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.

 

Making a Case 3: Northern Wood Cricket

by Carl Strang

Last year I concluded that I had found northern wood crickets (Gryllus vernalis) in the Winamac State Fish & Wildlife Area in Pulaski County on June 13, based on habitat and sound recordings. In 2016 I returned to that site on May 29, but did not find them singing. On June 3 I heard Gryllus crickets chirping along the Marquette Trail, near the east border of Lake County, Indiana. All were in forest or savanna areas, the singers in deeply layered black oak leaves, usually in shade under black oak trees but some in isolated collections of leaves surrounded by sand.

One of the woodland crickets’ song sites near the Marquette Trail.

One of the woodland crickets’ song sites near the Marquette Trail.

None were in the open grassy areas favored by spring field crickets (G. veletis), even though such habitat was close by. I recorded two of these individuals, and later in the season recorded field crickets in meadow and prairie habitats favored by veletis but where vernalis would not be expected, plus another individual that by habitat should be vernalis, at the Kankakee Sands site in Kankakee County, Illinois.

The results seemed contrary to what would be expected from previous studies.

The likely vernalis (forest) had lower chirp rates than likely veletis (grassland).

The likely vernalis (forest) had lower chirp rates than likely veletis (grassland).

The number of pulses per chirp was unhelpful, with likely veletis ranging 2-4, likely vernalis 3-4. Linear regressions of the two sets of data show, perhaps significantly, the same slopes of chirp rate increase with temperature (physiology of closely related species expected to show a similar response to temperature). The linear regressions indicate that, for a given temperature, forest cricket chirp rates are 1.44/second less than grassland chirp rates. All data I can find in the literature for vernalis were collected from that part of their range where they are sympatric with the southern wood cricket (G. fultoni). Jang and Gerhardt (2005. J. Evol. Biol. 19:459–472) found that fultoni song characteristics differed between populations sympatric with vernalis and those allopatric to that species. They did not study allopatric vernalis. As my recordings may be the only ones that have been made where vernalis is allopatric to fultoni, and given the clear difference between recordings in habitats for likely vernalis and likely veletis described above, so far it appears that habitat, chirp rates and temperatures will be enough to establish the presence of vernalis. The major obstacle to finalizing this conclusion is confirming the identity of the forest crickets. So far I have been unsuccessful in efforts to catch or even see one. Next year I need to continue making recordings and trying to catch and measure suspected northern wood crickets.

Making a Case 2: Prairie Meadow Katydid

by Carl Strang

After more than ten years of study, I still have not found several species of singing insects that historically were known in the Chicago region. One of these was the prairie meadow katydid, one of the smaller members of its group. On August 16, Wendy Partridge and I were checking out the bike trail near the nature center at Illinois Beach State Park. Through the SongFinder, which allows me to hear high pitches, I heard faint rapid ticking sounds which, when heard from a closer position, resolved into brief buzzes. They were mechanical and katydid-like rather than cricket-like in quality, and didn’t match anything I had heard before. Wendy, with her unusually good hearing, barely could pick them up. Later, checking reference recordings, I decided they fit the song of the prairie meadow katydid. They were not in the habitat I would expect, however, being in dense vegetation where grasses were mixed with woody plants and forbs, generally shaded. That katydid species has been known to occur in that park, however.

Then on September 27 I caught and photographed a small female meadow katydid in a relatively dry portion of the Gensburg Prairie in Cook County.

Posterior portion of the Gensburg Prairie female.

Posterior portion of the Gensburg Prairie female.

Her color didn’t seem quite right for a short-winged meadow katydid, which is a common species at that site especially in the wetter portions. Studying the photos, and looking back at references, I have decided that she was a prairie meadow katydid. Along the way I looked back at all my photos of short-winged meadow katydids, and found two other individuals that met at least some of the criteria for prairie meadow katydid, one in 2011 at Mayslake Forest Preserve, and one in 2014 in the savanna woodland at Illinois Beach State Park.

The Mayslake female

The Mayslake female

The Illinois Beach State Park female

The Illinois Beach State Park female

All three have curved ovipositors that are slenderer in proportion than in a typical short-winged meadow katydid.

Typical female short-winged meadow katydid

Typical female short-winged meadow katydid

All three also have femoral patterns in which there is a lengthwise pair of lines, as in the short-winged, but have ladders of narrow crossbars rather than being clear between them as in typical short-winged. There is enough overlap in body length, according to references, that it is not a consideration in comparing those two species. The ovipositors are too short, and the femur patterns wrong, for straight-lanced meadow katydid to be a consideration. The Mayslake female is different from the other two individuals in three possibly significant ways: the femoral ground color is green rather than brown or tan, the wings are much longer, and the front of the head does not appear to rise so much (this last being a difference mentioned by W.S. Blatchley in his classic Orthoptera of Northeastern North America, which gives unusually detailed descriptions of species).

Anterior portion of the Gensburg Prairie female. Note the abrupt rise of the tip of the head when viewed from the side.

Anterior portion of the Gensburg Prairie female. Note the abrupt rise of the tip of the head when viewed from the side.

Dorsal view of the Gensburg Prairie female. Blatchley describes the wings of prairie females as covering only one-fourth of the abdomen, two-thirds in short-winged females. Furthermore, the tip of the head, when viewed from above, is relatively wide after an inward bending of its sides, expected from Blatchley’s description.

Dorsal view of the Gensburg Prairie female. Blatchley describes the wings of prairie females as covering only one-fourth of the abdomen, two-thirds in short-winged females. Furthermore, the tip of the head, when viewed from above, is relatively wide after an inward bending of its sides, expected from Blatchley’s description.

Compare this common meadow katydid, with its relatively narrow and straight-sided tip of the head, to the previous.

Compare this short-winged meadow katydid, with its relatively narrow and straight-sided tip of the head, to the previous.

 

Side view of the same male as in the previous photo. Again, note the lack of a rise in the top of the head profile.

Side view of the same male as in the previous photo. Again, note the lack of a rise in the top of the head profile.

Blatchley also believed that prairie meadow katydids occur only in “raw prairie,” a description which applies to Gensburg and Illinois Beach but not to Mayslake. I am inclined to regard the Mayslake individual as an anomalous short-winged meadow katydid, but pending study of museum specimens, am naming the other two prairie meadow katydids.

Making a Case 1: Cuban Ground Cricket

by Carl Strang

There is a part of me that likes to keep things simple. There is another part that loves diversity and complexity. Today’s story touches on both those aspects, and features two species, the variegated ground cricket and the Cuban ground cricket. Variegated ground crickets are not well represented in the scientific literature, I think because they seldom come out of their refuges in the soil and have unobtrusive songs. Once I gained experience with them at Mayslake Forest Preserve a few years ago in a happy accident, I began to find them elsewhere, ultimately in every one of the 22 counties in my survey area.

The mix of colors and patterns on the head, in particular, give the variegated ground cricket its name.

The mix of colors and patterns on the head, in particular, give the variegated ground cricket its name.

At roughly the same time, Lisa Rainsong found Cuban ground crickets in the Cleveland area, far north of their previously known range. They are better studied in general, because they are inclined to wander on the surface of the ground. Both of these species are in the same genus, and both have similar songs, long trills that emerge from crescendo starts. Lisa came out to my area in 2014 and made recordings that seemed to establish that variegated ground crickets but not Cuban ground crickets indeed were what I had been finding. That satisfied my simplicity loving side.

Then came September 15 of this year. I was walking the upper trail at Gar Creek Forest Preserve, just south of Kankakee and near the southern edge of my survey region, in a shaded wooded spot adjacent to a ditch in which water was flowing. I noticed a tiny cricket crawling across the trail. Thinking this might be a rare opportunity to photograph a variegated ground cricket out in the open, I got down low and took a series of photos. This was not a variegated ground cricket.

The male was largely black.

The male was largely black.

His head was black, the palps white with black end segments.

His head was black, the palps white with black end segments.

The only songs I was hearing nearby belonged to tinkling ground crickets and what I would have called variegated ground crickets. I made a recording of one of the latter, and farther down the trail toward the Kankakee River recorded another. The two recordings contrasted, the first with a dominant frequency of 8.06 kHz and 53 pulses per second, the second with a higher pitch and lower pulse rate, 8.6 kHz and 38 p/s respectively. The latter fits variegated ground cricket well. The former has the pulse rate of a Cuban ground cricket but the frequency is higher than the 7.0-7.5 range that is typical for that species.

I returned on September 26. It was a very windy afternoon, so singers were difficult to locate and isolate, but I was able to made recordings in the area where I found the suspect cricket. Again there seemed to be two categories of songs, lower pitch with higher pulse rate on the one hand (7.9/52, 7.5/signal not strong enough to read pulse rate), higher pitch plus lower pulse rate on the other (8.2/35, 8.2/34, 8.4/signal not strong enough to read pulse rate).

I found another male wandering on the trail, caught him, chilled him, and took photos against a backdrop for measurement, and upside down to check tibal spurs. The body length of 8mm and what appeared to be uneven tibial spurs seem to confirm that this ground cricket is in genus Neonemobius.

The tibial spurs are the short ones in the center of the photo; the lower one looks longer than the upper one.

The tibial spurs are the short ones in the center of the photo; the lower one looks longer than the upper one.

The only black members of the genus in the eastern U.S. are the sphagnum ground cricket and Cuban ground cricket. Only the Cuban fits this habitat.

I did not have a collecting permit for that site, so I had to release the cricket. Next year I hope to have a permit which will allow me to take one of these crickets home for sound recordings and, ultimately, to provide a voucher specimen which may be a first record of Cuban ground cricket for the state of Illinois if I am right in my identification.

So the story has become more complicated, which satisfies my diversity loving side.

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