Early Season Survey: North

by Carl Strang

On Tuesday of last week I drove north to seek early season singing insects in 5 Wisconsin and northern Illinois counties. I was prepared to camp overnight, but with rain in the forecast for the next day I was happy to complete the run in one day.

My first stop was Middlefork Savanna in Lake County, Illinois.

My first stop was Middlefork Savanna in Lake County, Illinois.

Spring field crickets were singing, but vegetation still was wet from an overnight rain, and I was lucky to spot this greenstriped grasshopper to give me that county record.

Spring field crickets were singing, but vegetation still was wet from an overnight rain, and I was lucky to spot this greenstriped grasshopper to give me that county record.

From that point it was rapid-fire site hopping, and I didn’t take many photos.

An exception was this Roesel’s katydid nymph at Wadewitz Nature Camp, a Racine County (Wisconsin) Park.

An exception was this Roesel’s katydid nymph at Wadewitz Nature Camp, a Racine County (Wisconsin) Park.

Wadewitz has extensive grassy meadows, and the biggest surprise of the day was not finding displaying greenstriped grasshoppers in the warm sunny mid-day. Ultimately I was able to find both spring field crickets and greenstripeds in all 5 counties, but several stops were required in some cases.

Mayslake Catch-up

by Carl Strang

Now that we are getting autumnal weather, it’s a good moment to look back at the summer just past, and at the current hints of what is coming. Here are photos from the past month at Mayslake Forest Preserve.

This dorsal view of a black-legged meadow katydid doesn’t show off his colors, but as he pauses between songs we can see the sound-production structures in the bases of his wings.

This dorsal view of a black-legged meadow katydid doesn’t show off his colors, but as he pauses between songs we can see the sound-production structures in the bases of his wings.

Usually I’m good at spotting bee mimics, but this large syrphid fly had me calling it a common eastern bumblebee for several seconds before I realized my error.

Usually I’m good at spotting bee mimics, but this large syrphid fly had me calling it a common eastern bumblebee for several seconds before I realized my error.

According to BugGuide, “larvae are deposit filter-feeders in water-filled tree holes,” which explains why Mallota bautias don’t turn up very often.

When I spotted the scissor-grinder cicada on the horizontal branch I took advantage of the opportunity for an unobstructed telephoto. Only when I was cropping the picture in the computer did I notice the second individual on the vertical branch.

When I spotted the scissor-grinder cicada on the horizontal branch I took advantage of the opportunity for an unobstructed telephoto. Only when I was cropping the picture in the computer did I notice the second individual on the vertical branch.

So much for summer. Now for hints of the season to come.

This brown, probably male, nymph is a greenstriped grasshopper, the species that will kick off the singing insect season next spring. They get started early because they overwinter in this form rather than in eggs as do most of the species singing now.

This brown, probably male, nymph is a greenstriped grasshopper, the species that will kick off the singing insect season next spring. They get started early because they overwinter in this form rather than in eggs as do most of the species singing now.

This Henry’s marsh moth caterpillar was clambering over the tangled stems of a reed canary grass patch, probably seeking a pupation spot for its winter hibernation.

This Henry’s marsh moth caterpillar was clambering over the tangled stems of a reed canary grass patch, probably seeking a pupation spot for its winter hibernation.

These mink scats, freshly deposited on a path near the stream, are the first sign of that species I have seen in a while. Perhaps this mink will center its winter activities around Mayslake’s wetlands.

These mink scats, freshly deposited on a path near the stream, are the first sign of that species I have seen in a while. Perhaps this mink will center its winter activities around Mayslake’s wetlands.

Reptiles and amphibians are moving toward their hibernacula. Recently I spotted a garter snake that looked different from the usual Chicago version of the eastern garter snake.

It was paler around the head and neck.

It was paler around the head and neck.

The side stripe is on scale rows 3 and 4, and other details support the identification of plains garter snake, a new species for the Mayslake list.

The side stripe is on scale rows 3 and 4, and other details support the identification of plains garter snake, a new species for the Mayslake list.

Singing Insect Season Opens

by Carl Strang

The first displays by greenstriped grasshoppers always mark the start of our singing insect season, and this happened yesterday as I heard two displaying males in the prairie at Mayslake Forest Preserve. The rattling crepitations of the display flights at last ended the long winter’s drought. The May 12 date is relatively late, ranking 7th out of the 8 years in which I have kept records. The next anticipated singer is the spring field cricket, which I hope to start hearing in another 2 weeks or so.

The greenstriped grasshopper gets the jump on other singing species because it overwinters as a nymph rather than an egg.

The greenstriped grasshopper gets the jump on other singing species because it overwinters as a nymph rather than an egg.

Sound Ideas: Greenstriped Grasshopper

by Carl Strang

With the arrival of spring it is time to conclude this winter series. Plenty of sound recordings remain to be shared, so I’ll resume Sound Ideas in November or December. The appropriate finale is a recording of the first singing insect we hear each year in the Chicago region, the greenstriped grasshopper. Given the late spring, I am not expecting the first of these before mid-May. I have not found a recording of this species elsewhere:

Male greenstriped grasshopper

Male greenstriped grasshopper

The buzzing sound is the rattling of the male’s wings (crepitation) during short display flights. If you have the volume turned up you may get the impression that this is a loud sound, but it is not. Though it is easy enough to hear, you may well miss it if you are not paying attention to the sounds around you. This common grasshopper occurs wherever there are abundant tall grasses, including open wooded areas, though the greatest densities are in meadows and prairies.

The female gives the species its name, though I have read that occasional brown females or green males have been observed.

The female gives the species its name, though I have read that occasional brown females or green males have been observed.

This is our earliest singer because it overwinters as a nymph, and so can complete its maturation early in the season.

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.

Singing Insect Season Opens

by Carl Strang

Saturday was the spring bird count, and for the first time in recent years I was able to participate. In the early afternoon we were standing on a grassy hill, scanning a pond for water birds in Timber Ridge Forest Preserve, when my ear caught a faint, brief buzzing sound. Then, another. By then my attention had been pulled away from birds, as it seemed I had heard northern green-striped grasshopper displays. I was unable to take the time to confirm it that day, but the next day when I returned I heard many.

Male green-striped grasshopper

Male green-striped grasshopper

Those first observations brought with them the season’s first new question. I was hearing many distinct, if low-volume crepitations, enough to declare the singing insect season open. I did not see any of the grasshoppers, however. Usually their display flights are reasonably conspicuous if you are looking for them. It was moderately windy, though. Were they able to get a normal display out of a shorter, lower flight? Were they somehow rattling their wings without flying? Perhaps later in the season, when displaying grasshoppers are more abundant, I’ll be able to find out.

Incidentally, that May 4 first date is middle-of-the-road. The earliest displays I have observed for that species in DuPage County were on April 3 of last year. The latest starting date was May 16 in 2008. This insect overwinters as a nymph, and so is able to complete its development early in the season.

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.

First and Last Song Dates

by Carl Strang

I now have 7 years’ data in which I have noted the first and last dates on which I heard each singing insect species. This year was characterized by a mild winter followed by a warm spring and then a summer of drought. The mild winter and spring apparently were responsible for this year’s early phenology. First song dates were the earliest I have recorded in DuPage County for 17 of the 21 species for which I have 7 years of records. The chi-squared value of 77.33 (with an expected value of 3 species per cell for each rank of earliest to latest) is, of course, statistically significant.

The greater angle-wing started earlier and finished earlier this year than in any of the previous 6 years.

The greater angle-wing started earlier and finished earlier this year than in any of the previous 6 years.

As for last song dates, singing insects generally finished early this year. Of the 20 species for which I have 7 years’ data, 15 had their earliest or second-earliest ending dates, and the chi-squared value was a statistically significant 22.68. This was not a particularly cold or dry late summer and autumn, so the implication is that singing insects have a fixed rate of attrition or duration of song season, so that an early start results in an early finish. The 12 species for which I have the best, most reliable records do have differences in observed song season lengths (ranges for the 7 years, and ranked lowest to highest: 18-42 days for Roesel’s katydid, 16-52 days for gladiator meadow katydid, 52-96 days for the greater angle-wing, 58-96 days for snowy tree cricket, 67-91 days for the scissor-grinder cicada, 64-94 days for the greenstriped grasshopper, 62-109 days for Linne’s cicada, 72-105 days for the dog day cicada, 81-107 days for the common true katydid, 107-139 days for Allard’s ground cricket, 111-141 days for striped ground cricket, and 113-143 days for Carolina ground cricket).

The number of clear, cold nights seemed high enough in November that they might partly explain the early conclusion of common ground cricket songs this year, especially given the recent study by MacMillan et al. (2012) indicating that there is a metabolic cost to recovering from cold-temperature paralysis. However, I found no significant relationship between last song dates and the number of November days with low temperatures below 33F over 2006-2012 for any of the three species (Spearman’s r values 0.51 for Allard’s ground cricket, -0.39 for striped ground cricket, and 0.33 for Carolina ground cricket). It is interesting, though, that I have seen a few red-legged grasshoppers active a couple weeks after the last ground cricket.

An early December red-legged grasshopper

An early December red-legged grasshopper

This bigger insect may have larger fat reserves to draw upon and so extend its season.

Miscellaneous Encounters

by Carl Strang

It’s time to shake more photos out of the bag, as we are well into the seasonal transition. Back when the weather was hot, a male blue dasher posed at St. James Farm.

For some reason I hadn’t previously been successful in getting a good photo of a male. The forward-cocked wings are a characteristic of the genus.

A few weeks ago some odd looking mushrooms came up beneath a cluster of conifers at Mayslake.

I recognized these from my years in Pennsylvania: old man of the woods. The peculiar flaked surfaces of cap and stem are distinctive.

Recently I shared a photo of a greenstriped grasshopper nymph. At the time, I wondered whether the brown colors of males and the green colors of females might appear as early as the nymph stage. The earlier individual was brown.

Last week I ran across this green one.

So both colors at least are present in the fall. Though I cannot say for sure, the simplest explanation is that the gender-specific colors appear this early in development.

Also last week, a young house centipede explored my office walls.

I marvel at their ability to control all those long legs on a smooth vertical surface.

Of course, one advantage is that the many feet provide lots of little grippers.

Greenstriped Grasshopper Nymph

by Carl Strang

Most singing insects in northeast Illinois and northwest Indiana mature in the latter part of summer, but there are a few species that sing in the spring and early summer. The difference is that most species survive the winter in the relatively safe egg stage, buried in the ground or a plant stem. The exceptions spend the winter as nymphs. Some of these are cicadas, safely protected beneath the soil. Others, however, take a course that seems riskier, having to bury themselves in the vegetation close to the ground or perhaps finding a soil crack that gives them some protection. Because they are small, they are easily missed. Last week I had the good fortune to spot a tiny brown grasshopper.

This was my first look at a greenstriped grasshopper nymph in the autumn.

The head start allows them to mature quickly in the spring, when the tender early plants are less well defended and provide the fodder for rapid growth of herbivores ready to take advantage of them.

Here is a mature male greenstriped grasshopper. The females are green. That does not necessarily mean that the nymph was a male.

The color, the ridge through the eye and the crest on the top of the thorax, as well as the lack of other spring grasshopper species at Mayslake Forest Preserve, leave no doubt of the nymph’s identity. Greenstriped grasshoppers are the first singing insects to display in our area, performing rattling display flights called crepitation. Soon they are followed by other early season species including spring field crickets, protean shieldbacks and gladiator meadow katydids. That gives us singing insect enthusiasts a longer season to enjoy the tiniest wild musicians.

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