Even More Melodious

by Carl Strang

Relatively little has been published about melodious ground crickets (Eunemobius melodius). These tiny insects with their beautiful trilling songs first revealed themselves to me at Indiana Dunes State Park in 2012.

Melodious ground cricket

They were abundant in an open, low wet forest associated with the shrub swamp that occupies a central position within that park. The ground there has relatively little vegetation beneath the trees, with abundant rotting logs on the ground, mosses, ferns, and some other vascular plants, but much ground with nothing but wet leaf litter. On another day, I heard a few melodious ground crickets in a similar habitat at Warren Woods in Berrien County, Michigan, and in a shrub swamp in Warren Dunes State Park, also in Berrien. There the matter rested until I heard a single individual in a bottomland forest in Tippecanoe River State Park, Pulaski County, Indiana, late last year. That observation planted an idea: perhaps this species is more abundant than I realized. Flood plain forests, resembling that original site at Indiana Dunes State Park, can be found along all the major rivers in the Chicago Region. Could melodious ground crickets be found in all those places? That set the stage for one of this year’s goals.

I first tested the idea on August 11 at the Momence Wetlands, a state-owned property in Kankakee County, Illinois. As I walked into this Kankakee River floodplain forest, I was struck by its similarity to other places where I have found melodious ground crickets, and before long I began to hear them singing. As I have come to expect, they were on the ground, in or close to rotting logs. I made sound recordings to analyze for confirmation, but the contrast between their songs and those of Say’s trigs (Anaxipha exigua), which were singing nearby up in tall herbaceous vegetation, made the identification clear in my mind before the analysis later confirmed it. According to the comprehensive database used to build the species’ maps for the Singing Insects of North America website, this was the first time the melodious ground cricket was documented in Illinois.

That same day I found them on both sides of that same river in Indiana, adding Lake and Newton County records. With that success in hand, I put some time into searching for melodious ground crickets in other counties and river systems. So far, I have found them along the Kankakee River in Starke and LaPorte Counties, and the Tippecanoe River in Fulton and Marshall Counties, all in Indiana. The significance of this is that the Kankakee River flows west to co-form the Illinois River and flow into the Mississippi. The Tippecanoe joins the Wabash River, flowing south to the Ohio River. Though the Yellow River (a tributary of the Kankakee) and Tippecanoe both cross through Marshall County, their watersheds are well separated by miles of dry moraines and sandy areas. The crickets were absent from bottomland areas that recently had flooded, but rotting logs in slightly more elevated portions consistently held singing crickets.

In Illinois, I found melodious ground crickets in Will County around the confluence of the Kankakee and Des Plaines Rivers, and upstream from there along the Des Plaines in my home county of DuPage. That is as far as I will go with this pursuit as the season winds down, but I expect to add more counties to the list next year. I conclude that at least in this limited but widespread habitat type, the melodious ground cricket can be sought throughout the southern portion of the Chicago region. Here is the map to date:

Map showing counties where I have found melodious ground crickets in the Chicago region, updated with 2017 observations.

I close this post with a couple sound recordings, both made at the Des Plaines Riverway Forest Preserve in DuPage County, Illinois, on September 6. The first, of a melodious ground cricket:

The second recording is the song of a Say’s trig:

Ground crickets, as the name suggests, sing from the ground (or, in the melodious ground cricket, sometimes from within a rotting log). Trigs sing from perches up in the vegetation. In this pair of recordings, the statistics quantify the differences you should be able to hear. The melodious ground cricket had a lower-pitched song, at 5.11 kHz, and a slower pulse rate, at 22/second. The Say’s trig’s corresponding numbers are 6.10 kHz and 31/second. The temperatures near the two singers bring out the contrast even more, the elevated trig at 17.7C and the ground cricket at 19C (i.e., if the trig had been singing at the ground cricket’s temperature, one would expect the dominant frequency and the pulse rate both to be even higher). The two species, as I mentioned above, often occur close to one another, making this difference worth noting.

 

Advertisements

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.

%d bloggers like this: