Block Count Summary

by Carl Strang

Neighborhood block counts are a survey method I have developed in my singing insects study. They consist of walks around the block in my residential neighborhood in Warrenville. I record the time and temperature, and count only the insects whose individual songs I can distinguish from the general background of tree cricket and ground cricket songs. I try to include a mix of times, especially early in the season to include cicadas, but concentrate most of the effort after dark when most species are singing. The overall species count in 2011 was 14 (no new species this year).

One of the streets on the block.

Most of these insects do not occur in high enough numbers to permit statistical comparisons between years. The high counts for each species this year were as follows: 1 for fall field cricket, jumping bush cricket, Say’s trig, and Davis’s tree cricket; 2 for Allard’s ground cricket and dog day cicada; 3 for snowy tree cricket, 4 for narrow-winged tree cricket, 5 for common true katydid, 8 for two-spotted tree cricket, 10 for Linne’s cicada, 14 for Carolina ground cricket, 16 for greater anglewing, and 26 for striped ground cricket. Most of these are typical of the past five years. Apart from statistical comparisons to follow, there seems to have been a decline in fall field crickets over that period (high counts of 5 in 2007, 4 in 2006, and 1 in the recent years, but in 2011 that count was on only one occasion).

Only three species occur consistently in large enough numbers to justify statistical comparisons between years. There never have been statistically significant differences between adjacent years in striped ground cricket counts, and the same was true in this year’s comparison with 2010 (overall medians 14.5 in both years; Mann-Whitney U-test, z = -0.14, P>0.01). Carolina ground crickets likewise were not different (median 4 in 2010, 7 in 2011; z = -2.07, P>0.01). Greater anglewing counts did show a statistically significant increase over last year (median 1 in 2010, 4 in 2011; z = -3.30, P < 0.01), and in general they and the fall field crickets have been the most volatile.

Braidwood Dunes etc.

by Carl Strang

Last week I traveled to southern Will County to seek singing insects in sand country. My main stop was the Braidwood Dunes Natural Area, managed by the Forest Preserve District of Will County. I only got into part of it, and what I saw was outstanding.

There was an extensive dry prairie on sand soil dominated by little bluestem, for instance.

That prairie hosted the largest concentration of common meadow katydids I have encountered to date. In DuPage County I have found only scattered individuals and tiny groups.

It was a windy day, and the katydids were very shy. I took maybe 20 photos to get a couple that were only slightly blurry.

One of the species I specifically was seeking was the gray ground cricket. In places that were very similar in vegetation and soil to those where I heard this species at Illinois Beach State Park, I heard trills that sounded the same in memory.

One of the places where I heard probable gray ground crickets.

I made a recording, and cannot distinguish the sound, in trill speed or tonal quality or pitch, from that in a recording I made at Whitefish Dunes in the U.P. of Michigan a couple years ago (where the only candidate is gray ground cricket). Having no permit, I was not about to try and capture, let alone collect, specimens, so comparisons of recordings will have to do for now.

Otherwise, I heard mainly common species at Braidwood Dunes. I was happy to discover long-spurred meadow katydids in a wooded area, and I also made an observation that at first seemed trivial but later proved more substantive. It seemed that the Allard’s ground crickets were slowing their trill by a huge amount in shaded areas under trees. By the time I made the day’s final stop at Forsythe Woods Forest Preserve, I had realized that the slow ones might have been tinkling ground crickets, a sibling species of Allard’s. I made a recording of one there, and it proved identical in tonal quality and pitch, and in fact had a slightly longer spacing between notes, than the confirmed recording of a tinkling ground cricket by Lang Elliott and Wil Hershberger. This experience highlighted the emphasis here and there in the literature that the tinkling ground cricket is a species mainly of dry woodland edges.

My other stops were along the Kankakee River in my continuing search for variegated ground crickets.

I stopped first at a place with a long sandy river edge.

No ground crickets in the sand.

I also found a stretch with a significant pebbly shore.

The only ground cricket here was a single Carolina ground cricket. That’s it for seeking variegateds this year. Next year I may try for them in areas where they apparently are more concentrated, in southern Indiana. Once I have experience with the species, I may have a better idea of where to look in northeast Illinois.

Sphagnum Ground Cricket

by Carl Strang

The sphagnum ground cricket was a species I had sought but failed to find in DuPage County last year. Apparently low vernal pool areas in our woodlands are not sufficiently close to the sphagnum habitat the species requires, and as we have no sphagnum in DuPage I would need to look elsewhere. When my plans for Illinois Beach State Park were thwarted by the south unit’s closure, I decided to move on from the north unit (where I had been successful in my search for gray ground crickets) to Volo Bog State Natural Area.

This is the center of the main bog, accessible by a well maintained boardwalk.

The outermost zone of the bog was not promising. There was no sphagnum that I could see, mainly marsh plants, with the prominent singing insects being black-legged meadow katydids and Carolina ground crickets.

Here is the marsh habitat, with the next, shrubby zone in the background.

As I entered the next concentric ring of habitat, working my way toward the bog’s center, a mix of shrubs was dominant. The black-legs and Carolinas petered out. I began to see sphagnum moss.

The shrub and sphagnum habitat at Volo Bog.

At first I heard mainly Say’s trigs, but it seemed there was something else. I got out the SongFinder, and its frequency-lowering function allowed me to identify a second, fainter, more rapid trill. When I then removed the headphones I found that I could pick out the second trill, which matched my memory of reference recordings of sphagnum ground crickets. I got down on my hands and knees at the edge of the  boardwalk, probing the sphagnum lightly with my fingers, and that was all it took to get some photo ops.

This nymph was the first sphagnum ground cricket I saw. I was struck by its beautiful coloration, especially the mottling and white dots on the hind legs.

Adults seemed mainly black.

The mottling is subdued on the legs, but still present on this adult. The eyes are large and brown.

There were so many singing at once that I was not able to pick out the ends of any trills. The song seems very like that of the gray ground cricket, but fainter, being a very rapid, level, high-pitched trill (more rapid than those of Allard’s ground crickets or Say’s trigs). I am guessing that the gray ground cricket needs to be louder in its more open, wind-swept dune habitat.

Peak Singing Insect Season Begins

by Carl Strang

By this point in the season we are hearing nearly all the common singing insects in northeast Illinois. First song dates on the whole have been in line with those of recent years, but a few have been relatively late and one was comparatively early.

Snowy tree cricket

My own first observations of singing males typical of residential neighborhoods have included Carolina ground cricket (19 July), common true katydid (also 19 July, a relatively early start for that species), Allard’s ground cricket (22 July), snowy tree cricket (29 July), fall field cricket (30 July, a relatively late start but I had been out of town for a week), two-spotted tree cricket (31 July), Say’s trig (31 July), and greater angle-winged katydid (4 August).

Greater angle-winged katydid

I didn’t get into forests at night until the Roger Raccoon Club campout, so my first date of August 3 for oblong-winged and rattler round-winged katydids has limited meaning. Another forest species that may have started up before my first observation of August 2 was the confused ground cricket.

Black-legged meadow katydid

Our most common large meadow katydid, the black-legged, started up around August 2, a relatively late start for this wetland-edge insect.

A Week of Firsts

by Carl Strang

The past week brought the true beginning of the singing insects season. Though a full work week and other obligations filled my time, I was able to take advantage of what I have learned in past seasons to make some observations that were valuable to me.

For instance, last year I finally nailed down features of the two-spotted tree cricket’s song that removed my earlier uncertainty. The breakthrough came when I found this male, who had chewed a hole in a grape leaf to create a baffle that amplified and/or directed his song.

Finally seeing one of his kind in action, I was able to define the song of that species by the irregular length of its trills, some reaching 7 seconds’ length or more, the spaces between trills being either very brief, or longer but filled with stuttering sounds, and the strained or discordant quality of the sound.

That discovery allowed me to be confident in identifying the first two-spotteds singing in DuPage County, Illinois, this year, on July 12. That is the earliest song date I have for that species, by 5 days.

I also heard the year’s first ground crickets in DuPage. I had been gone a week, and returned to hear striped (photo below) and Allard’s ground crickets on July 12, and Carolina ground crickets on the 13th (I had heard all three near Culver, Indiana, on July 8). Though not the earliest ever, all three species were singing near the earliest first song dates I have noted for them since my study began in 2006.

Mayslake Forest Preserve is one of the DuPage County sites where there are fall field crickets but no spring field crickets. So, when I heard a field cricket song there on July 14 I marked the beginning of that species’ singing season (female shown).

During First Folio Theater’s evening performance of Twelfth Night at Mayslake I heard a few protean shieldbacks singing, my first record of that katydid species on that preserve (female shown).

Finally, I heard my first sword-bearing coneheads of the year while driving to Culver on the evening of July 16.

There are plenty of other species yet to begin, but it feels like the singing insects season has begun in earnest.

Winter Comes to Mayslake

by Carl Strang

November had been unseasonably warm. I heard Carolina and Allard’s ground crickets singing on December 1, the latest I have heard any singing insects in DuPage County. But it wasn’t to last. A major winter storm, complete with strong winds, a significant snowfall, and temperatures dropping to the single digits Fahrenheit, arrived in the second week of December.

Mayslake Forest Preserve, like most of the eastern U.S., received its blanket of snow, though only 2-3 inches accumulated locally. The low temperatures froze the lakes. Coyotes again could use the ice for quick short cuts.

The snow revealed that the coyotes were covering the entire preserve, though apparently singly; I saw no signs of tandem hunting. Birds in evidence were mainly consumers of seeds, like these mourning doves,

and this cardinal,

here caught in the act of reaching for fruit.

Block Count Results

by Carl Strang

Earlier in the season I described my block counts of singing insects, in which I walk around the block where I live, counting the singing insects I hear. In these counts I heard 13 species in 2009, compared to 15 in 2008. The two missing species were the dog day and scissor-grinder cicadas, both of which I heard on my block at times other than sampling sessions.

Only 3 species have been present in large enough numbers to allow comparisons between years. Most abundant is the striped ground cricket, with median counts of 13, 14.5, and 12 for 2007, 2008 and 2009, respectively*. Statistical tests found no differences among years in the striped ground cricket.

Median counts of Carolina ground crickets were 3, 3, and 7 for the three years. The change from 2008 to 2009 was statistically significant. The third species, the greater angle-winged katydid, produced median counts of 7, 1, and 0. The drop between 2007 and 2008 was statistically significant, but that from 2008 to 2009 was not.

The other species I have noted in my neighborhood, in rough descending order of abundance, are two-spotted tree cricket, snowy tree cricket, fall field cricket, narrow-winged tree cricket, Linne’s cicada, common true katydid, Allard’s ground cricket, and a few species I have heard very infrequently: jumping bush cricket, Say’s trig, Davis’s tree cricket and possibly fork-tailed bush katydid.

*For those interested in the technical details, I included only counts in August-October, the months when these species appeared consistently. Total numbers of counts were 49, 46 and 35 in the three years, respectively. I am very conservative in my use of statistical tests. Here I used the large-sample version of the Mann-Whitney U-test, a nonparametric test which produces (ironically?) a z test statistic. Non-parametric tests are needed for count data, and I seldom see anything like a normal distribution in the aspects of nature I study, anyway. Test statistic values for striped ground cricket counts were z = -0.73 for 2007 vs. 2008, and -1.58 for 2008 vs. 2009, both P > 0.01. Again, being conservative, I use the 1% rather than the 5% level of error. Carolina ground cricket counts showed no change between 2007 and 2008 (z = -0.68, P > 0.01), and an increase from 2008 to 2009 (z = -3.32, P < 0.01). Greater angle-wing counts showed a decrease from 2007 to 2008 (z = -3.33, P < 0.01), but no change from 2008 to 2009 (z = 0.32, P > 0.01).

Singing Insects at Whitefish Point

by Carl Strang

The third goal of my Upper Peninsula trip last week was to study the singing insects there. Compared to northern Illinois, the singing insect fauna was very limited. At night the campground at Tahquamenon Falls State Park was quiet, except for the amazing snoring of one of my neighbors, thankfully only for one night. During the day the principal singing insect in the forest was the dog-day cicada.

Open areas such as Whitefish Point had more to offer. I was especially pleased to find that gray ground crickets are common there. Like all ground crickets these stayed well hidden. Here is typical habitat.

Gray ground cricket habitat b

This species is known from dunes areas around southern Lake Michigan, but the only time I was at Illinois Beach State Park listening for them was a windy day and I could not hear them clearly. At Whitefish Point I easily distinguished their song. Though the trills seem composed of discrete notes like those of Allard’s ground cricket, they are at least three times faster (Allard’s were there as well, making comparison easy). Also, the trills were not continuous but rather were interrupted by brief pauses that were spaced regularly in some individuals but at varying intervals in others. In addition to Allard’s, familiar crickets at Whitefish Point were fall field crickets and Carolina ground crickets.

Whitefish Point also was home to two singing grasshoppers that represented the two forms of grasshopper song production. One of them was a crepitating species like Illinois’ greenstriped grasshopper. My references point to the clearwinged grasshopper, Camnula pellucida, as the identification, though I am not certain.

Clearwinged grasshopper 2b

In the photo the male is on the left. Crepitation is sound production by the rattling or snapping of the wings in flight. In this species the rattle is much louder than that of the greenstriped grasshopper. Clearwinged grasshoppers occupied the more open dunes areas. The other form of sound production is called stridulation. A common grasshopper that stayed close to woody plants at Whitefish Point produced loud “zuzz-zuzz-zuzz” sounds with this method. My best stab at identification is Thomas’s broad-winged grasshopper, Chloealtis abdominalis.

Thomas's broad-winged grasshopper 3b

The black areas on the sides of the pronotum seem to point to that species. Another photo, taken just as the grasshopper turned to put some distance between itself and my camera, shows that from behind the legs have a lot of red on them.

Thomas's broad-winged grasshopper 5b

In stridulation, both legs are lifted and lowered at once, and rows of pegs on them rub against the folded wings to produce the sound.

I also found broad-winged bush katydids at Whitefish Point, but I will hold that discussion for a later time.

Say’s Trig

by Carl Strang

The trigs are a group of tiny crickets which, like the ground crickets, are heard much more than they are seen. The common species in northeast Illinois is Say’s trig. Here’s a female; the short curved ovipositor extending from her abdomen identifies her gender.

Say's trig female 1b

Finding the male in the next photo required an extended slow stalk. His beautiful trill, accurately described as “silvery” by Elliott and Hershberger , was well amplified by the little cluster of dead leaves where he was hiding, but difficult to locate. I coaxed him out onto the white oak leaf lobe which provides some scale, and returned him to his spot after taking his picture.

Say's trig male b

Thanks to that ventriloquial quality I had not realized in my first season of singing insects study that these trigs sing mostly up off the ground. I thought I was hearing a ground cricket. Then in my second year I encountered a bunch of Say’s trigs in the tall grasses at Blackwell Forest Preserve, took a male home so I could hear and record his song, and returned him after confirming the identification. Since then I have found them practically everywhere there is dense or tall vegetation (including my own garden!). They begin to sing in numbers in late July or early August, and continue to mid-October or November. Their trill is similar to that of Allard’s ground cricket, but the notes are more run together rather than being distinctly staccato, and usually are coming from a source above the ground. The sound quality also is different. Recordings of Say’s trig songs can be heard here  or here .

Ground Crickets

by Carl Strang

After mid-July, new singing insects make their presence known just in time to fill the silence left by the birds as they end their breeding season. Northeast Illinois’ three common species of ground crickets all have reached full tune in recent days. These are small, brown, and similar looking if you happen to see one.

Allard's 1b

The photo shows a typical ground cricket, probably Allard’s ground cricket. I photographed this one as it crossed a trail, but usually they are concealed in the grasses on the ground. Allard’s ground cricket occasionally turns up in lawns and even parking lot islands, but prefers areas with taller grasses. I hear them mainly along the edges of recreational trails in prairies and meadows. Their songs are high-pitched notes, rapidly produced at what sounds to my ear like 4-6 per second though sonagrams indicate twice that rate. I don’t call them trills because the notes don’t sound like they run together.

The common species of mowed lawns, though occurring in all sorts of grasslands, is the striped ground cricket.

Striped ground cricket 3b

This individual was flushed out by floodwaters. If you look closely you may see the stripes on the top of its head which distinguish it. The song consists of separate chirps, somewhat low pitched and unmusical (dissonant), between 2 and 3 per second. I would describe them as grating on the ear.

The third common species is the Carolina ground cricket. It would look similar to the others (microscopic features are used to distinguish specimens). Its song is very different, however, consisting of a continuous, irregularly pulsed trill that varies, with periods when more than one note comes into the song, making it dissonant. I have found it in a broad range of habitats, from wet grasslands to forest areas. It is not really a lawn species, but it often turns up around bushes and flower plantings in yards.

There are other ground crickets in our area, which I won’t detail here. Confused ground crickets occur in forests; there is a population at Fullersburg Woods Forest Preserve, for instance. Gray ground crickets occur in sandy habitats such as Lake Michigan dune areas. According to the literature there should be others in northeast Illinois, but I have not found them yet.

Though small, these crickets can be surprisingly loud. They accomplish this by finding spaces in the vegetation which act like stereo speaker cabinets, amplifying the sounds so we can hear them readily.

To hear these species’ songs, go to the Songs of Insects or Singing Insects of North America websites, via the links in the left margin of this blog. All of them sing all day, and all can be heard into November.

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