Cicadas East, Cicadas West

by Carl Strang

Today’s puzzle is the odd range boundaries of two cicada species that occur in the 22-county area I define as the Chicago region.

The scissor-grinder cicada (Neotibicen pruinosa) is one of the four most abundant annually-appearing cicadas in northeastern Illinois.

Scissor-grinder cicada

Though individuals may sing occasionally from mid-morning to dark, their ee-oo-ee-oo-ee songs especially dominate the wild soundscape at dusk in mid- to late summer. In the following recording, the cicada is introduced and ushered out by a nearby striped ground cricket.

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A recent review of North American cicadas (Sanborn and Phillips 2013, Diversity 5: 166-239) shows what appears to be a gap in the species’ distribution in north central Indiana. I was inclined to regard this as simply indicating a lack of sampling in that area, but this year I pushed to complete my own map for scissor-grinders. Here is the result:

Black dots indicate counties where I have observed scissor-grinder cicadas.

The numbers of scissor-grinders thin out dramatically in the eastern and northern counties of the region. I cannot find them at all in Walworth, Berrien, St. Joseph or Fulton Counties. They barely reach the southwest corner of Marshall County. Sanborn and Phillips show them picking up again farther east, but only one record each for Wisconsin and Michigan, in both cases outside my region.

There is no obvious explanation for the Indiana gap. It does not correspond to soil type, as scissor-grinders can be found in both sand and clay soil areas, and are absent from areas of both.

Swamp cicadas (N. tibicen) have a distribution mainly south and east of the Chicago region, and Sanborn and Phillips (2013) do not map them into the Illinois or Wisconsin portions of my region. My work extends that range a little, but they are scattered individuals in Illinois, with only one Kane County and one Kankakee County site.

Swamp cicada

Black dots indicate counties where I have observed swamp cicadas. Red stars show locations of the northernmost records.

Their song is a percussive vibrato. Here is a recording from southern Indiana in which several individuals provide overlapping songs:

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They occur mainly in the Kankakee and DuPage River areas in Illinois. In the southeastern portion of the region, a few can be found along the Tippecanoe River in Fulton County, but they apparently drop out before that river reaches Pulaski County, which also is well south of the Kankakee River drainage. The swamp cicada’s range boundary is a western one, but explaining it is just as difficult as in the scissor-grinder. St. Joseph County seems to be the center of abundance in the region, with Potato Creek State Park having an especially high density.

The practice of science is largely about questions, and these newly discovered odd range boundaries provide good ones for these two cicada species.

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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.

Sound Ideas: Green-winged Cicadas

by Carl Strang

One of the singing insects I have been seeking for several years in the Chicago area is the green-winged cicada (Diceroprocta vitripennis). Some references have suggested that this is an early-season species, and I thought I heard them in June of 2007 (the brief regular buzzes in the following recording, with Cassin’s 17-year cicadas in the background):

Those sounds were very similar to the cooler-temperature recording of Diceroprocta at the University of Michigan’s cicada website, though a little slower (the temperature was about 10 degrees cooler). The problem was that the periodical cicadas were in their peak year and season at the same time, and the identification was ambiguous because I couldn’t entirely rule out the possibility that these were Cassin’s 17-year cicadas warming up. Returns in subsequent years to places where I heard those sounds failed to turn up a repeat performance. Now I find that those actually were “Court III” signals of the Cassin’s cicadas, produced by the male as he connects with a female for mating.

During my survey work this past field season, I finally heard green-winged cicada songs on July 29, first at Willow Slough Fish and Wildlife Area, then at Jasper-Pulaski, both in Indiana (a scissor-grinder cicada song is in the background at the start):

Oak woodlands on sandy soils, including this one at Jasper-Pulaski Fish and Wildlife Area, are where I heard this song.

Oak woodlands on sandy soils, including this one at Jasper-Pulaski Fish and Wildlife Area, are where I heard this song.

These were a match for the warmer-temperature song at the University of Michigan website (the temperature was cooler for my recording, but the insect may have had a warm perch in the sun; I didn’t see it). That day was the extent of my experience with this species, though, so more observations are needed to get a better handle on the abundance, distribution and habitat of green-winged cicadas in the Chicago region.

Mayslake Update

by Carl Strang

Today, some accumulated photos from, or at least connected to, Mayslake Forest Preserve.

The stream corridor marsh has become dry for the second year in a row, though this time it happened a couple months later.

The stream corridor marsh has become dry for the second year in a row, though this time it happened a couple months later.

Insects provided some photo ops.

This female sword-bearing conehead was the first of its kind I have seen at Mayslake in three years.

This female sword-bearing conehead was the first of its kind I have seen at Mayslake in three years.

Scissor-grinder cicadas occur in greater densities at Mayslake than in any other place I have found them to date.

Scissor-grinder cicadas occur in greater densities at Mayslake than in any other place I have found them to date.

This short-winged grasshopper appears to be a Melanoplus borealis, but I am not entirely sure.

This short-winged grasshopper appears to be a Melanoplus borealis, but I am not entirely sure.

The backdrop for the final photo is from Mayslake, but the pine tree cricket is the one Nancy Collins sent me from Wisconsin, still singing weeks later.

The cricket’s camouflage is superb.

The cricket’s camouflage is superb.

Snow fell for the first time yesterday: time for a new seasonal transition.

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.

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

Scissor-Grinder

by Carl Strang

The Tibicen or annual cicadas are a late summer phenomenon whose loud songs characterize the August days. Occasionally you may find a shed nymphal shell or a dead adult on the ground, but generally they sing out of sight, high in the trees. Last week at Mayslake Forest Preserve I had a rare opportunity to watch one in action.

This was a scissor-grinder cicada, singing only 10 feet up in a crab. The bright white underside perhaps explains its species name, pruinosa.

The cicada was walking around in the branches, singing at frequent intervals. In this photo it apparently is feeding, as its beak is extended.

The cicada was alert and watchful. As I moved within 15 feet for a closer photo the insect abruptly stopped in mid-song and was gone.

A few days later I found a dead one on the walkway near the chapel.

I have not seen a concentration of this species anywhere to match that at Mayslake. In the evening their EE-SHER-EE-SHER-EE-SHER-EE songs can drown out everything else. (Before I learned their conventional common name I used to call them lazy-dying-battery cicadas, as their song reminded me of a car engine whose battery was on its way out. This was to contrast them with the angry-dying-battery cicada, Tibicen auletes, aka northern dusk-singing cicada, whose song also is slow but has an edge to it).

Tibicen Song Sorting

by Carl Strang

My first entry into singing insects study came when I ran across the University of Michigan cicada website in 2003 or 2004. The site includes recordings of cicada songs, and as I played them I realized that all my life I had been hearing the distinguishable songs of several species without knowing it. These were all members of genus Tibicen, and that summer I recognized three common species in DuPage County.

They look very much alike, and are hard to see when singing high up in trees, so it was well that their songs were distinctive. After a couple years, however, I began to notice that the songs I attributed to one of the three, Tibicen linnei or Linne’s cicada, had two variations and with references I was able to distinguish a fourth common species, Tibicen lyricen, the lyric cicada. The differences among these species and their songs I described in some detail in a post last year.

Recently I was reviewing a wide range of singing insects reference recordings when I realized I need to pay attention again to the songs I have been identifying with Linne’s cicada. The swamp cicada, Tibicen chloromera, has a vibrato very close in speed to linnei’s. It has, however, a percussive quality in each vibration that sets it apart from linnei’s smoother, more wavelike vibrato. I had paid too close attention to written descriptions of the swamp cicada, in both the popular and scientific literature, which imply that chloromera is found only in wetlands and sings only from low perches. In fact I am now finding that at least around Culver, Indiana, chloromera often sings hundreds of yards from wetlands, and at least as often from high trees as from perches in lower ones. I have heard them in forests as well as more open stands. This is in keeping with other Tibicen cicadas, which at least in their singing perches show wide ranges in habitat.

So far I have not heard chloromera in DuPage County. I have found that I need to listen carefully, because when lyricen are singing their first, warmup songs of the day they have a slower vibrato with a percussive quality like chloromera’s.

The two areas I frequent most, DuPage County, Illinois, and Marshall County, Indiana, have different Tibicen species lists though they are only about 100 miles apart. Both are homes for canicularis, linnei, lyricen and pruinosa (the dog day, Linne’s, lyric and scissor-grinder cicadas, respectively). So far, only Marshall County appears to have chloromera, the swamp cicada, but I don’t consider the case to be closed. Marshall County also has a sixth species, Tibicen auletes, the northern dusk-singing cicada, which is associated with sandy soils and so does not occur in DuPage County’s clays.

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