Bush Cicadas

by Carl Strang

Illinois has lost nearly all the remnants of its original prairie. Thanks to the efforts of conservation agencies and private organizations you can find prairies to enjoy, but these are restoration projects for the most part. Restored prairies are nice gardens, but they lack a significant portion of the animal life. It’s a mistake to assume that “if you build it they will come.” Too many obligate prairie insects and other animals are not good dispersers. The highest priority has to be preserving the remnants, when there is a choice between devoting resources to that or to developing restorations.

A case in point is the prairie cicada, which I have featured here in the past. Another is the bush cicada. I made a trip south of the Chicago region last week to get some experience with that species, so I would know what to listen and look for in my 22-county survey area. A 2-hour drive took me to the southern fringe of Iroquois County, to the Loda Prairie State Nature Preserve.

This remnant is only 12 acres, but its quality is excellent.

This remnant is only 12 acres, but its quality is excellent.

The term “charismatic fauna” is over-used. The bush cicada is the first Illinois insect I have encountered to which I would apply that term.

For one thing, they are big and colorful.

For one thing, they are big and colorful.

They also are noisy like the other species in genus Neotibicen (formerly Tibicen, the change justified in a paper just out this year from the UConn cicada group plus an Australian researcher). I was pleased to find bush cicadas are fully as audible as our familiar Neotibicen species.

Linne’s cicada, for instance.

Linne’s cicada, for instance.

The song is like a slowed lyric cicada song, the pulse rate closer to that of Linne’s but with sharp, separate pulses. The singing was in bouts, with sometimes 10 minutes of silence between, so that the males seemed to cue their singing off of one another. They also were very active, many of the males flying to a new perch after every song. Though their flight generally was well controlled, once one bounced off the side of my head.

A male bush cicada in full song.

A male bush cicada in full song.

In the following days I sought them in several Chicago region counties, without success. The silence of those prairie remnants, some suffering from invasion by gray dogwood and other problem plants, was a sad contrast to Loda Prairie. In fairness, though, the bush cicada is primarily a southern and western species that may never have reached into the Chicago region. That won’t keep me from continuing to seek it here, though.

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.

Seeking the Lyric Cicada

by Carl Strang

Last Thursday I searched for the northernmost lyric cicadas, having found them superabundant in Kendall County and absent in the portions of McHenry County I surveyed. This is a woodland species that seems especially common in bottomland forests, so I took advantage of our glacial legacy and followed rivers north and south (rivers developed in low zones between the concentric end moraines), but also stopped at other woodlands along the way.

Lyric cicada, Tibicen lyricen

Lyric cicada, Tibicen lyricen

There clearly is a gradient in density from south to north. In Kendall County, and along the Des Plaines River at the south edge of DuPage County, large numbers of lyric cicadas form loud choruses. In central DuPage County, at locations such as Fullersburg Woods and Mayslake, this is a regular part of the insect fauna, but they are down to countable numbers of individuals.

The clearest indication came as I followed the West Branch of the DuPage River, and continued north beyond it.  At Blackwell Forest Preserve, in west central DuPage County, there was a ratio of 11 lyric cicadas to 18 or so Linne’s cicadas (= 0.61; Linne’s has a fairly uniform density through the area). At Elsen’s Hill, a few miles farther north, the ratio was 4:7 (0.57).  Several miles farther north, at West Branch Forest Preserve, the ratio was 3:7 (0.43). The farthest north I found this species was at Shoe Factory Woods, in north Cook County, where the ratio was 2:12 (0.17).

Shoe Factory Woods has some good prairie and savanna restorations going.

Shoe Factory Woods has some good prairie and savanna restorations going.

By that point, though, cicadas had entered their afternoon lull, and I wasn’t hearing many of any species. Shifting west and driving south along the Fox River, I heard the next lyric cicada at the north edge of St. Charles, a point close in latitude to West Branch Forest Preserve. For now I have a sense of what is happening in the northern edge of this species’ range, but I will continue to monitor them for changes, and to continue seeking that northernmost population in the region.

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.

Swamp Cicada Confirmed

by Carl Strang

Two years ago I was positive that I had heard swamp cicadas at Springbrook Prairie Forest Preserve, and posted about it in this blog. The habitat and song were right. However, I had not seen any of them, failed to hear any when I checked the site last year, and doubts developed as I noticed how percussive are some songs of Linne’s cicada, our most common summer species. On Saturday morning I returned to Springbrook for another try (this cicada is mainly a morning singer). I heard a distant cicada that sounded right, and made my way to a pair of small isolated mulberry trees.

They were in a dry location elevated above the stream that was converted from a straight ditch to a proper meandering configuration a few years ago.

I came in too quickly and the cicada flushed, but he simply flew to a new perch higher in the same tree. He resumed singing, and I was able to get a good binoculars view. The swamp cicada, unlike most of our members of genus Tibicen, is physically distinctive. It is largely black, with some green about the head and brilliant white spots on the sides of the abdomen. I was able to confirm the identification, and brought out the camera.

Not the sharpest photo, but sufficient to document the identification.

As singing cicadas often do, he changed his location slightly every few songs.

Here’s a side view. Note that he has lowered his beak.

I was able to get good recordings of the songs, too. I feel confident now that I can identify this species by song. It is based on a pulsing vibrato like that of Linne’s cicada, but is distinctively percussive. Though some individual Linne’s have a hard quality to their vibrations, it is not as sharp, and the sound quality is different. To my ear, the swamp cicada’s song is reminiscent of a rapidly struck tambourine. You can hear an example at the Songs of Insects website.

The significance of this is that the swamp cicada is not supposed to occur this far north in Illinois, though it does so farther east. The swamp cicada joins other species including the broad-winged tree cricket, jumping bush cricket, and round-tipped conehead as singing insects that have extended their range to the north in recent decades. Note: older references give chloromera as the species name for the swamp cicada, but more recent ones have been calling the species Tibicen tibicen.

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.

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.

Meadow Tree Crickets

by Carl Strang

Some tree crickets live in trees, others live among the trees in the forest understory, but there are a few species that inhabit meadow and prairie areas. Last week I looked at some of these when I did some sweep sampling in two locations. The first was Springbrook Prairie Forest Preserve.

This low area dominated by big bluestem grass was part of the habitat I surveyed.

I went there in hope of finding more of the cicadas, tentatively identified as swamp cicadas, that I heard there last year. At the time the song seemed definitive, but I since have learned that Linne’s cicadas sometimes have songs that are similar, and so I was hoping to find one to photograph. All was quiet, however. That’s not necessarily a bad sign. If this is indeed a new population (DuPage is north of the published range for swamp cicadas), they might not be emerging every year. In any case, while I was waiting for singing cicadas I did some sweep sampling, and turned up several tree crickets.

Here is one of the individuals I caught in a goldenrod-dominated area. It has a dark stripe down the top of the head and pronotum, as well as dark antennae. Despite the otherwise pale color, these features point to the black-horned/Forbes’s pair of tree cricket sibling species.

Proper identification of these tree crickets requires an examination of spotting on the basal two antenna segments.

Here the spots on the first, basal segment are very large and smudged. Those on the second segment likewise, to the point where the entire segment looks black at first glance. Also note the dark area on the underside of this tree cricket’s abdomen. All these features point to black-horned/Forbes’s.

The next cricket, from the big bluestem area, is much paler, and shows a different antennal spot pattern.

Here the spots all are smaller, and the outer ones on the basal segments are round and have smeared edges. This is a four-spotted tree cricket.

Another Springbrook tree cricket was more ambiguous.

This individual happily nibbling my finger shows spotting that falls within the range of overlap for four-spotted and black-horned/Forbes’s tree crickets. The most definitive spot is the outer one on the basal segment. It appears just large enough to rule out four-spotted.

The next day I did some sweep sampling at Mayslake Forest Preserve.

The sample included several pale tree crickets like this.

The cricket in that last photo had the following spot pattern.

This is a clear indicator of four-spotted tree cricket, the outer spots on both segments small, round, and faded looking.

A final example showed even fainter spots.

Again I identified this one as a four-spotted tree cricket.

There is a fourth meadow species that I have been watching for but so far have not found. The prairie tree cricket is generally pale, like the four-spotted. Its antenna spots are heavy and close together, but without the blurred smudging of the black-horned/Forbes’s species pair.

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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