Field Crickets 2015

by Carl Strang

The spring field cricket and the fall field cricket are our most common members of their genus, both found in all the counties of the Chicago region. They are sibling species, identical in appearance and in song, differing only by season.

Fall field cricket

Fall field cricket

The only way to be sure that spring field crickets are done for the year, or that fall field crickets have begun, is to check the rare locations where only one of the two occurs. I have adopted the practice of counting them on my weekly bicycle rides through nearby Fermilab, where both species live in good numbers. Last year’s pattern was clear.

Two clear peaks in numbers with a well-defined valley between: spring field crickets peaked in mid-June 2014, fall field crickets in mid-September, with a separation in late July.

Two clear peaks in numbers with a well-defined valley between: spring field crickets peaked in mid-June 2014, fall field crickets in mid-September, with a separation in late July.

This year things were different in some ways, but the general pattern held.

The fall field cricket pattern in 2015 again was well defined, with an earlier peak at the beginning of September. The dividing point again was in the second half of July.

The fall field cricket pattern in 2015 again was well defined, with an earlier peak at the beginning of September. The dividing point again was in the second half of July.

The spring field cricket counts were more chaotic, and lower than those for 2014. Weather was a factor here, often rainy, often windy. This affected my ability to count them, but I think there were indeed fewer than in 2014, and also more fall field crickets than last year.

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.

 

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.

 

Return to Midewin

by Carl Strang

Recently I spent an enjoyable afternoon at the Midewin National Tallgrass Prairie, in Will County, Illinois. My main target was a swale in the northwestern portion of the property.

In one place the swale expands into a ponded area that in this wet year was around 50m wide and a few hundred long.

In one place the swale expands into a ponded area that in this wet year was around 50m wide and a few hundred long.

I added 3 county species records in and around the swale, but all are common in the region and so not the exciting rarities I’d hoped for.

This Forbes’s tree cricket was one of the three. It was perhaps the darkest individual I have seen in Illinois, and more typical of the Indiana coloration in my experience.

This Forbes’s tree cricket was one of the three. It was perhaps the darkest individual I have seen in Illinois, and more typical of the Indiana coloration in my experience.

As I returned to my car, wading through a nicely developing restored prairie, I spotted an unfamiliar grasshopper.

It held still while I took side and dorsal photographs. The color pattern and sculpturing pointed to the band-winged grasshopper subfamily.

It held still while I took side and dorsal photographs. The color pattern and sculpturing pointed to the band-winged grasshopper subfamily.

Note the white X marking on the pronotum (dorsal thorax). That rang a bell, and ultimately helped with the identification.

Note the white X marking on the pronotum (dorsal thorax). That rang a bell, and ultimately helped with the identification.

Unfortunately the hopper evaded me when I tried to catch it so as to check out the hind wing color. As I continued to walk out I saw a couple displaying grasshoppers with bright yellow hind wings, which I was unable to see up close. I made the assumption that they were the same as the photographed hopper, but this proved not to be the case. It turned out to have been a dusky grasshopper, Encoptolophus sordidus, which has an essentially colorless hind wing. It was the first of that species I have found, which always is exciting, but now I know there’s also a yellow-winged species I will have to go back and hunt down on a future visit.

While I was photographing the dusky grasshopper, a nearby movement caught my eye, and led me to a new experience. It was a ballooning spider, half an inch long. I had heard of this but never seen it, and did not expect that such a large individual could travel in that way. The spider sends out a strand of silk which grabs the wind and carries the spider through the air.

The spider had landed on a stalk, and paused long enough for me to get some photos. I haven’t had time yet to try for an ID.

The spider had landed on a stalk, and paused long enough for me to get some photos. I haven’t had time yet to try for an ID.

The spider didn’t wait long before it turned to face into the wind.

The spider didn’t wait long before it turned to face into the wind.

It began shooting out new strands of silk, obviously not satisfied that it had traveled far enough.

It began shooting out new strands of silk, obviously not satisfied that it had traveled far enough.

As I continued my walk to the car I noticed several strands of silk streaming from plant tops, and felt that I had learned something new about them.

I’ll close with a couple photos from other parts of Midewin.

This female short-winged green grasshopper was a county record.

This female short-winged green grasshopper was a county record.

A female fall field cricket posed nicely on a trail.

A female fall field cricket posed nicely on a trail.

Sound Ideas: An Odd Trio

by Carl Strang

Today’s chapter in the Sound Ideas winter series is a recording from the evening of September 4 last year. I made it in the Miller Woods portion of the Indiana Dunes National Lakeshore. Three very different singing insects can be heard distinctly throughout:

The principal target of this recording produced the annoying, continuous buzzing sound. If you had been there, you would have remarked at how loud this insect was. It was a robust conehead.

Male robust conehead, singing posture

Male robust conehead, singing posture

This katydid has a sibling species, creatively named the false robust conehead (Neoconocephalus bivocatus). I haven’t documented bivocatus in the Chicago region, but there are a couple old possible records, so occasionally I record an individual and check the pulse rate and pattern. So far, all have been good old Neoconocephalus robustus.

The other two members of that night’s trio both produced regular, brief chirps: one higher pitched and very regular in its rhythm, the other much lower and a little less regular. The higher pitched singer is famous for the way its chirping rate varies with temperature: count the chirps in 13 seconds, and add 40 to get the degrees Fahrenheit. We know this singer as the snowy tree cricket.

Snowy tree cricket male, taking a break from singing to snack on skin.

Snowy tree cricket male, taking a break from singing to snack on skin.

That leaves the bass section. The lower pitched continuo is the product of a northern mole cricket. This swale area of Miller Woods is one of only 3 locations where I have found this species to date. I don’t have a photo to show you. True to his name, the mole cricket sings from within his tunnel, and I haven’t yet had a photo op with the critter.

Ah, yes. I see an insistent hand upraised in the back of the class. Yes? Ah, very good. Yes, there is a fourth, more intermittent performer here. Those few added chirps are a fall field cricket’s, practically ubiquitous at this point in the season, and determined to insert himself into any ensemble.

Burn Aftermath

by Carl Strang

Mayslake Forest Preserve had much of its acreage burned for management purposes last spring, as described earlier. One result, aided by good amounts of seasonal rains, was a very lush, tall growth of prairie vegetation.

Part of one of Mayslake’s prairies on August 12.

Part of one of Mayslake’s prairies on August 12.

What impact did this have on the prairie insects, in particular the singing insects? I expected the species that lay their eggs in the tops of prairie plants would be impacted the most, but those that lay their eggs in the soil would be relatively unharmed. It was clear, though, that despite the unusual completeness of the burn, small patches of prairie here and there were missed by the fire, as were wetland and woodland edges, and there were portions of the preserve not included in the burn plan. These provided a reservoir from which affected species might spread.

My impression through the season was that the numbers of fall field crickets (a species which lays its eggs in the soil) were down from last year, but the numbers don’t bear this out. Counts on the whole in the various habitats are similar between this year and last. Likewise, the 3 species of common ground crickets are so abundant in all habitats that no quantitative comparison seems necessary.

Greenstriped grasshoppers overwinter as nymphs, and so are more vulnerable. If anything, however, their numbers seemed somewhat larger in all habitats, including burned ones.

Greenstriped grasshopper nymph

Greenstriped grasshopper nymph

Unfortunately, confusion about the species identity of meadow-dwelling tree crickets (described in a post earlier this week) prevented my gathering quantitative data last year. I did record numbers this year, though, and attended their locations through the season. It was clear that the earliest singers in this group were concentrated in unburned areas and around the edges of burned areas, where they might have hatched from eggs in the unburned adjacent habitats. As the season progressed, though, these tree crickets (mainly Forbes’s tree crickets) proved to be very mobile, and spilled into the hearts of the burned areas (where the forage no doubt was richer thanks to the burn, and where there was an advantage to escape the competition). Though numbers overall may have been down a little, there were plenty of these tree crickets to ensure a rapid population recovery.

As for meadow katydids, they all to some extent concentrate in wetlands, which were scorched in places but not thoroughly burned. There again appeared to be plenty of survivors to reproduce and fill the habitat.

Perhaps the most interesting observation relevant to this question this year was a big drop in wasps of the genus Sphex. There were a lot of these last year, crowding into the areas where swamp milkweeds were blooming. The great black wasp and great golden digger specialize in capturing katydids to feed their young, and potentially can influence populations significantly. I saw only a very few of those wasps this year. As they overwinter underground, I doubt the fire had anything to do with their absence. Whatever the cause, their departure further assured a successful reproductive season for the katydids of Mayslake.

Great golden digger

Great golden digger

The upshot of all of this is that the extensive spring burns, while they may have had some minor and spotty effects on singing insect populations (and, by extension, other invertebrates), did not devastate any populations as far as I can tell. This was somewhat surprising, but in retrospect it becomes clear that it would take an extraordinarily complete and extensive burn to have a long-term impact. Refugia within and without the burn area seem likely to carry populations through enough to recover from this disturbance.

Field Cricket Survey Update

by Carl Strang

The familiar chirps of field crickets can be heard through the warm months, thanks to two different species with identical songs: the spring field cricket, which begins in May and continues into July, and the fall field cricket, which begins in mid-July and continues until severe frost ends its season. I have noticed that the two species do not always occur together, and in recent years have been surveying DuPage County to map the pattern.

Fall field cricket (female). The spring field cricket looks just like this; only their seasons separate them.

Fall field cricket (female). The spring field cricket looks just like this; only their seasons separate them.

Here is the recently updated map. Green circles represent places where both species occur, blue ones mark spring field cricket-only locations, and yellow indicate where I have heard fall field crickets but not the spring species.

Here is the recently updated map. Green circles represent places where both species occur, blue ones mark spring field cricket-only locations, and yellow indicate where I have heard fall field crickets but not the spring species.

Both kinds of crickets are well distributed in the county, and with only a few exceptions, fall field crickets are ubiquitous. Some of the blue circles represent fairly large areas, though, and at some point I will want to study them more closely. Before I do that, however, I will want to spot check at least some of the places where I heard only fall field crickets. My surveys have taken place in the evenings, but recently I read a study which indicated that while fall field crickets have their peak singing time in the evening, spring field crickets are more active in the morning. It may be necessary to repeat the entire spring field cricket survey. Until then, my hypothesis is that the rigors of overwintering as nymphs place a greater limit on where spring field crickets can live. Fall field crickets, more secure in their buried egg form during the cold season, have more habitat latitude.

Spring Field Cricket Survey

by Carl Strang

The spring and fall field crickets arguably are our most familiar singing insects. The two species are common, span the season from spring to late fall, and their identical songs are easily recognized chirps. Physically, spring and fall field crickets are essentially identical.

Fall field cricket (female)

Fall field cricket (female)

Developmentally and ecologically they are different, however. These days we are hearing spring field crickets, which overwinter as nymphs, mature in late April or May, and finish in mid-July. The figurative baton then passes to the fall field crickets, which overwinter as eggs in the soil, mature after mid-July, and continue into October or early November. These are two different survival regimes, and the spring field crickets arguably have the tougher challenge. Winter would seem to be easier to survive as a buried quiescent egg than as a nymph. I have been testing this idea by surveying the two species in DuPage County, and recently completed the spring field cricket part of the survey. I drove 3 routes in eastern DuPage in the evenings, listening with the car windows open. The crickets’ songs are sufficiently penetrating that I can expect to hear them, at least well enough to get a general sense of where they are and where they’re not.

Here’s the composite map to date. Green dots represent locations with both species, yellow show places with only fall field crickets, and blue with only spring field crickets (so far).

Here’s the composite map to date. Green dots represent locations with both species, yellow show places with only fall field crickets, and blue with only spring field crickets (so far).

As you can see, there are many blue dots in the eastern half of the county. Many, perhaps most or all, will become green when I repeat these routes in late summer or early autumn. The impression I formed while driving around is that there are pockets of crickets, scattered and somewhat isolated, with a lot of empty space between them. Some populations are relatively large, but some of the blue dots represent single singers. Spring field cricket habitat is narrower, it seems, needing to supply better winter shelter, but I will be better able to draw tentative conclusions after the survey drives for fall field crickets later this year.

The Burn Extended

by Carl Strang

As I reported earlier, Mayslake Forest Preserve had a thorough controlled burn of its highest quality restored prairies in late March. On Monday I discovered that had not been the end of it. The Forest Preserve District’s crew returned and conducted a burn of the north savanna and adjacent meadow areas.

The top of the savanna ridge after the burn.

The top of the savanna ridge after the burn.

This burn likewise was a good one, leaving little in the way of last year’s dead herbaceous growth. This is the most complete burn coverage of the preserve in the 5 years I have been there, and along with the vegetation went the eggs and nymphs of many species including tree crickets, meadow katydids, and greenstriped grasshoppers. From a scientific standpoint this is more opportunity than it is disaster, as there are no rare species at Mayslake. The remaining, unburned meadows and wetlands, as well as a few pockets that did not burn well, will be source areas for the spread and repopulation of the burned areas by survivors. Also, the fire probably did not affect the species whose eggs were in the soil or treetops, including fall field crickets, ground crickets, and some katydids.

The burn extended into adjacent meadows to the east and north.

The burn extended into adjacent meadows to the east and north.

I will be able to make a number of comparisons to assess the impact of the fire. How well will the affected insect species spread from the refugia, and where will they go first? Will there be differences between burned and unburned areas in the unaffected species, which stand to benefit from the higher quality plant growth in the wake of the burn? What will be the species count differences between years in the various habitat blocks? What about the impact of specialist predators and parasites? The first species to note will be the greenstriped grasshopper, which has been common in the early season.

Field Cricket Final

by Carl Strang

In September and early October I revisited driving routes I had followed in the spring, listening for fall field crickets (FFC) as I had done in May and June for spring field crickets (SFC). Then, I had noticed that SFC were limited largely to places where dense herbaceous vegetation provided shelter for overwintering nymphs. FFC spend the winter as eggs buried in the soil, and so are less vulnerable to the stresses of the cold season. Here is the current map showing the distribution of the two species in DuPage County:

Green circles represent locations with both spring field crickets and fall field crickets. Blue circles indicate spring field crickets only, yellow indicate fall field crickets only.

Clearly both species occur together in most places. Fall field crickets are more likely to occur alone than spring field crickets, in keeping with the spring observation. This year’s surveying was done in western DuPage, and next year I plan to fill in more of the eastern part of the county. If the results continue to show the pattern that appears to be emerging to date, the eastern part of the county, which became urbanized earlier and more completely than the western part, will continue to show fewer SFC because of its historical paucity of safe nymphal overwintering sites. The existence of locations with SFC but no FFC remains to be explained.

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