Singing Insects in Transition

by Carl Strang

We are at a point in the season where the spring-singing insects are finishing, and the early summer brings new voices to the chorus. Green-striped grasshoppers seemed to tail off rapidly in their crepitating flights this year. I have heard very few in recent weeks.

The male green-striped grasshopper usually is brown. He’s the one who does the displaying.

The male green-striped grasshopper usually is brown. He’s the one who does the displaying.

The object of his displays usually is green, and a bit bigger than him.

The object of his displays usually is green, and a bit bigger than him.

Roesel’s katydids rapidly are increasing the number of buzzes they are contributing to the meadows and prairies.

Note the blur in the wings as this short-winged Roesel’s katydid sings. Some individuals have much longer wings.

Note the blur in the wings as this short-winged Roesel’s katydid sings. Some individuals have much longer wings.

Over the weekend I heard first songs from three additional species: Linne’s and dog day cicadas, and the gladiator meadow katydid.

This was one of several gladiators singing beside the Regional Trail in south Blackwell Forest Preserve Saturday evening.

This was one of several gladiators singing beside the Regional Trail in south Blackwell Forest Preserve Saturday evening.

Those Tibicen cicadas, especially, characterize the sound of summer for me.

Kendall County Singing Insects

by Carl Strang

On Friday I took a vacation day to begin surveying singing insects in Kendall County, Illinois, just southeast of my home county of DuPage. It was a good, productive day, yielding a total species count of 19.  There are some high quality wet to mesic forests and restored prairies in the four sites I visited.

The best quality forest was in Richard Young Forest Preserve. There were few invasive plants in this sugar maple forest, which was cut by a nice stream or two and had a beautiful little kame named “Hepatica Hill.”

The best quality forest was in Richard Young Forest Preserve. There were few invasive plants in this sugar maple forest, which was cut by a nice stream or two and had a beautiful little kame named “Hepatica Hill.”

Harris and Hoover Forest Preserves show promise for future visits, though I did not pick up many species there on this trip. The most extensive area was Silver Springs Fish and Wildlife Area (formerly Silver Springs State Park).

Silver Springs has good bottomland forest along the Fox River, and a wide range of open lands. This meadow had many prairie grasses mixed in.

Silver Springs has good bottomland forest along the Fox River, and a wide range of open lands. This meadow had many prairie grasses mixed in.

This restored prairie was one of my favorite locations, yielding several singing insect species.

This restored prairie was one of my favorite locations, yielding several singing insect species.

I did not find much in the way of marshland, and no dry oak woodlands or savannas. I will need to see if Kendall County has good examples of such habitats. As for singing insects, highlights included good numbers of broad-winged bush katydids and a couple dog day cicadas, two of the species I am following for southern range boundaries. The dominant singer was the lyric cicada, with loud choruses providing a continuous background through the day.

This gladiator meadow katydid gave me a photo opportunity. Though the reflections from the flash reduce the quality of this as an image, they do a nice job of highlighting the relatively straight rear boundary of the pronotum, helpful in distinguishing this species from the common meadow katydid.

This gladiator meadow katydid gave me a photo opportunity. Though the reflections from the flash reduce the quality of this as an image, they do a nice job of highlighting the relatively straight rear boundary of the pronotum, helpful in distinguishing this species from the common meadow katydid.

The one species that I heard for the first time this year was the Nebraska conehead.

Many Nebraska coneheads were singing along River Road in the north part of Silver Springs and in residential properties adjacent to it. This one agreeably posed.

Many Nebraska coneheads were singing along River Road in the north part of Silver Springs and in residential properties adjacent to it. This one agreeably posed.

I hope to get back to Kendall County at least one more time this year.

The Other Side of Range Extensions

by Carl Strang

The aspect of singing insect studies that has been of greatest general interest, and about which I have presented talks most frequently, is range extensions. Most of the several examples uncovered so far have been northward extensions of species ranges, and it is easy to jump to the conclusion that this is a product of global climate change.

The first species I found well north of where it previously had been known was the broad-winged tree cricket.

The first species I found well north of where it previously had been known was the broad-winged tree cricket.

If climate is the primary influence in these range extensions, we would expect the southern boundary of a species’ range to shift north as well. However, sticking with the example of the broad-winged tree cricket, its range has expanded south as well as north. I know that only because Tom Walker, the authority responsible for the Singing Insects of North America website, informed me that he has found them spreading down into parts of Florida where they had not been before.

Documenting an expansion northward is easier than demonstrating a disappearance in the south portion of a species’ range. It is easier to prove a positive than a negative. Also, when one has limited time and financial resources, it is not possible to travel south and conduct the necessary regional surveys. So, what to do?

The best idea I have had so far is to identify species whose southern range boundaries occur in my region, and make a point of documenting their presence and estimating their abundance from year to year. There are four best candidates.

The dog day cicada Tibicen canicularis has the northernmost southern range boundary. It is mapped down into the very northern edges of Indiana and Illinois, but I have found it a little farther south, at Braidwood Dunes in Will County, Illinois, and in southern Marshall County, Indiana. My notes suggest that its numbers may vary considerably from year to year in the latter location.

Dog day cicada

Dog day cicada

The broad-winged bush katydid Scudderia pistillata is mapped a little farther south, but I have found it infrequent in DuPage County, Illinois, and its season of activity seems to conclude sooner here than it does farther north. So far my surveys have turned it up in Lake County, Illinois, as well, but not farther south.

Broad-winged bush katydid

Broad-winged bush katydid

The striped ground cricket and sword-bearing conehead are abundant in the region. Their southern range boundaries are mapped about half a state south, but that is the same distance as a number of the northern range shifts I have observed. If entire ranges are shifting, one would expect them to be more scarce.

Sword-bearing conehead

Sword-bearing conehead

This is yet another topic of interest I am keeping in mind while surveying the region’s singing insect species.

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.

Learning to Identify Insect Songs

by Carl Strang

One of the obstacles to a singing insect monitoring program is the large number of various songs that need to be learned for identification. This is not really much different from learning bird songs for breeding bird monitoring, however (except that the total number of species is smaller here). Instead of being daunted by the entire process, it is possible to take the learning process in stages, beginning with the songs that are common and easy to recognize, the ones you have been hearing all along but simply didn’t have the species labels. Here is a list of a dozen suggested species to start with in the first stage: spring field cricket/fall field cricket (their songs are identical), Allard’s and striped ground crickets, snowy tree cricket, common true katydid, black-legged meadow katydid, greater angle-wing, round-tipped conehead, dog day cicada, scissor-grinder cicada, and Linne’s cicada (for more information on these species, try the tags at the head of this post).

Snowy tree cricket, one of the species on the starter list

This list and those that will follow are for northeastern Illinois and northwestern Indiana. There would be substitutions in other parts of the country (I encourage readers elsewhere to make comments here with their own suggestions). Go to reference recordings of these species’ songs, either on-line at the Singing Insects of North America website or through the CD that accompanies the Songs of Insects book. It is not too late this year to hear many of the species on this list on the warmer days, though some are finished or nearly so.

My recommended species list to focus on in the second stage of learning consists of 8 species and groups of species: greenstriped grasshopper, gladiator meadow katydid, Roesel’s katydid ( three species that sing relatively early in the season), and then later, Carolina ground cricket, Say’s trig, sword-bearing conehead, two-spotted/narrow-winged tree crickets (no need to worry yet about separating the two), and the meadow tree cricket group (3-4 species whose songs are essentially identical to the ear and will remain so).

Roesel’s katydid is a species from the second-stage list.

This list of common species either will take you to additional, though still readily available, habitats, or else require a little more of a practiced ear (which practice you got with the first species group). In particular, seek out and spend some time getting familiar with the songs of the Carolina ground cricket and Say’s trig. They need a little more effort to recognize in the field, but once you have them, they will be touchstones for many other species (much as robin songs are for learning bird vocalizations). If you are starting now, you might push the Carolina ground cricket to the first list, as it is one of the few species singing on the cooler days and evenings.

Once you have mastered the second list of species, you are ready for the more subtle distinctions needed to distinguish the songs in the third species list. This includes separating out the song of Linne’s cicada from similar songs by the lyric cicada, and in some areas, swamp and/or northern dusk-singing cicada.

Linne’s cicada

Also, by this point you are ready to distinguish the two-spotted tree cricket song from that of the narrow-winged tree cricket. Also, the broad-winged tree cricket should stand out now from other long-trilling species. In addition, you no doubt have noticed and begun to puzzle out other species that are more idiosyncratic in their distribution or smaller in numbers that you have encountered in your favorite places.

And that brings you to the fourth stage, learning the songs of whatever remaining species may live in the area you wish to monitor. For this you will need a regional guide. In the Chicago region, you can meet this need with the guide I am developing. It is available for free as a .pdf e-mail attachment. Simply request it at my work e-mail address: cstrang@dupageforest.com

As you are learning and listening, pay attention to which songs you can hear clearly, and at what distances, and which are marginal. This will inform the limitations you will need to address or acknowledge in your monitoring.

Early Singing Insects

by Carl Strang

To this point in the season I have heard singing males of 10 insect species in northeast Illinois. All but one began earlier than in any of the years from 2006 to 2011. This is consistent with more general insect phenology this year, and is attributable to a mild winter and a warm March which heated the soil earlier than usual. The only species with a later starting date was the spring field cricket, a species I usually hear first while running or bike riding, activities my back trouble prevented during the critical time period. And yet, despite that limited mobility, I have recorded dates for the other 9 species that ranged 5-22 days earlier than in any previous year (4 of the previous records were in 2007, 5 in 2010, 1 last year; they add up to 10 because of a tie). The only other case perhaps worth singling out was the broad-winged bush katydid, 22 days earlier than last year’s previous record. This species is not abundant or widely distributed, and I suspect it has a longer, earlier season than I have realized before. I should make some effort in future years to get a better handle on its starting and ending dates.

Broad-winged bush katydid

For those who may be interested, here are all the first song dates this year so far. Greenstriped grasshopper 3 April, 17 days earlier than the previous record. Spring field cricket 25 May, 20 days later. Roesel’s katydid 29 May, 11 days earlier. Protean shieldback 5 June, 7 days earlier. Linne’s cicada 14 June, 12 days earlier. Gladiator meadow katydid 14 June, 7 days earlier. Dog day cicada 15 June, 5 days earlier. Scissor-grinder cicada 19 June, 13 days earlier. Broad-winged bush katydid 23 June, 22 days earlier. Lyric cicada 24 June, 6 days earlier.

First Song Dates, 2011

by Carl Strang

As I wrap up the year’s singing insects field study I am interested in making summary comparisons to earlier years. Last week I reported on block counts. Today’s focus is on first song dates.

The dog-day cicada’s first song date of July 4 was the fourth-earliest for that species among my 6 years of observations.

I have 6 years of first song date records for 23 species. None of the 2011 dates were earliest for a species, 1 was second-earliest, 5 were third-earliest, 10 were fourth-earliest, 3 were fifth-earliest, and 4 were latest. This was different from the expected even distribution of 3.8 in each category, and it produced a χ2 test statistic of 16.54, indicating a statistically significant departure from the expected (P<0.01). The biggest contribution to the χ2 value was from the middle-of-the-road fourth-earliest category, suggesting this was an unremarkable year for starts, neither early nor late.

The snowy tree cricket was another species whose first song date was fourth-earliest. The July 29 date was 16 days later than in 2010.

Focusing on the readily observed species, for which I have some confidence that my observations have strong validity, first song dates were a median of 9.5 days later in 2011 than in 2010 (n = 26 species, range 17 days earlier to 26 days later), and 2.5 days earlier in 2011 than in 2009 (n = 24 species, range 24 days earlier to 22 days later). Those values are comparable to the late flowering phenology pattern I observed at Mayslake Forest Preserve this year, which in turn reflected the soil-chilling February blizzard and the cool spring.

Block Count Summary

by Carl Strang

Neighborhood block counts are a survey method I have developed in my singing insects study. They consist of walks around the block in my residential neighborhood in Warrenville. I record the time and temperature, and count only the insects whose individual songs I can distinguish from the general background of tree cricket and ground cricket songs. I try to include a mix of times, especially early in the season to include cicadas, but concentrate most of the effort after dark when most species are singing. The overall species count in 2011 was 14 (no new species this year).

One of the streets on the block.

Most of these insects do not occur in high enough numbers to permit statistical comparisons between years. The high counts for each species this year were as follows: 1 for fall field cricket, jumping bush cricket, Say’s trig, and Davis’s tree cricket; 2 for Allard’s ground cricket and dog day cicada; 3 for snowy tree cricket, 4 for narrow-winged tree cricket, 5 for common true katydid, 8 for two-spotted tree cricket, 10 for Linne’s cicada, 14 for Carolina ground cricket, 16 for greater anglewing, and 26 for striped ground cricket. Most of these are typical of the past five years. Apart from statistical comparisons to follow, there seems to have been a decline in fall field crickets over that period (high counts of 5 in 2007, 4 in 2006, and 1 in the recent years, but in 2011 that count was on only one occasion).

Only three species occur consistently in large enough numbers to justify statistical comparisons between years. There never have been statistically significant differences between adjacent years in striped ground cricket counts, and the same was true in this year’s comparison with 2010 (overall medians 14.5 in both years; Mann-Whitney U-test, z = -0.14, P>0.01). Carolina ground crickets likewise were not different (median 4 in 2010, 7 in 2011; z = -2.07, P>0.01). Greater anglewing counts did show a statistically significant increase over last year (median 1 in 2010, 4 in 2011; z = -3.30, P < 0.01), and in general they and the fall field crickets have been the most volatile.

Assorted Photos 1

by Carl Strang

Photo opportunities arise frequently during my preserve monitoring walks at Mayslake Forest Preserve. Sometimes these lead to blog posts, sometimes they simply are for identifying organisms when I’ve forgotten the distinguishing features, and sometimes they improve or add to my collection of species portraits. This week I’ll share a few of the last.

Hummingbird at cardinal flower.

That first one won’t win any photography prizes, but it does serve to document the use of one plant species for food by the bird, and the use of the bird by the plant for pollination. Another bird photo op came when I encountered a couple cooperative house wrens.

This bird adopted a humorous pose while grooming itself.

I also added to my photos of singing insects. The only picture I had of a Carolina grasshopper was one I took in Canada, and wanted a local example.

An area recently cleared of brush at the edge of the north stream corridor prairie has hosted a concentration of Carolina grasshoppers this year.

Live Tibicen cicadas usually are too high up in trees to photograph. When I found a dog day cicada singing from a tall coreopsis stem in the middle of the prairie I got a rare opportunity.

The wind was swaying the plant, so the insect isn’t perfectly sharp, but close enough for practical purposes.

More photos tomorrow.

Singing Insect Season Heats Up

by Carl Strang

We have entered the part of the season when first appearances of mature singing insects accelerate. The transition in DuPage County began with the first gladiator meadow katydid singing on June 30. This was relatively early, though 9 days later than the earliest I have heard them in the 6 years of my study.

Gladiator meadow katydid.

I have to append my description of this species’ song. In the past I have said that they seldom include ticks in their song. I have been listening closely this spring, and in fact there usually are very faint ticks between the much louder buzzes. The ticks are variable. Commonly they seem to trail off from the end of a buzz rather than to lead into the next one as is typical of meadow katydids, but sometimes the latter pattern appears. Most of them have an irregular stuttering pattern in the ticks, though occasionally they are regular. The main distinction remains, however, that the ticks are very faint compared to the volume of the buzzes.

The “annual” cicadas of genus Tibicen were led in by a Linne’s cicada on July 3. The next day brought the first canicularis (dog day) cicada song, in my own yard. A lyric cicada debuted on the 11th, and finally a scissor-grinder (pruinosa) offered the first song on July 15. All of these were middle-of-the-road start dates.

Ground crickets also are due this time of year. The first was, as usual, a striped ground cricket, on July 13.

The most recent start-up was by broad-winged bush katydids, several of which were singing their short, lisping day songs at Fermilab on July 15, an early start for the species.

It’s appropriate here to remind you that I can e-mail my free guide to singing insects of the Chicago area to those who request it at my work address: cstrang@dupageforest.com

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