Michigan. It has some high quality habitats, in particular a good sized fen and some upland forest. Glimpses of the facility’s education program that I got when I visited there last week pointed to high quality in that service, as well. Sarett’s singing insects provided a couple highlights worth sharing here.

While checking out a restored prairie and its adjacent tree line, I encountered a Forbes’s tree cricket laying eggs.

The female arched her body so as to bring her ovipositor in perpendicular to the sassafras stem. The line of eggs was around 3 inches long.

The female arched her body so as to bring her ovipositor in perpendicular to the sassafras stem. The line of eggs was around 3 inches long.

The fen was rich in sedges and other native plants.

A boardwalk provides access to the fen’s interior.

A boardwalk provides access to the fen’s interior.

Through the SongFinder I heard an unfamiliar insect song, a rapid tapping sound.

The singers proved to be black-sided meadow katydids.

The singers proved to be black-sided meadow katydids.

When I have encountered this species before, its song was overwhelmed by those of black-legged meadow katydids. Those were few in the fen. It became clear that the black-sideds were concentrated in portions of the fen that had coarse-stemmed red-osier dogwoods or broad-leaved cattails.

I left Sarett satisfied with my experience there, but a couple hours of light remained, and the day’s big highlight was still ahead…

 

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.

 

Return to Berrien

by Carl Strang

Earlier this season I scouted some new sites in Berrien County, Michigan, and on Sunday I returned to see what singing insects I could find in the early portion of the peak season. A first quick stop at Mud Lake Bog produced a hoped-for population of sphagnum ground crickets, and I was reminded how utterly teeny tiny they are.

Most of the day, and a return trip in the evening, went into a place in the eastern part of the county called Chikaming Township Park. If this were Illinois, I wouldn’t expect much from a park district administered at the township level, but this is a good and well maintained site, and it yielded a pile of county records for my study. One of these was provided by a female curve-tailed bush katydid that flew to a landing right in front of me on one of the trails.

The dark-tipped green ovipositor with this shape and proportions, along with the katydid’s overall size and the habitat, permitted the identification.

The dark-tipped green ovipositor with this shape and proportions, along with the katydid’s overall size and the habitat, permitted the identification.

After release, she hung around long enough to let me take a single usable, if not absolutely sharp, photo.

After release, she hung around long enough to let me take a single usable, if not absolutely sharp, photo.

Perhaps the most bizarre observation came as a result of the day’s odd weather. I drove through intermittent rain to get to Berrien County, and waited out the last shower before going out onto the Mud Lake Bog boardwalk. Dark clouds remained until mid-afternoon, but they slowly drifted east and the sun was revealed at 4:00 local (eastern) time. Almost immediately, Chikaming’s swamp cicadas began to sing. These generally are limited to mornings, but here they were going in the late afternoon. This site proved to have the largest concentration I have encountered to date. At one point I wandered into a song battle taking place among a trio of males in a meadow with scattered tree saplings. One allowed a close approach.

None of our other cicadas matches the swamp cicada’s heavy black coloration.

None of our other cicadas matches the swamp cicada’s heavy black coloration.

Later in the evening I was able to pick up some additional species.

Among them was this Forbes’s tree cricket.

Among them was this Forbes’s tree cricket.

The highlight of the day, though, came at another site, Galien River County Park. I had set a goal for this season of listening for spotted ground crickets, which historically have been documented in several Chicago region counties, but which I had not noted to date. Described as a forest species, the spotted ground cricket’s song to my ear is similar to that of a common and widespread species, the Carolina ground cricket. I realized that while some of the forest crickets at Galien River indeed were Carolina ground crickets, others sounded a little different. I made recordings, and listened carefully, and was pleased to conclude that spotted ground crickets were there as well.

An example of a spotted ground cricket location.

An example of a spotted ground cricket location.

The songs have a similar tonal quality and pitch range to my ear. Where the Carolina ground cricket’s song is a steady purr with intervals of added overtones, the spotted ground cricket’s song is composed of regular pulses (about 4 per second), has no overtones, and lacks the continuous steady sound.

 

Return to Midewin

by Carl Strang

Recently I spent an enjoyable afternoon at the Midewin National Tallgrass Prairie, in Will County, Illinois. My main target was a swale in the northwestern portion of the property.

In one place the swale expands into a ponded area that in this wet year was around 50m wide and a few hundred long.

In one place the swale expands into a ponded area that in this wet year was around 50m wide and a few hundred long.

I added 3 county species records in and around the swale, but all are common in the region and so not the exciting rarities I’d hoped for.

This Forbes’s tree cricket was one of the three. It was perhaps the darkest individual I have seen in Illinois, and more typical of the Indiana coloration in my experience.

This Forbes’s tree cricket was one of the three. It was perhaps the darkest individual I have seen in Illinois, and more typical of the Indiana coloration in my experience.

As I returned to my car, wading through a nicely developing restored prairie, I spotted an unfamiliar grasshopper.

It held still while I took side and dorsal photographs. The color pattern and sculpturing pointed to the band-winged grasshopper subfamily.

It held still while I took side and dorsal photographs. The color pattern and sculpturing pointed to the band-winged grasshopper subfamily.

Note the white X marking on the pronotum (dorsal thorax). That rang a bell, and ultimately helped with the identification.

Note the white X marking on the pronotum (dorsal thorax). That rang a bell, and ultimately helped with the identification.

Unfortunately the hopper evaded me when I tried to catch it so as to check out the hind wing color. As I continued to walk out I saw a couple displaying grasshoppers with bright yellow hind wings, which I was unable to see up close. I made the assumption that they were the same as the photographed hopper, but this proved not to be the case. It turned out to have been a dusky grasshopper, Encoptolophus sordidus, which has an essentially colorless hind wing. It was the first of that species I have found, which always is exciting, but now I know there’s also a yellow-winged species I will have to go back and hunt down on a future visit.

While I was photographing the dusky grasshopper, a nearby movement caught my eye, and led me to a new experience. It was a ballooning spider, half an inch long. I had heard of this but never seen it, and did not expect that such a large individual could travel in that way. The spider sends out a strand of silk which grabs the wind and carries the spider through the air.

The spider had landed on a stalk, and paused long enough for me to get some photos. I haven’t had time yet to try for an ID.

The spider had landed on a stalk, and paused long enough for me to get some photos. I haven’t had time yet to try for an ID.

The spider didn’t wait long before it turned to face into the wind.

The spider didn’t wait long before it turned to face into the wind.

It began shooting out new strands of silk, obviously not satisfied that it had traveled far enough.

It began shooting out new strands of silk, obviously not satisfied that it had traveled far enough.

As I continued my walk to the car I noticed several strands of silk streaming from plant tops, and felt that I had learned something new about them.

I’ll close with a couple photos from other parts of Midewin.

This female short-winged green grasshopper was a county record.

This female short-winged green grasshopper was a county record.

A female fall field cricket posed nicely on a trail.

A female fall field cricket posed nicely on a trail.

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.

 

Sound Ideas: Trilling Tree Crickets

by Carl Strang

Today I wish to share recordings of 4 species of our tree crickets, which have in common songs that are continuous (rather than interrupted) trills. I will order them along a typical habitat gradient, from grasses to mixed grasses and forbs to mixed forbs and shrubs to trees (specifically, conifers).

The four-spotted tree cricket seems to prefer to sing from grass stems.

Four-spotted tree crickets are pale.

Four-spotted tree crickets are pale.

The song is a continuous clear trill:

Very abundant late in the season, Forbes’s tree cricket prefers forbs or vines.

Forbes’s tree cricket is highly variable, but usually has some dark markings.

Forbes’s tree cricket is highly variable, but usually has some dark markings.

Here is a recording from last year:

There is an interesting issue surrounding these first two songs, in my mind. I know of other singing insect students who, like me, at least sometimes can distinguish the songs of four-spotted and Forbes’s tree crickets, but we describe them with different language. To me, the four-spotted’s song has more of a clear, tone-like quality, while the Forbes’s song has a discordant tone that others apparently don’t hear. Others point to the difference in pulse rate (much faster in Forbes’s, but I need a computer analysis of a recording to tell that difference). This is the best example I have found of how describing insect songs in words can be difficult, and may in some cases be impossible.

Woodland shrubby understories to masses of forbs in open places near wooded edges are habitat for our third species, the broad-winged tree cricket. Here is its song:

Broad-winged tree crickets are distinguished by the wide wings and the raspberry coloration on the head and antenna bases.

Broad-winged tree crickets are distinguished by the wide wings and the raspberry coloration on the head and antenna bases.

To my ear, this song has a richer tone, and usually is lower in pitch than other trilling tree crickets at the same temperature.

I’ll close with the pine tree cricket, perhaps the most beautiful of the four.

The red-browns and pale greens provide good camouflage in a habitat of coniferous trees.

The red-browns and pale greens provide good camouflage in a habitat of coniferous trees.

The following recording was made indoors, from a caged male (you can hear the splashing of the aquarium pump in the background):

Again the trill is continuous and similar to the others, especially the four-spotted tree cricket, but the source of the sound in a pine, spruce or cedar (usually in a grove of them) is a dead give-away.

Burn Aftermath

by Carl Strang

Mayslake Forest Preserve had much of its acreage burned for management purposes last spring, as described earlier. One result, aided by good amounts of seasonal rains, was a very lush, tall growth of prairie vegetation.

Part of one of Mayslake’s prairies on August 12.

Part of one of Mayslake’s prairies on August 12.

What impact did this have on the prairie insects, in particular the singing insects? I expected the species that lay their eggs in the tops of prairie plants would be impacted the most, but those that lay their eggs in the soil would be relatively unharmed. It was clear, though, that despite the unusual completeness of the burn, small patches of prairie here and there were missed by the fire, as were wetland and woodland edges, and there were portions of the preserve not included in the burn plan. These provided a reservoir from which affected species might spread.

My impression through the season was that the numbers of fall field crickets (a species which lays its eggs in the soil) were down from last year, but the numbers don’t bear this out. Counts on the whole in the various habitats are similar between this year and last. Likewise, the 3 species of common ground crickets are so abundant in all habitats that no quantitative comparison seems necessary.

Greenstriped grasshoppers overwinter as nymphs, and so are more vulnerable. If anything, however, their numbers seemed somewhat larger in all habitats, including burned ones.

Greenstriped grasshopper nymph

Greenstriped grasshopper nymph

Unfortunately, confusion about the species identity of meadow-dwelling tree crickets (described in a post earlier this week) prevented my gathering quantitative data last year. I did record numbers this year, though, and attended their locations through the season. It was clear that the earliest singers in this group were concentrated in unburned areas and around the edges of burned areas, where they might have hatched from eggs in the unburned adjacent habitats. As the season progressed, though, these tree crickets (mainly Forbes’s tree crickets) proved to be very mobile, and spilled into the hearts of the burned areas (where the forage no doubt was richer thanks to the burn, and where there was an advantage to escape the competition). Though numbers overall may have been down a little, there were plenty of these tree crickets to ensure a rapid population recovery.

As for meadow katydids, they all to some extent concentrate in wetlands, which were scorched in places but not thoroughly burned. There again appeared to be plenty of survivors to reproduce and fill the habitat.

Perhaps the most interesting observation relevant to this question this year was a big drop in wasps of the genus Sphex. There were a lot of these last year, crowding into the areas where swamp milkweeds were blooming. The great black wasp and great golden digger specialize in capturing katydids to feed their young, and potentially can influence populations significantly. I saw only a very few of those wasps this year. As they overwinter underground, I doubt the fire had anything to do with their absence. Whatever the cause, their departure further assured a successful reproductive season for the katydids of Mayslake.

Great golden digger

Great golden digger

The upshot of all of this is that the extensive spring burns, while they may have had some minor and spotty effects on singing insect populations (and, by extension, other invertebrates), did not devastate any populations as far as I can tell. This was somewhat surprising, but in retrospect it becomes clear that it would take an extraordinarily complete and extensive burn to have a long-term impact. Refugia within and without the burn area seem likely to carry populations through enough to recover from this disturbance.

Tree Cricket Clarity

by Carl Strang

A year ago I was struggling with the identification of a group of four meadow-dwelling tree cricket species that reportedly live in northeast Illinois and northwest Indiana. They have been determined to be close relatives, and two of them had been established as sibling species by Thomas Walker of the University of Florida: the black-horned tree cricket and Forbes’s tree cricket are physically alike, and can be distinguished only by the pulse rate of their songs, which requires the analysis of sound recordings.

Forbes’s and black-horned tree crickets can be very black, as shown in this individual at Pinhook Bog in Indiana.

Forbes’s and black-horned tree crickets can be very black, as shown in this individual at Pinhook Bog in Indiana.

This is a paler representative of the species pair from the Great Marsh, also in the Indiana Dunes National Lakeshore.

This is a paler representative of the species pair from the Great Marsh, also in the Indiana Dunes National Lakeshore.

One member of this species group, the four-spotted tree cricket, is readily identified. It is pale, and has a distinctive pattern of spots on the basal segments of its antennae.

All four of the spots on the two lowest antenna segments of this four-spotted tree cricket in Fulton County, Indiana, are relatively small and well separated. The outer spot on the basal segment is nearly round.

All four of the spots on the two lowest antenna segments of this four-spotted tree cricket in Fulton County, Indiana, are relatively small and well separated. The outer spot on the basal segment is nearly round.

The final species is the prairie tree cricket. I thought I found this species last year at Mayslake Forest Preserve, again following the long-established focus on antenna spot patterns.

This individual was generally quite pale, and the antenna spots matched reference drawings for the prairie tree cricket.

This individual was generally quite pale, and the antenna spots matched reference drawings for the prairie tree cricket.

When I analyzed my sound recordings of the songs of prairie/black-horned/Forbes’s tree crickets from Mayslake and other DuPage County locations, however, they generally fell out as Forbes’s, though some recordings made at lower temperatures were somewhat ambiguous.

This confusion has been largely resolved, now, thanks to the recently completed Ph.D. thesis work of Laurel Symes. She traveled widely in her study of these species, collecting specimens and analyzing their songs and their genetic relationships. Though her focus was on female response to male songs, and the associated behavioral, ecological and evolutionary implications, the information she collected also is very helpful to my regional survey of singing insects.

Though she doesn’t say this herself in anything I have seen, it seems clear that we need to throw the time-honored focus on antenna spot patterns out the window for three of the four species, though it still holds for the four-spotted tree cricket. Laurel found a geographic separation between black-horned and Forbes’s tree crickets, with a zone of contact that may involve some hybridization. That zone is in Ohio, safely east of the Chicago region. Unless something new emerges in the future, I am following Nancy Collins in calling all our local ones Forbes’s tree crickets as a result of Laurel’s research.

As for the prairie tree cricket, it, too, seems not to be in the region, occurring well south and west of us. I will retain it on the hypothetical list, though, because Laurel’s results were less certain on this point.  In any case, as long as the temperature is warm (at least 68F), the remaining three species can be distinguished from sound recordings, so they need not be captured. All you need is the temperature, the graphs relating pulse rate to temperature, and a pulse rate count from the recording. At the standard temperature of 25C, four-spotted tree crickets have a pulse rate of 40 per second, prairie tree crickets 51 per second, and Forbes’s tree crickets 65 per second. Laurel found that selective pressures on male song and female choice keep these quite separate and narrowly defined, .

Song Analysis

by Carl Strang

One of my goals this autumn was to begin sorting out the meadow dwelling tree crickets of the nigricornis species group at Mayslake Forest Preserve. In earlier posts I shared some photos that pointed to a mix of species, but now I have studied their songs, and the results prove to be complicated. One individual was straightforward. He was unique in having an abdomen that was black beneath.

I immobilized him briefly in the freezer for photos.

I immobilized him briefly in the freezer for photos.

His antennal spots clearly distinguished him as either a black-horned tree cricket or a Forbes’s tree cricket.

There was clear separation between the spots on the second antenna segment, and those spots were narrow.

There was clear separation between the spots on the second antenna segment, and those spots were narrow.

When I looked at my recording of his song in the Audacity sound analysis program (available as a free download), the pulse rate clearly was that of a black-horned tree cricket.

The program allows the pulse rate to be counted, in this instance the interval between the 6-second and 6.5-second point in the recording. The pulse rate of 36-37 per second at 65.5F is unambiguously that of a black-horned.

The program allows the pulse rate to be counted, in this instance the interval between the 6-second and 6.5-second point in the recording. The pulse rate of 36-37 per second at 65.5F is unambiguously that of a black-horned.

The other tree crickets were problematic. Here is the most ambiguous case. His antenna spots, along with his generally pale coloration, said he was a prairie tree cricket.

The spots on the second antenna segment were thick, and had a very narrow space between them.

The spots on the second antenna segment were thick, and had a very narrow space between them.

On the other hand, his song had a very rapid pulse rate.

A pulse rate of 48 at 68F is close to that of a Forbes’s tree cricket.

A pulse rate of 48 at 68F is close to that of a Forbes’s tree cricket.

All the other tree crickets I tested had songs most like Forbes’s, but only one had the antenna spots to match. The others either were closer to those of the prairie tree cricket, or were ambiguous. The literature I have seen cannot carry me any farther. My next step will be to look at nigricornis-group tree crickets at other sites in 2013, and hope for enlightenment.

Black-horned Subtleties

by Carl Strang

Lately most of the members of the nigricornis group of tree crickets I have been catching at Mayslake Forest Preserve have proved to be prairie tree crickets. Last week I found an exception that brought out some of the subtle distinctions among these insects.

The broad black band on the underside of the abdomen narrowed this one down to being either a black-horned or a Forbes’s tree cricket.

The tips of the legs and antennae likewise were black. However, he was pale on top.

There was a diffuse darker stripe down the top of the head and pronotum, but so pale as to be ambiguous.

With this group of species it is a good idea always to look at the antenna spots. In this one the spots on the basal segment were large, fused and fairly well defined.

The spots on the second segment were very narrow, however, and well separated, as they should be in this species pair.

Another lesson I learned from this cricket was the importance of viewing angle on those second-segment spots. You need to look straight down on the inner spot with respect to its own position, rather than from the cricket’s mid-line, which gives only a slightly tangential view of the critical spot. After taking the photos I took the cricket home and he sang for me, so later the recording should allow me to determine which of the two sibling species he was.

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