Recent Mayslake Singers

by Carl Strang

There have been a number of singing insect photo opportunities of late at Mayslake Forest Preserve. The best, just yesterday morning, was the first long-spurred meadow katydid I have found on the preserve. I could hear its quiet song, but it took a while to find it, tucked into a clump of weedy plants a few feet out from the edge of a woodland.

This angle provided just what was needed to confirm the identification, the long spurs on the cerci showing clearly.

Earlier in the week I found a round-tipped conehead singing close to the ground in a tuft of grass.

This is the most abundant coneheaded katydid in DuPage County, the latest of them to mature and the only one that sings in the afternoon as well as at night.

Last weekend, one of the families on my night hike found a narrow-winged tree cricket on the sidewalk after we finished.

The flash washed out its image a little, but the brown cap and narrow wings show clearly in this photo.

Still earlier an Allard’s ground cricket, the most abundant of Mayslake’s ground crickets, paused while crossing a trail.

Unless the autumn is severe, Allard’s will sing well into November.

Numbers of singing insects are dropping, but there still are plenty to hear this season.

Toward Singing Insect Monitoring: Dominant Frequency

by Carl Strang

When I conduct workshops or lead field trips on singing insects, people commonly ask about monitoring protocols. We have well established monitoring programs in the Chicago area for birds, frogs, butterflies, dragonflies and damselflies, plants and probably other groups I am forgetting at the moment, so how about singing insects? My answer usually revolves around the fact that different people hear singing insects differently, and this obstacle is a challenge that has yet to be solved. An important variable here is that different people hear different ranges of sound frequencies, and commonly older folks (like me) lose the ability to hear high-pitched sounds. Recently I decided to try to get a quantitative handle on this pattern, using my experience as a gauge. I went to the Singing Insects of North America website and The Songs of Insects book by Elliott and Hershberger, and lifted out the dominant frequencies sung by the species in the Chicago region.

A male short-winged meadow katydid, one of the small meadow katydids, whose song has a dominant frequency of 13 kHz.

Most singing insects produce a range of different sound frequencies when they sing, a buzz for instance consisting of a mix of many low- to high-pitched sounds. Different sounds within the mix have different energies or volumes. The dominant frequency is the loudest one in a given species’ mix. Looking at just the dominant frequency, I see that the various local species range from 1.3 to 17 kilohertz (thousands of vibrations per second, a measure of the pitch or highness/lowness of a sound). I can hear every species with a dominant frequency below 13 kHz. In fact the only species I cannot hear at all are the small meadow katydids (the members of genus Conocephalus), which sing in the 13-17 kHz range. Children and young adults can hear these, I have found. A simple, if expensive, work-around is the SongFinder device.

The long-spurred meadow katydid is my marginal species, at 12 kHz. I can hear them from close range in the woods if there aren’t a lot of competing sounds. Interesting to me is the fact that I hear them clearly at the Brookfield Zoo, where they are fairly common. I doubt that the zoo’s long-spurreds have lower dominant frequencies. My best guess is that the relative lack of other sounds in that range, plus the amplification of the songs reflecting from sidewalks and buildings, increases my ability to hear them there.

Long-spurred meadow katydid, my marginal species

Another related variable is a person’s ability to pick up a sound from a distance. Roesel’s katydid has a dominant frequency of 15 kHz. I can still hear them, but less well with each passing year, and I have to be closer to them. Children and young adults easily pick them up earlier in the song and at a much greater distance. Probably what I hear is not that dominant frequency but the lower part of the frequency range included in Roesel’s buzz. Recently I learned that young adults can hear common meadow katydids, dominant frequency 10 kHz, at a much greater distance than I can, though I hear them clearly if I am within, say, 30 feet.

Common meadow katydid

I think that monitoring protocols are possible to develop, but clearly these are variables that will need to be taken into account. There are other obstacles as well, which I will address at another time.

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.

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.

Mack Road Marsh

by Carl Strang

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

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

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

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

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

Long-spurred Meadow Katydid

by Carl Strang

Recently I spent a day at the Brookfield Zoo, which remains to this point the only place where I have found long-spurred meadow katydids in northeast Illinois.

Long-spurred 5b

The above photo is inverted; the insect was clinging to the underside of a cedar twig. This is the first individual I found two years ago. I’d noticed its song as that of a meadow katydid, but unlike other species I’d encountered. The buzz has a loose rattling quality, and the ticks that precede the buzz sound like elements of the buzz rather than the sharper ticks produced by other meadow katydids. The overall effect is that the song sounds like an accelerating buzz. I spent some time with that first individual, and managed to get some photos of his cerci.

Long-spurred 1b

The cerci are the yellow structures at the tip of his abdomen. The long inward-projecting forks of the cerci give the species its name. References indicate that long-spurred meadow katydids like cedars, but so far I have not found them in DuPage County. On my recent zoo visit I found a couple individuals singing not from cedars but from herbaceous flowerbeds. I haven’t given up on them, and continue to seek them wherever there are cedars.

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