The Tiny Ones

by Carl Strang

One of my goals this year was to achieve some clarity with two of the tiniest singing insects in the Chicago region. The variegated ground cricket (Neonemobius variegatus) and Cuban ground cricket (N. cubensis) are only a quarter to a third of an inch long. They are so unobtrusive, with their low-volume trills and hidden haunts, that you have to listen for them even to know they are around. Both species have rapid trills with crescendo starts, and unless you have perfect pitch and better hearing than me, telling their songs apart means working from sound recordings and getting technical.

Variegated ground cricket

Cuban ground cricket

My accumulated recordings of Neonemobius songs fall into two clusters, demarcated by a space that has remained remarkably consistent.

The dots in this graph each represent a recording of a Neonemobius cricket song, analyzed in the computer. The pulses represent the speed at which the cricket rubs his wings together to produce the song, and the frequency is the highness or lowness of the song’s pitch. Both measures increase with temperature. Note that variegated ground cricket songs fall into the upper left portion of the graph, Cuban ground cricket songs lower right. Dashed lines are my eyeball estimates of the space between the two clusters of points.

Variegated ground crickets vibrate their wings more slowly than Cuban ground crickets, yet have higher-pitched songs at a given temperature. This was the tentative conclusion I had drawn, but I needed some validation, and got it in October.

Here I have to back up a bit. I had found variegated ground crickets in the Chicago region, and would not have considered the possibility of Cuban ground crickets without the work of Lisa Rainsong. Cuban ground crickets had been known as a southern species until Lisa found them to be abundant in Cleveland. Her discovery alerted me to the possibility that they also might have reached the Chicago region. That possibility was realized when I found Cuban ground crickets in Gar Creek Forest Preserve in Kankakee County, Illinois. A captive Gar Creek Cuban ground cricket anchored the right-hand portion of the graph (yellow dots, yellow line).

A few observations of variegated ground crickets in previous years fell into the left-hand cluster, but I needed more. This year a captive variegated ground cricket from Gar Creek, which has both species, provided a series of recordings at various temperatures which fell as expected (red dots, red line).

Early in October I visited Lisa and her partner Wendy Partridge, and they showed me an area where Cuban ground crickets are abundant.

This meadow in the North Chagrin Reservation, a Cleveland Metroparks site, is packed with Cuban ground crickets. Lisa and Wendy check out tree crickets down the trail.

My recordings of two individuals at that site fit nicely into the previously established Cuban ground cricket cluster (green dots).

The final touch for 2018 came on October 18. I had 3 recordings, from 2006-2018, from north Blackwell Forest Preserve in DuPage County, all of which fit into the Cuban ground cricket cluster. Despite a few frosty nights, Neonemobius crickets had survived and were singing. I succeeded in flushing out one of these, and he was indeed a Cuban ground cricket. I regard this as a final validation of the graph. Now I need to go back to most of the 22 counties of the Chicago region in future years, and discover where each of these two species occurs.

Revised distribution of variegated ground crickets in the Chicago region, based mainly on analysis of sound recordings.

Revised distribution of Cuban ground crickets. One or both of the two species occur in every county, but I have not yet made sound recordings everywhere I heard Neonemobius crickets singing.

This story is an excellent example of hidden surprises that are waiting for researchers to uncover.


Singing Insects Wrap-Up

by Carl Strang

October’s cold gradually is silencing another year’s array of singing insects. In recent weeks I have made some final trips to squeeze just a little more data out of the season.

In early September I succeeded in catching an Autumn yellow-winged grasshopper with actual yellow wings (most of them in the region have had red-orange hind wings).

In early September I succeeded in catching an Autumn yellow-winged grasshopper with actual yellow wings (most of them in the region have had red-orange hind wings).

On October 5 I made a final trip up to Illinois Beach State Park, and found some stripe-faced meadow katydids still singing.

On October 5 I made a final trip up to Illinois Beach State Park, and found some stripe-faced meadow katydids still singing.

By then, of course, they had developed their full color.

By then, of course, they had developed their full color.

I was able to complete a photo series on the species with some cerci shots.

I was able to complete a photo series on the species with some cerci shots.

On October 11 I returned to Gar Creek Forest Preserve in Kankakee County and made more recordings. I did not find any more Cuban ground crickets crossing the trail, but was surprised by several variegated ground crickets doing so.

I had never before seen a variegated ground cricket, like this male, wandering in the open.

I had never before seen a variegated ground cricket, like this male, wandering in the open.

This female has an interesting pattern of pale dashes on her wings.

This female has an interesting pattern of pale dashes on her wings.

It’s reasonable to assume that they walk about at night for most of the season, but like many singing insects extend their usual nighttime activity into the day as temperatures cool. I was glad to get the visual confirmation that this species is at the site along with the (probable) Cubans.

Probably my last singing insect photo series for 2016 was of this spotted ground cricket at St. James Farm on October 18.

Probably my last singing insect photo series for 2016 was of this spotted ground cricket at St. James Farm on October 18.


Sound Ideas: Variegated and Cuban Ground Crickets

by Carl Strang

One of the highlights of the field season just past was finding variegated ground crickets, a long sought species, right under my nose, as described earlier.

Variegated ground cricket

Variegated ground cricket

Here is a recording I made in 2011 in the lawn at Mayslake Forest Preserve. I have trimmed out all but the critical end portion, which includes the abrupt end of one trill and the crescendo beginning of another:

I had made the incorrect assumption that these crickets, living in cracks and holes in the lawn, were Say’s trigs. Here is a recording of one of the trigs from nearby Fullersburg Woods Forest Preserve. The ending likewise is abrupt, but the next trill has a “chuwee” beginning.

In both cases the trills are extended, longer in the trig as a rule. A third species worth comparing here is the Cuban ground cricket. I have not encountered this species in the Chicago region, yet, but I need to be alert for it. Previously known only as a southern species, Lisa Rainsong has found it to be common in the Cleveland area. Ecologically it seems to resemble the variegated ground cricket in liking wet areas near lakes, rivers, and marshes, but is active on the surface rather than remaining out of sight in gravel or in soil crevices. Here is a partial recording of a Cuban ground cricket living in a terrarium in Lisa’s home:

The repeated brief scratches or chirps are from a striped ground cricket in another terrarium. The Cuban ground cricket, a member of the same genus as the variegated, likewise has a crescendo beginning, an extended high-pitched trill, and an abrupt ending. The pitch is just a little lower than that of the variegated, but otherwise they are much the same.

A final note on this topic is that my analysis allowed me to identify a recording from Illinois Beach State Park as belonging to a variegated ground cricket.

The singer was located beneath this vegetation, a few steps from the Dead River. I could not find it, and now realize that it must have been beneath the surface.

The singer was located beneath this vegetation, a few steps from the Dead River. I could not find it, and now realize that it must have been beneath the surface.

Here is an excerpt from the recording (you may need to turn up the volume):

All of this has me primed to document variegated ground crickets elsewhere in the coming season, and to be alert for Cuban ground crickets.


Sometimes It Gets Messy

by Carl Strang

I haven’t been posting here lately, as I have been busy writing summaries and reports on the past season of my singing insects study. As 2014 was a good, productive year, this has been a time consuming process. The discovery of variegated ground crickets in October brought a new complication, as their song superficially resembles those of several other crickets, including Say’s trig and a few other ground crickets. I decided to review all of my relevant recordings and re-analyze them to discover distinguishing features. Two quantities that researchers have discovered to be significant in singing insects are dominant frequency (pitch or highness of the tone) and pulse rate (the speed at which wings open and close to produce the song). These are determined by sonographic analysis of the recordings in the computer. The plot of all the recordings looks like this:

Hence “messy” in this post’s title.

Hence “messy” in this post’s title.

The colors represent my decision as to species (usually I did not see the singer): red for Say’s trig, green for variegated ground cricket, blue for gray ground cricket, black for sphagnum ground cricket, and yellow for Cuban ground cricket. The shapes represent one of three ways in which these crickets begin their songs: square for an abrupt start (or for unknowns, cases in which the recording did not include the start of a trill), triangle for a crescendo from low volume to the extended peak of loudness, and circle for a start that often is rendered “chuwee.” The last has an abrupt beginning, but immediately has a momentary drop in pitch or volume that as quickly is followed by the continuous, full volume trill. All these crickets end their trills abruptly. Empty centered shapes are for recordings that were noisy or in which more than one individual was singing, potentially leading to a false reading. The numbers are the temperatures in degrees Fahrenheit, when known.

Ideally, there would be well defined clusters of points separating the represented species. This did not happen, and I can identify a few reasons. In some cases, the recording’s quality was compromised (the hollow-centered shapes). Temperature can affect song qualities, and there is no single established threshold for all species, below which recordings become ambiguous. Also, some features of songs are not in the graph, notably the length of trills, and the length of pauses between them.

The outlier for variegated ground crickets, the green triangle with the lower frequency and pulse rate, was the recording I made indoors. I only kept that cricket for one night, and had it in a cage with only a few leaves on its floor. I have more trust in the values for the Cuban ground cricket, which was well established in a beautifully furnished terrarium at Lisa Rainsong’s home in the Cleveland suburbs, where I stopped briefly on my way to my brother’s for Thanksgiving (thanks again, Lisa!).

Here are my tentative conclusions from this analysis:

First, I need to make a lot more recordings, with care to note habitat, temperature, and whether the singer is on the ground or height above the ground. I need to isolate one singer from all others, with the microphone as close to it as possible. Better habitat conditions are needed to get good response for indoor recordings.

So far, dominant frequency, habitat, and how the trill starts are more helpful than pulse rate in distinguishing these species.

Say’s trig songs are characterized by a chuwee start, a location above the ground, and a lower pitch (usually 7.5kHz or less). Trills may be long or short, but when short usually are in rhythmic bouts.

Variegated ground crickets consistently have crescendo starts, trills usually less than a minute long, and pauses between of at least several seconds. Field recordings had high dominant frequencies (8.6 kHz or above).

One Cuban ground cricket recorded indoors had a pattern like that of the variegated, but a lower dominant frequency (7.6 kHz). From Lisa’s description, these two species occur in very similar habitats, but the Cuban ground cricket is more likely to be found on the surface of the ground. Variegateds occupy soil cracks or other buried locations.

Gray ground crickets have abrupt starts and only brief-moment pauses, with dominant frequencies of 8.0-8.9 kHz. They occur in dry sand soils.

One recording of a sphagnum ground cricket has a high dominant frequency (8.5 kHz), plus a chuwee start. It occurs only in sphagnum bogs, but potential associates include Say’s trig and variegated ground cricket, which can be distinguished, respectively, by their lower dominant frequency and crescendo starts.

That’s enough for now. I plan to share some of these recordings in future posts.

How to Title This?

by Carl Strang

I debated what tack to take with this post. There are plenty of possibilities. I could have titled it “Two Problems Solved at Once.” Another possibility was “Well, THAT’s Embarrassing.” Then there’s the old standby, “Another Lesson Learned.” “One More Gift from This Field Season” would have had a more positive twist. I even considered “Tastes Like Chicken,” but that’s too tangential. Maybe I should just tell the story.

The roots of this tale go back in two directions, previously introduced in this blog. One had the title, ironic now, of “A Small Mystery Solved.” In it I described how I had tracked certain long cricket trills to cracks and earthworm holes in shaded portions of the mansion lawn at Mayslake Forest Preserve. Though I didn’t see the crickets, and the match wasn’t perfect, the songs sounded close enough to those of Say’s trigs for me to conclude that they were the singing species, even though they otherwise, in the literature and in my experience, are known as a species that lives in vegetation up off the ground.

To my credit I held onto some skepticism toward this conclusion, and was planning to set pit traps at some point to try and catch one of these crickets. Then an unexpected opportunity appeared. During my lunchtime walk on Tuesday I noticed that small bunches of dried leaves that had collected along the curb were harboring some of these singers. I began pulling out leaves so as to expose what I expected would prove to be Say’s trigs. The songs certainly sounded like those of that species. Crickets began to jump out, mostly tiny immatures, and then I flushed a larger one. It manically jumped away. It was light brown, like a Say’s trig, but not totally so, and I wasn’t able to get a clear view. I tried again, and ultimately one sat still for a photo.

This was not a trig, but a ground cricket.

This was not a trig, but a ground cricket.

That one escaped, but I finally caught another, unfortunately damaging him. I was going to need to collect one, anyway, as ground crickets are one of the most difficult groups to identify. I went through the keys in the Singing Insects of North America website, and placed this cricket in the genus Neonemobius. I leafed through the species pages, and ultimately found a match, right down to the pale palps and the head that was light brown on top but dark brown or black in front.

Could they be variegated ground crickets?

Could they be variegated ground crickets?

That brings me to the other root of this story. The variegated ground cricket’s mapped range encompasses the Chicago area, but information about the species in the literature is limited and anecdotal. Prior to Tuesday there was only one northern Illinois record. The most common theme is that they occur among the pebbles at the edges of streams. I have made a few trips trying to find them (one chronicled here, plus two journeys to Kankakee River State Park), always without success.

So the joke’s on me. For years I have been working right next to a sizeable population of variegated ground crickets without realizing it. I have searched in several counties for them, only to find them literally in my back yard. But what about that “Tastes Like Chicken” title? This is not the only cricket whose song sounds to my ear like that of Say’s trig. There also is the spring trig, which indeed lives close to the ground. The melodious ground cricket’s song is not too far off, though the two are readily distinguished by an experienced ear. From now on I need to be suspicious whenever I think I am hearing a Say’s trig. A moist lawn is far removed from a pebbly stream bank, so with that kind of ecological range I expect to find variegated ground crickets in many more places. I am making recordings, and sometime in the coming winter I will attempt to find a way to distinguish the variegated ground cricket’s song. I will share the results here.

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.

Search for Variegated Ground Cricket

by Carl Strang

The variegated ground cricket, Neonemobius variegatus, has been an intriguing presence on the “possibles” list of northeastern Illinois singing insects. Though its range map at the Singing Insects of North America website (SINA) includes our region, essentially nothing else about the species was there until the recent addition of a photo. Last year I stumbled across some information on the Internet that partly explained the lack of information.

The recognition of this species began as a Nebraska specimen named Cyrtoxyphus variegatus. Hebard in his revision of ground crickets (1913. Proc. Acad. Nat. Sci. Philadelphia 65:394-492) placed it in subgenus Neonemobius and re-named it Nemobius bruneri. He mentioned that it occurred in Kansas and Indiana as well, and described it as having a striking dotted speckled appearance. Hebard identified specimens collected from pebbles and stones along the Oletangy River at Columbus, Ohio, but in his 1934 monograph on Illinois Orthoptera placed all its locations in the southern part of our state. Another publication, reviewing North Carolina singing insects, describes a similar habitat (gravel beds and sandy stream banks, not in thick woods), mentions it is a late summer and fall species, and describes its song as being a continuous unbroken trill, high pitched and weak, lacking pulses and produced day and night. In 2010 I sought it without success in the rocky edges of Sawmill Creek at Waterfall Glen Forest Preserve.

The map at SINA suggested that they are in Ogle County, so I headed to the Rock River on Tuesday. Among my stops was this one at Castle Rock State Park.

This was fractured stone rather than gravel, though there was plenty of sand mixed in along the shore.

The picture in my mind of variegated ground cricket habitat was matched perfectly by this site at Oregon.

Nice round gravel covers a large area of shore.

In these locations I listened with my ears alone and with the SongFinder, walked over the entire area scanning carefully, kicked gravel, turned over lots of stones.

In my mind they should be here.

Nothing. The optimist in me describes this trip as successful. I succeeded in discovering one way not to find variegated ground crickets. I’m not sure what my next step will be. I plan to head down toward the Kankakee River in the next week or two. Maybe I’ll find them there.

Waterfall Glen Woodlands

by Carl Strang

Waterfall Glen is DuPage County’s most biologically diverse forest preserve. It has the greatest topographic variety, the greatest geological variety, the greatest mix of plant communities, covers hundreds of acres and therefore harbors more species than any other preserve. I had a few specific places I wanted to check for singing insects on my most recent visit there, and will need two posts to describe that afternoon sensibly. My first stop was Sawmill Creek.

In particular I hoped to find variegated ground crickets there. I hadn’t noticed any unusual songs along that stream before, for instance during the Roger Raccoon Club’s creek walks, but I hadn’t known then that the variegated ground cricket is a habitat specialist found on pebbly or sandy stream edges. In DuPage County, covered with tens to hundreds of feet of clay-rich glacial till, the one stream most likely to match this habitat description was Sawmill Creek, which has pebbly banks and in places flows right over the exposed Silurian dolomite bedrock. I struck out, though. I heard no trilling species other than Say’s trigs and Carolina ground crickets, even with the SongFinder, and so my tentative conclusion is that this little-studied ground cricket lives elsewhere than DuPage County.

Next I checked out low wet areas in the western part of Waterfall Glen’s forest, some reduced to muddy patches and others still ponded at this point in the season.

Here I was listening for two other ground cricket species, the spotted and sphagnum ground crickets. The latter was the longest shot, as there was no sphagnum moss, but sometimes species have a broader habitat range than the literature suggests. This time, though, I heard no new species in that part of the forest.

As I followed the trail back to my car I got one very good break, however. I heard a meadow katydid’s buzzing song coming from the edge of the woods about 20 feet away. It wasn’t as loud as a black-legged meadow katydid, and anyway the habitat was high and dry. As I approached the singer I realized I recognized the song. Sure enough, it was a long-spurred meadow katydid.

The long pointy teeth on the cerci confirmed the ID.

This finding was a source of great relief. A few posts ago I mentioned that my failure to hear some of these singing at Blackwell Forest Preserve (except when I wore the SongFinder) had me wondering if my hearing was failing rapidly. Such clearly is not the case. So, what was going on at Blackwell? At some point I’ll have to see if I can find out. Incidentally, at both the Blackwell and the Waterfall Glen locations for long-spurreds there were no coniferous plants present, so here is one of those examples of hints in the literature being misleading.

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