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.

Memorial Weekend Miscellany

by Carl Strang

As Gary and I toured wild places around Culver over the weekend, we found more of interest than sulfur-winged grasshoppers.

Many wildflowers were blooming, including lance-leaved violets at the Winamac State Fish and Wildlife Area.

Many wildflowers were blooming, including lance-leaved violets at the Winamac State Fish and Wildlife Area.

A number of rapids clubtails worked the sandy power line corridor at Memorial Forest.

A number of rapids clubtails worked the sandy power line corridor at Memorial Forest.

One sad note was a road-killed otter.

I had heard that otters have returned to the Tippecanoe River. This one climbed a tributary to reach the Maxinkuckee Wetlands, and became a casualty.

I had heard that otters have returned to the Tippecanoe River. This one climbed a tributary to reach the Maxinkuckee Wetlands, and became a casualty.

No photo to show for it, but we were impressed by astronomical observations as well. While sampling the variety of Hoosier beers Gary had brought up from Indianapolis, we checked out Mars and Saturn through the spotting scope. Mars, as close as it ever gets to Earth, was a reddish disk. Much farther away, Saturn appeared as a cute little image with the rings nicely visible and separate from the planet’s main mass.

We closed the weekend by attending the local VFW Memorial Day ceremony, and visited the graves of our parents, who passed away two years ago. Then we went our separate ways home.

Northern Wood Crickets

by Carl Strang

Those of you on the mailing list for my annually updated guide to the singing insects of the Chicago region would look in vain for northern wood crickets in last year’s edition. I simply wasn’t aware that they could be here. While preparing for the Hills of Gold bioblitz, however, I found that their range extends into our region. I had not included them in the hypothetical list because initially it was directed toward DuPage County in Illinois, and wood crickets never have been found in northeastern Illinois. I gained some experience with wood crickets in the bioblitz, and the sound recordings I made there proved to be of the northern wood cricket, Gryllus vernalis. Study of the relevant scientific paper (Yikweon Jang and H. Carl Gerhardt. 2006. Divergence in the callling songs between sympatric and allopatric populations of the southern wood cricket Gryllus fultoni [Orthoptera: Gryllidae]. J. Evol. Biol. 19: 459–472) indicated that the 2-chirp-per-second, 3-pulse-per-chirp, songs coming from leaf litter in forest habitat, were of northern wood crickets. Southern wood crickets, the other possibility, would have had faster chirps at that temperature.

Last week’s vacation survey trips went so well, despite two days lost to rain, that I had Saturday available to seek northern wood crickets the Indiana portion of the Chicago region (I had not found them in the Illinois, Wisconsin or Michigan excursions). My first two stops, in St. Joseph County’s Bendix Woods and Fulton County’s Judy Burton Nature Preserve, were fruitless. Mid-afternoon brought me to the Winamac State Fish and Wildlife Area in Pulaski County, and I drove the gravel roads until I found one of the parking lots in a forested spot. Immediately I heard the chirps of Gryllus crickets, and I dug out the Marantz sound recorder. As I recorded two different crickets I believed I was hearing 3 pulses in the chirps, as had been the case at the bioblitz.

This was where the cricket in the recording shared below was located.

This was where the cricket in the recording shared below was located.

I would have liked to try and flush out one of the singers, but as the photoflash lighting in the photo suggests, it was getting dark fast, and I barely reached the car before the downpour hit. I tried to get around the storm by driving to the Jasper-Pulaski Fish and Wildlife area, but no dice, and I had to call it a day. So, here is a cut of the stronger recording:

Can you distinguish the 3 pulses that form each chirp?

The visual rendition of the recording clearly shows the 3-pulse chirps, but they are being produced at a 4-chirp-per-second rate.

The visual rendition of the recording clearly shows the 3-pulse chirps, but they are being produced at a 4-chirp-per-second rate.

This might have been confusing, given that the southern wood cricket, not yet known from northern Indiana, more typically has a 4-chirp rate, but the soil temperature was very warm, at nearly 80F, and the scatter for vernalis in Jang and Gerhardt’s graph extends to 4 chirps at that temperature. Also, the dominant frequency was 5.9kHz, good for vernalis but pitched way too high for fultoni at any temperature. So, I am content for now that I have established a present-day northern wood cricket presence in the region. One goal for next year will be to seek them in more locations, make more recordings, and get a better sense of their song features in this part of their range.

Scouting Fulton and Pulaski

by Carl Strang

When I updated my regional guide to singing insects over the winter, I decided to add range maps. This was a little premature, because I barely have begun the survey work, but I also had sources in the scientific literature to augment my own observations.

Here is a page from the guide. The map shows the counties I decided to include in a region centered in northeast Illinois and northwest Indiana, but extending a little into Wisconsin and Michigan. Black dots are recent observations, open ones are from the literature, which often goes back more than 5 decades.

Here is a page from the guide. The map shows the counties I decided to include in a region centered in northeast Illinois and northwest Indiana, but extending a little into Wisconsin and Michigan. Black dots are recent observations, open ones are from the literature, which often goes back more than 5 decades.

Another winter project then became to identify sites in all the counties where I could focus my survey efforts, mainly state parks and other public properties. The plan is to start visiting them this year, noting species I can identify through sight and hearing without collecting. If collecting seems necessary, I can seek permits in a future year, but there will be plenty to do without going to all that trouble yet.

Over the weekend I visited sites in Fulton and Pulaski Counties, Indiana, which are the empty counties in the snowy tree cricket map at the eastern end of the bottom row. In Fulton County I had decided to focus on the area around Lake Manitou at Rochester. This proved to be a good choice, as there appear to be representative habitats of nearly every type.

The Judy Burton state nature preserve, for instance, has extensive meadows undergoing prairie restoration, and woodlands, all with maintained trails.

The Judy Burton state nature preserve, for instance, has extensive meadows undergoing prairie restoration, and woodlands, all with maintained trails.

It is early in the season, but I was able to add county records for the green-striped grasshopper and spring trig.

Pulaski County boasts the Tippecanoe River State Park and Winamac Fish and Wildlife Area. The state park is almost entirely forested, so I didn’t spend much time there (early singing insect action is in the meadows and prairies), but it will be great later in the year. The fish and wildlife area has a more diverse array of habitats.

This weedy field had many displaying green-striped grasshoppers and a few spring field crickets, both of which I now can add to the maps.

This weedy field had many displaying green-striped grasshoppers and a few spring field crickets, both of which I now can add to the maps.

This grasshopper, photographed in the above field, appears to be a species of Melanoplus, and so not a singing insect.

This grasshopper, photographed in the above field, appears to be a species of Melanoplus, and so not a singing insect.

As time permits, I will be returning to these areas later in the season. I am looking forward to making the acquaintance of many places in the region’s other counties, as well.

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