Sound Ideas: 3 Ground Crickets

by Carl Strang

Today I share recordings of 3 ground crickets. The first of these, the melodious ground cricket, is not very well studied, and recordings of its song are not commonly available.

Melodious ground cricket

Melodious ground cricket

The song is a fairly loud, steady trill with a pleasant tone:

That song is most like that of Say’s trig, which can occur in close proximity as both are wetland species. When such is the case, the distinction is clear. Here is a recording of Say’s trig for comparison:

The recordings are a little misleading in that both species can be equally loud. Next up is the sphagnum ground cricket.

Sphagnum ground cricket. This species does not occur away from sphagnum moss.

Sphagnum ground cricket. This species does not occur away from sphagnum moss.

The song is higher pitched and more rapid than that of Say’s trig, which again often co-occurs.

The final species has an interrupted trill, unlike the continuous singing of the previous crickets. The confused ground cricket usually is found in drier portions of woodlands than the more swamp-dwelling melodious ground cricket.

Confused ground cricket

Confused ground cricket

The song is about one second on, one second off. If there are few other sounds, you may hear some stuttering during the “off” intervals:

 

Singing Insects Guide Updated

by Carl Strang

Each year I update my guide to the singing insects of the Chicago region. This year’s pdf edition is up to 3.5mb, with the addition of a number of new species pages and corresponding reduction in the hypotheticals section.

Cover

Cover

If you are not on the mailing list and wish to receive a free copy, send an e-mail request to my work address, cstrang@dupageforest.org

 

Sound Ideas: Three Meadow Katydids

by Carl Strang

Today I am sharing recordings of 3 species of large meadow katydids (genus Orchelimum). One way or another their songs all fit the ticks-and-buzz pattern characteristic of their group. I will order them idiosyncratically, by how well I can hear them in the field. I will be interested in any comments on how well you can hear them in these recordings. The first is our most common species in the genus, the black-legged meadow katydid O. nigripes.

Black-legged meadow katydid

Black-legged meadow katydid

This was a very warm individual who was rushing the ticks. I render the pattern tickety-buzz, as there usually are 3 ticks leading directly into the buzz, with a brief pause before the next set. This species usually can be found in or near wetlands. I can hear its song unaided without any trouble.

Next up is the long-spurred meadow katydid, O. silvaticum.

Long-spurred meadow katydid

Long-spurred meadow katydid

Here the ticks have much the same quality as the buzz, several very brief rattles that merge into the rattling buzz. This is a katydid of woods edges and adjacent areas with tall herbaceous vegetation. I can hear some of these unaided in the field, on a calm day without other competing sounds, or when there are plenty of reflecting surfaces, but usually I need the SongFinder pitch-reducing device to detect them. I can hear this recording clearly, though.

Finally, here is a species I first encountered this past season, the stripe-faced meadow katydid, O. concinnum. It is a specialist in certain kinds of wetlands, and is much less common than the others.

Stripe-faced meadow katydid

Stripe-faced meadow katydid

This one I can’t hear at all from more than a few feet away, and I can barely hear it in this recording. I really need the SongFinder for this species. The ticks are more numerous, more separated, and more irregularly spaced, than in the black-leg.

Sound Ideas: Japanese Burrowing Cricket

by Carl Strang

One of the unexpected findings from the field season just past was the discovery of Japanese burrowing crickets at Bendix Woods in St. Joseph County, Indiana.

Japanese burrowing cricket

Japanese burrowing cricket

As described earlier, there is a well-established population of this exotic species in the gravel-filled medians dividing parking lots and drives in the central part of the park. They are well buried, and it was only their distinctive songs that gave them away.

The chirps are distinctly buzzier than those of the fall field crickets that were singing nearby. Here is a fall field cricket recording from 2006 for comparison.

Listening to it, I’m getting a warm reminder of summer. Common true katydids, a striped ground cricket, and wall-of-sound tree crickets and other ground crickets are in the background.

 

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.

 

Museum Encounter

by Carl Strang

One of my responsibilities is to curate the Forest Preserve District of DuPage County’s natural history collection. Recently I was cataloguing some drawers of insect specimens when I noticed two tree crickets that had been collected in Wheaton a couple of decades ago, but had not been identified. These proved to be a pair of Davis’s tree crickets, a species I have heard singing in several locations but never have seen, as they generally remain high up in the tree canopies.

In dorsal views these appear to be rather generic, as tree crickets go.

In dorsal views these appear to be rather generic, as tree crickets go.

However, under the magnifying glass the basal antenna segments prove them to be Davis’s. Each segment shows a single straight black line. It would be curved or hooked in the narrow-winged tree cricket, or there would be an additional spot if this were one of the meadow-dwelling species.

However, under the magnifying glass the basal antenna segments prove them to be Davis’s. Each segment shows a single straight black line. It would be curved or hooked in the narrow-winged tree cricket, or there would be an additional spot if this were one of the meadow-dwelling species.

This was a reminder of the value of museum collections. Though I seldom collect specimens in my singing insects survey, that is because it seldom is necessary. For the most part, insect songs are distinctive, and if anything are more so than their physical characteristics. Because the insects distinguish themselves by sound, selective pressure on visual features is relatively weak. Sibling species pairs and groups can be found in most major singing insect categories. For example, the Tibicen cicadas closely resemble one another, as do the coneheaded katydids, the ground crickets, the field crickets, many of the meadow katydids, the bush katydids and, as in the present example, many of the tree crickets.

That said, I take voucher specimens in the rare circumstances when songs don’t tell enough of the story, and preserve specimens that I inadvertently damage when handling them to confirm identifications.

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.

The Cricket Double Wave

by Carl Strang

This is the time of year when the singing insect season is nearly done, with only the last song dates to note for the few rugged species still singing. I have been writing my annual research summary, and one data set recently completed was my Fermilab field cricket count. In the warm months I take bike rides through Fermilab, a U.S. Department of Energy research site, on roughly a weekly basis. I count the number of singing crickets I hear. The resulting graph has a double wave shape.

Counts of singing field crickets heard during bicycle rides following a standard route through Fermilab.

Counts of singing field crickets heard during bicycle rides following a standard route through Fermilab.

Two species are represented here, the spring field cricket and the fall field cricket. Their songs are identical to the ear. The graph shows that spring field cricket counts increased rapidly from the first appearance on May 18 to a peak in mid-June, then rapidly fell. There never was a time when fewer than 50 crickets were counted in July, probably indicating overlap between the two species, with the last spring field crickets continuing into the last half of that month. Fall field cricket numbers built rapidly to a peak in the first half of September, and exceeded the maximum count for spring field crickets in the same area, before dropping rapidly in early October.

 

A Last Hurrah, Maybe

by Carl Strang

A field excursion for singing insects took me back to Indiana on Friday. The sky was clear in the morning, with the temperature in the upper 50’s F, but conditions deteriorated back to October wind and clouds through the afternoon. As I drove back home I had the feeling that, except for noting last song dates for species I encounter while engaged in other activities, the 2014 field season is done. Nevertheless, I had picked up another 6 county records, bringing the year’s total to 101.

This female fork-tailed bush katydid was my first of that species for Pulaski County.

This female fork-tailed bush katydid was my first of that species for Pulaski County.

The kinked shape of the ovipositor’s dorsal edge, along with the insect’s small size, assured the identification. Note the teeth around the tip, used when cutting into plant tissue for egg laying.

The kinked shape of the ovipositor’s dorsal edge, along with the insect’s small size, assured the identification. Note the teeth around the tip, used when cutting into plant tissue for egg laying.

 

Jumping Bush Cricket Advances

by Carl Strang

The jumping bush cricket is the singing insect species that is shifting its range boundary most rapidly to the north in the Chicago region.

Jumping bush cricket

Jumping bush cricket

This one is worth following annually, and a couple weeks ago I made a few evening drives to find how far they have advanced this year.

Here is the resulting map, on the scale of the 22-county area I am surveying for singing insects. Black dots represent counties in which I have found the species as of last year. Red stars mark the northern extent in 2013, yellow ones 2014.

Here is the resulting map, on the scale of the 22-county area I am surveying for singing insects. Black dots represent counties in which I have found the species as of last year. Red stars mark the northern extent in 2013, yellow ones 2014.

The four yellow stars are in four stream corridors that the crickets sometimes follow. I did not do this check along the West Branch of the DuPage River last year. As you can see, there was a measurable hop north. For the first time I found them in Kane County; they were just south of there in Kendall last year. Also, now they have extended into northern Cook County both along Salt Creek and the Des Plaines River. These new locations represent about a half-mile northward shift, and I will be interested in finding whether they maintain that rate next year.

 

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