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.
The day produced 7 county records.
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 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 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.
Recent success in finding new species of sand-dwelling grasshoppers brought me back to Illinois Beach State Park in hope of continuing the run. On the beach I confirmed the presence of seaside grasshoppers, but was startled at the color contrast between them and the members of their species at Indiana Dunes National Lakeshore
Here is one of the Illinois Beach State Park hoppers.
And here is one from Indiana Dunes. Same species, different substrate, a nice study in natural selection.
Behind the foredune is a flat in which I found three species of singing grasshoppers, all in the band-winged grasshopper subfamily. The pattern continued of a larger species, a smaller one, with a couple Carolina grasshoppers thrown in for good measure.
The larger grasshopper was the by now familiar mottled sand grasshopper. These, like the seaside grasshoppers, were browner than their conspecifics in Indiana.
The small band-winged grasshopper at first made me think of the longhorn band-winged grasshopper.
The head protrudes above the pronotum, the size is the same, and the antennae look long.
However, in place of the bright red patch at the base of the hind wing, here it is transparent. The hind tibia pattern also is different. Both areas are hidden in the resting insect, and so not subject to selection pressure by predators.
This was a new species for me, the Kiowa rangeland grasshopper.
A little farther back from the shore, where the first trees appear, other insects may be found.
This is Dawson’s grasshopper, not a singing species (as you might guess from the dinky wings).
So far the meadow tree crickets I have found at Illinois Beach all have been four-spotteds. This one, too, as evidenced by the shapes of spots on the basal antenna segments.
Finally, in the savanna zone, the dominant singing grasshopper is Boll’s grasshopper.
Boll’s is in the same genus, Spharagemon, as the mottled sand grasshopper.
Like the mottled sand grasshopper, Boll’s grasshopper has bright yellow in the hind wings.
The easiest way to tell the two apart is to look at the angle of the back top edge of the pronotum (thorax shield). In Boll’s, here, the angle is more than 90 degrees. In the mottled sand grasshopper it is acute.
A final treat from that portion of my exploration was a big, beautiful female bird grasshopper laying eggs in the sand of the trail.
The non-singing grasshoppers of genus Schistocerca can be difficult to tell apart. I decided this one was S. alutacea, the leather-colored bird grasshopper.
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.
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.
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.
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 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.
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.
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.
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.
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, .
As another season of field research into the region’s singing insects winds down, I am starting to look back at the highlights. Some of these were chance encounters that provided new photo opportunities. For example, there was a weakened common true katydid I found on a trail at Waterfall Glen in broad daylight. I didn’t have a good photo of the species, and posed him after removing him from the hazardous trail.
Unfortunately I neglected to place his hind legs in a natural position.
Another species for which I want a better photo is the handsome trig. Some were singing on a cloudy day down in Fulton County, Indiana, and one came out in the open, but the low light resulted in a less than sharp image.
Tiny but colorful, the handsome trig lives in the southern part of the region I am surveying.
The Indiana Dunes area provided several photographs.
This oblong-winged katydid female was emitting single clicks in response to the more complex songs of nearby males.
A four-spotted tree cricket had escaped from my grasp before I could photograph it. While looking for it on the ground where it seemed to have gone, my headlamp revealed something better.
A female tinkling ground cricket, only the second member of the species I have seen (despite hearing hundreds).
A similar encounter came when I was trying to get a better photo of a melodious ground cricket at Indiana Dunes State Park. Digging through the leaf litter in the area from which a male’s song seemed to be coming, I turned up a female ground cricket.
When I examined the photos, though, I saw that the palps were white. This was a female confused ground cricket, another species that was singing in the area, and the first female confused I have seen.
One of the last places I visited this year was the Bong Recreation Area in Kenosha County, Wisconsin. The prairie area there is extensive, and has a good population of common meadow katydids.
Despite its name, the common meadow katydid is much less frequently encountered than two of its congeners, the gladiator and black-legged meadow katydids.
There were a few broad-winged bush katydids in the prairie, but I wasn’t successful in stalking one. This Texas bush katydid had to substitute.
Such encounters, sprinkled through the field season, make for good memories.
Recently I shared the story of a tree cricket that I suspected may be a prairie tree cricket. Last week I caught a second one which confirmed the identification, at least as far as I can tell.
As before, I put him in the freezer for a few minutes to immobilize him for photos.
Like the first, he was pale, and his extremities were brown rather than the black of a black-horned or Forbes’s tree cricket.
Beneath, he was dusky on the underside of the abdomen, but not black.
The critical feature is the spotting on the first two antenna segments.
In this one there was none of the smudging that fuzzed one edge of one of the spots on the first cricket. The spots on the first segment were large and fused. The spots on the second segment also were thick.
I was concerned that the pixilation in the photos might be distorting the appearance of spacing between the spots on the second segment, so I took the added step of examining them through the magnifying glass. The spaces were indeed being exaggerated by the camera. This further supports the case for prairie tree cricket.
So now I have the impression that all four species in the nigricornis group of meadow-dwelling tree crickets are present (I have found the four-spotted tree cricket in a few locations), and all may be common, in northeast Illinois. The prairie tree cricket, once a western species, has spread east thanks to agricultural practice. After catching the subject of this post I have had a devil of a time trying to get more (they seem to be staying close to the ground for warmth), so I may not make more progress in quantifying the relative numbers of the species this year. Unfortunately the pulse rates of prairie and black-horned tree cricket songs are nearly identical across the range of temperatures in which they sing. Otherwise I could do the survey entirely with recordings. The four-spotted seems to prefer grasses, but song perches for the other three are goldenrods, asters and even woody plants, so there is little to distinguish them in habitat preference. As for monitoring practice, it looks like this will simply have to be a category “nigricornis group” rather than a count of the separate species.
A return to Illinois Beach State Park was called for last week, as my first visit was early enough in the season that more singing insects could have become active since. For instance, gray ground crickets were not singing yet in early August, but by last week they were active.
Gray ground crickets are common in the scattered clumps of grasses and other plants behind the Great Lakes beaches.
Hearing is not seeing, however, and despite my best efforts I could not expose a gray ground cricket for a photograph. They were in the larger patches of vegetation and trapped oak leaves, and it was too easy for them to sneak away when I tried lifting leaves and plant stems to look for the hidden singers. That disappointment was relieved somewhat by an amusing dung beetle.
It was having difficulty moving this far-from-spherical chunk.
I had better luck with grasshoppers. Some members of the grasshopper subfamily Oedipodinae are in the park. These qualify as singing insects, as their displays include wing-rattling flights. I found two species. One, a darker form, was in the savanna near the Dead River.
This appears to be a Boll’s grasshopper, a relatively dark individual of the species. The yellow and black hind wings are hidden when folded at rest.
The beach was another grasshopper habitat.
Some grasshoppers prefer this more open vegetation structure.
A common species was pale and well camouflaged.
This one appears to be a seaside grasshopper.
In the night, I followed a tree cricket’s song as it trilled in the gray ground cricket habitat.
The antenna spots don’t show here, but they clearly revealed that this was a four-spotted tree cricket.
Robust coneheads had become common in the campground woods.
This male sings from a patch of big bluestem grass within the savanna.
I found a few more species to add to the site list, but none were particularly uncommon.
This is the third installment of a weekly series on singing insect species that supposedly occur in northeast Illinois or northwest Indiana but which I have yet to find after several years’ field work. Today I will consider two crickets representing different groups. They have in common a certain peculiarity in their range maps. We’ll start with the melodious ground cricket.
As you can see, the shaded area on this map (from the Singing Insects of North America website, or SINA) places nearly all of Illinois within the range of this species. However, that shaded area is computer generated from the only concrete records, which are represented by the black dots. Note that there are no dots anywhere in Illinois. As far as the SINA database goes, the species never has been found in Illinois, and there are only two records from northern Indiana. Illinois is included in the range thanks to a single record from northern Missouri. The species first was described from Ohio in 1957 by Edward S. Thomas and Richard Alexander. It is very similar to the Carolina ground cricket physically, but its song is described as a more melodious trill (lacking the Carolina’s discordant overlay of tones), and its habitat is narrower, limited to bogs and marshes. Even in Ohio there are few locations. The map shows melodius all over Florida, where Thomas Walker (who runs the excellent SINA site) is located.
The next example is the prairie tree cricket.
Northeast Illinois and northwest Indiana are included in the range for this species thanks to two records for Cook County, Illinois, from 1934 and 1935. On the other hand, two records from Iowa probably would have led the computer to shade our region even without those old Cook County records. I mentioned in an earlier post this year that I am looking for prairie tree crickets in sweep samples from meadow and prairie areas, but so far have found only four-spotted, and black-horned/Forbes’s tree crickets in that sampling.
These examples underline the need to be careful in thinking about the geographic range of species. Some singing insects are relatively general in their habitat choice, or tolerant of human alterations in the landscape, or simply have been fortunate to have passed through the sieve of history unscathed. They are the common ones. Shaded areas in range maps like SINA’s represent them best. Other species are much pickier, or their lower densities have made them subject to more frequent local extinctions over time. They are best represented by dots. The best example I have encountered here is the sphagnum ground cricket, which appears indeed to be limited to the narrow confines of sphagnum moss areas. These were more ubiquitous in the broad zone which trailed the last continental glacier north, but then in southern parts became isolated in little bits here and there.
I am not removing melodious ground crickets or prairie tree crickets from my hypothetical list for our region, but until I find them I will not list them as definitely occurring here today.
Some tree crickets live in trees, others live among the trees in the forest understory, but there are a few species that inhabit meadow and prairie areas. Last week I looked at some of these when I did some sweep sampling in two locations. The first was Springbrook Prairie Forest Preserve.
This low area dominated by big bluestem grass was part of the habitat I surveyed.
I went there in hope of finding more of the cicadas, tentatively identified as swamp cicadas, that I heard there last year. At the time the song seemed definitive, but I since have learned that Linne’s cicadas sometimes have songs that are similar, and so I was hoping to find one to photograph. All was quiet, however. That’s not necessarily a bad sign. If this is indeed a new population (DuPage is north of the published range for swamp cicadas), they might not be emerging every year. In any case, while I was waiting for singing cicadas I did some sweep sampling, and turned up several tree crickets.
Here is one of the individuals I caught in a goldenrod-dominated area. It has a dark stripe down the top of the head and pronotum, as well as dark antennae. Despite the otherwise pale color, these features point to the black-horned/Forbes’s pair of tree cricket sibling species.
Proper identification of these tree crickets requires an examination of spotting on the basal two antenna segments.
Here the spots on the first, basal segment are very large and smudged. Those on the second segment likewise, to the point where the entire segment looks black at first glance. Also note the dark area on the underside of this tree cricket’s abdomen. All these features point to black-horned/Forbes’s.
The next cricket, from the big bluestem area, is much paler, and shows a different antennal spot pattern.
Here the spots all are smaller, and the outer ones on the basal segments are round and have smeared edges. This is a four-spotted tree cricket.
Another Springbrook tree cricket was more ambiguous.
This individual happily nibbling my finger shows spotting that falls within the range of overlap for four-spotted and black-horned/Forbes’s tree crickets. The most definitive spot is the outer one on the basal segment. It appears just large enough to rule out four-spotted.
The next day I did some sweep sampling at Mayslake Forest Preserve.
The sample included several pale tree crickets like this.
The cricket in that last photo had the following spot pattern.
This is a clear indicator of four-spotted tree cricket, the outer spots on both segments small, round, and faded looking.
A final example showed even fainter spots.
Again I identified this one as a four-spotted tree cricket.
There is a fourth meadow species that I have been watching for but so far have not found. The prairie tree cricket is generally pale, like the four-spotted. Its antenna spots are heavy and close together, but without the blurred smudging of the black-horned/Forbes’s species pair.
During a recent Take Your Kids To Work Day program at Forest Preserve District headquarters in Danada Forest Preserve, I was one of the teachers in an entomology unit. An adult tree cricket turned up in a sweep net sample, and I decided to try for photos.
As seems common with tree crickets, this one was interested in palpating my finger (often they’ll nibble as well). The shot I was seeking was a photo of the insect with its antennae held back, preferably taken from a quartering angle. I did get a usable one.
Those dark spots on the first two antenna segments often are distinctive enough for species identification. The most recent authoritative drawings and descriptions I have seen were contributed by a leading researcher on tree crickets, Tom Walker, in the Field Guide to Grasshoppers, Katydids and Crickets of the United States (2004, Cornell University Press), which he co-authored with John L. Capinera and Ralph D. Scott. The Danada cricket falls into a middle ground in the drawings, conceivably fitting four-spotted, prairie, or black-horned/Forbes’s.
Until I saw the photo I didn’t expect this. The cricket overall was very pale, and I had ruled out the black-horned/Forbes’s sibling species pair because they typically have dark areas on the head, pronotum (top of thorax), and underside of the abdomen. If I had to choose, though, based on antennal spotting alone, I would say this individual was a black-horned or Forbes’s tree cricket, albeit at one extreme end of their range of variation (for more on that species pair, see my post of last autumn).
In previous years I have examined a number of tree crickets from the area where this one was caught, and all have been in the black-horned/Forbes’s darker color pattern. The only clear result is that I need more experience with these four prairie-to-shrubby-meadow tree cricket species.