The Transformed Block Count

by Carl Strang

The developers who built my subdivision, in their wisdom, decided to plant mostly green ashes along the streets. That brilliance has been answered in the form of an insect, the emerald ash borer. This little invasive ash-killer has done a number on my neighborhood. A series of before-and-after shots follows, going around the block route I follow when I do my standard survey of singing insects in the warm months.

Looking north along my street in 2009.

Looking north along my street in 2009.

The same block now.

The same block now.

Turning west in 2009.

Turning west in 2009.

Same view, 2013.

Same view, 2013.

The next block, looking south in 2009.

The next block, looking south in 2009.

And now.

And now.

The final leg, facing east in 2009.

The final leg, facing east in 2009.

Hard to believe it’s the same block today, but it is.

Hard to believe it’s the same block today, but it is.

Most of the tree loss happened over a brief period of time, the second half of summer last year. Ever the opportunist, I made predictions about the response of the three singing insect species common enough for statistical comparisons between this year and last. Greater angle-wings are tree-dwelling katydids, and so I expected their counts to drop. Carolina ground crickets mainly live beneath foundation shrub plantings, so I expected no significant change. Finally, striped ground crickets prefer sun-lit lawns to shade, so I expected their numbers to increase. I was correct on two of the three predictions.

The Carolina ground cricket median count in 2013 was 7, not significantly different from 2012’s median of 5 (Mann-Whitney U-test of the ranks of all the counts led to a z statistic of 2.05, p>0.01). The median count of striped ground crickets in 2013 was 20, that in 2012 was 11. The comparison of ranks produced a statistically significant z value of 3.89 (p<0.01). I was somewhat surprised at the lack of a demonstrable difference for greater angle-wings (z = 1.00, p>0.01). The 2013 median count was 3, less than the 2012 median of 5, but the difference was not as large as one might expect. There were enough surviving trees of other species to sustain a population of the katydids, and also the removal of the nearer trees made more distant angle-wings more audible.

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.

Fork-tailed Bush Katydid

by Carl Strang

A final gift at Indiana Dunes State Park was of fork-tailed bush katydids singing near the nature center after dark, in the absence of greater angle-wings. Reference recordings of the two species’ songs sound very similar, the single brief buzz of the fork-tailed resembling the alternate song of the greater angle-wing (the latter species also produces an unmistakable ticking sound). Greater angle-wings are very common in northeast Illinois woodlands and residential neighborhoods, but fork-taileds are less so, leaving me wondering if I might confuse them in my surveys. A fork-tailed at the State Park resolved this dilemma.

He was singing in a small tree, just a few feet above the ground.

The fork-tailed’s song is not nearly as loud as the greater angle-wing’s (it is a noticeably smaller insect with narrower, more open wings). The greater angle-wing’s brief song also has a sharp, harshly rasping quality in contrast to the lisping nature of the fork-tailed’s song. Finally, greater angle-wings usually sing from high up in trees. The three fork-taileds I heard at Indiana Dunes all were within 8 feet of the ground. While phonetic renderings can be useful in some cases, I think they can only confuse in this instance: the same or similar syllables (tzip, thisp, etc.) could be used to describe either insect’s song.

Greater angle-wing

Reference recordings commonly are made of captive insects held indoors, with the microphone very close to the singing subject. This makes for a clear, isolated recording, but can produce misleading impressions, as the present case illustrates.

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.

Peak Singing Insect Season Begins

by Carl Strang

By this point in the season we are hearing nearly all the common singing insects in northeast Illinois. First song dates on the whole have been in line with those of recent years, but a few have been relatively late and one was comparatively early.

Snowy tree cricket

My own first observations of singing males typical of residential neighborhoods have included Carolina ground cricket (19 July), common true katydid (also 19 July, a relatively early start for that species), Allard’s ground cricket (22 July), snowy tree cricket (29 July), fall field cricket (30 July, a relatively late start but I had been out of town for a week), two-spotted tree cricket (31 July), Say’s trig (31 July), and greater angle-winged katydid (4 August).

Greater angle-winged katydid

I didn’t get into forests at night until the Roger Raccoon Club campout, so my first date of August 3 for oblong-winged and rattler round-winged katydids has limited meaning. Another forest species that may have started up before my first observation of August 2 was the confused ground cricket.

Black-legged meadow katydid

Our most common large meadow katydid, the black-legged, started up around August 2, a relatively late start for this wetland-edge insect.

Song Peaks

by Carl Strang

My block count data allow me to look at when different kinds of singing insects are most active. I note the time of day for each count, and this year categorized four years’ counts with respect to number of hours before or after sunset.

Two-spotted tree crickets sang the most in the hour after sunset, then continued intermittently through the night.

Sample sizes were 1 count 5-6 hours before sunset, 3 counts 4-5 hours before sunset, 9 counts 3-4 hours before sunset, 13 counts 2-3 hours before sunset, 20 counts 1-2 hours before sunset, 29 counts 0-1 hour before sunset, 61 counts 0-1 hour after sunset, 59 counts 1-2 hours after sunset, 23 counts 2-3 hours after sunset, and 11 counts 3-4 hours after sunset. Some of these sample sizes are small enough to consider the results as tentative (especially for cicadas, which sing before sunset), but on the whole they seem to reflect my more general observations of activity peaks in DuPage County.

Snowy tree crickets peaked 2-3 hours after sunset. Some tree crickets like to nibble on human skin, given the chance.

I found the following peak singing times:  4-5 hours before sunset for Linne’s cicada, 1-2 hours before sunset for the dog day cicada, 0-1 hour after sunset for jumping bush cricket and two-spotted tree cricket, 1-2 hours after sunset for fall field cricket, snowy tree cricket, common true katydid and greater anglewing, 2-3 hours after sunset for striped ground cricket and Carolina ground cricket, and 3-4 hours after sunset for narrow-winged tree cricket.

Narrow-winged tree crickets showed the latest singing peak in my neighborhood, 3-4 hours after sunset.

One particular bias to keep in mind is that some loud singers may drown out others, reducing their counts. For instance, ground crickets are singing at the times when cicadas are active, but I can’t hear them above the cicadas’ loud drones.

Comparative Block Counts

by Carl Strang

In 2010 I made enough counts of singing insects in the small rural town of Culver, Indiana, to compare them to my block counts in Warrenville, Illinois, of the Chicago suburbs.

I walked around similar sized blocks in the two locations, counting the singing insects I heard. This is the south side of the Culver block.

The species count in Culver was 14; differences in species from Warrenville were the absence of Say’s trigs and common true katydids, and the addition of the lyric cicada.

Three species at Culver were abundant enough and showed enough of a difference in median counts to make statistical comparisons worth trying. Culver had more fall field crickets (median count 6, vs. 0 for Warrenville), fewer striped ground crickets (median counts 9.5 and 17 in the period of time covered by the Culver counts), and no statistically significant difference in greater anglewings (median counts 0.5 and 3.5 in Culver and Warrenville, respectively, during the sampling period,).

The Warrenville neighborhood had few fall field crickets in 2010. They were much more abundant in Culver.

I also heard two unfamiliar songs at Culver that may represent additional species. The first of these sang soon after dark on July 31, from a point off the ground and of the speed and pattern of an Allard’s ground cricket, but composed of dry clicks or ticks rather than notes or tones (listening to reference recordings the next day, I thought the most likely possibility was handsome trig).

During a Culver block count on September 4 I heard another unfamiliar song. The temperature was cool, between 55 and 60F, so the song may have been slowed. It had two parts, each consisting of fairly rapid phrases. The first part’s phrases were like doubled ticks, lispy in quality, produced for several seconds. The second part consisted of single ticks, reminiscent of the greater anglewing, lasting much longer (several seconds), and at a distinctly more rapid rate than in the first part. This pattern seems best to fit some member of the subfamily Phaneropterinae, the false katydids.

Block Counts

by Carl Strang

One easy data set to collect in my singing insects study is simply to walk around my neighborhood block (usually when going to my mailbox) and count the insects I hear. For this year I have comparisons between years, a comparison to my new count at my parents’ home in Culver, Indiana, and a consideration of species counts with respect to the time of sunset. Today I’ll focus on this year’s results in my neighborhood.

This photo of my yard is not representative of the neighborhood, in that most of my neighbors are lawn lovers who have very limited shrub and herbaceous plantings.

The overall count in my Warrenville, Illinois, block was 15 species in 2010 (for the complete list go here). No new species were added. Again in 2010 the only species abundant enough for comparisons between years were striped and Carolina ground crickets, and greater anglewing katydids.

Striped ground crickets are named for stripes on the top of the head.

Though striped ground crickets occur in prairies, they really hit their stride in mowed lawns. Not only are they the most abundant singing insect in my neighborhood, their numbers have been very consistent over the years with median counts of 13, 12, 12 and 14.5 in the respective years of 2007 to 2010. None of these differences are statistically significant.

The ticking song of the greater anglewing is a distinctive summer evening sound wherever this katydid occurs.

Carolina ground crickets, which hang out in denser plantings, and tree-dwelling greater anglewings likewise showed no changes between 2009 and 2010 (this year’s median counts 4 and 1, respectively).

Wings Flash

by Carl Strang

I was finishing a bike workout, pedaling the final blocks toward home, when a large insect flew across my path. Green, and with wings and legs widely spread, it gave me the split-second first impression was that I was seeing a praying mantis. But the wings were wrong, proportions were wrong, and it didn’t have the Edward Gorey weirdness of a mantis’ profile in flight. The insect turned around, flew back across the street, and crash landed on a lawn. I stopped, dug out the phone, and used it to photograph what I now realized was a greater anglewing.

The spread of that katydid’s wings in flight reminded me of another recent observation. I have taken opportunities to watch a few Texas bush katydids singing, and have been struck by how much the wings flip out to the sides, especially when compared to the more subtle vibrations of singing meadow katydids. I suspect I may be onto what made the Texas bush katydid I observed at Pratts Wayne Woods have such a slurred short-song, with a quality reminiscent of the broad-winged bush katydid’s corresponding advertisement. Here’s another shot of the Pratts Wayne katydid.

It’s missing a wing tip, and there also was scarring near the base of the left forewing. Such damage may well have caused the dramatically flipping wings to sound abnormal when rubbing together to produce the song. The typical crispness that would come from, say, this undamaged conspecific I saw in the dolomite prairie at Waterfall Glen, is compromised.

By the same token, the broad-winged bush katydid’s wings are shorter and wider, and might be expected to flop around more, so that the slurring typical of that species’ short song results. Experimental manipulations suggest themselves, but I’m not interested in captive studies at present.

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