The main focus of my research these days is traveling through the 22 counties of my survey area, seeking the singing insects that live in the Chicago region. I am building on previous years’ work, filling gaps in range maps. The currency I work in thus is county records. There are around 100 species known to have occurred here, and so the maximum total would be 2200 county records. This is not going to be the eventual result, however, because many of the species live only in limited areas within the region. For instance, last week I closed the book on the green-winged cicada.
This distant photo is the best I have so far of a green-winged cicada.
I do not expect to find green-winged cicadas beyond the 10 marked counties.
They occur only in sand soil woodlands within the region. Though other counties have some areas with sand soils, I have searched them and failed to find the species. Their numbers clearly diminish at the periphery of their range. Four of these county records have been from this year.
Other species are widespread, and ultimately I expect to find them in every county. Two early season species now have filled maps as a result of my travels this spring and early summer: Roesel’s katydid, and gladiator meadow katydid.
There is learning involved in the process. Some species which historically have occurred in the area I have not yet found. Others I have found once or twice. At some point I become familiar enough with a species that I know how to find it. Then I seek it out in the appropriate habitat in the counties where I haven’t found it. The sulfur-winged grasshopper is an instructive example. This year I made a push to complete the map for this early-season species. Though I ran out of time before the end of its season, I got close.
Updated map for sulfur-winged grasshopper (open circles represent historical records)
Next year I will check sandy sites in two of the counties in Wisconsin, LaPorte County in Indiana, and Berrien County in Michigan. Though I suspect that sulfur-winged grasshoppers occur in every county, they are very few and hard to find away from sand soils. Though my own county of DuPage is marked, it is a clay soil county and over the many years I have lived here I have encountered fewer than 5 sulfur-wings in DuPage.
A final example is the northern bush katydid. I had heard two of these in the early summer of 2007, in woodlands in my county. I had heard none since. But a few days ago I went back to one of those sites and tried listening at night with the SongFinder, a device which reduces the pitch of sounds. Lo and behold, I discovered that Parson’s Grove at Danada Forest Preserve has a lot of northern bush katydids. I hadn’t realized that it was the deterioration of my hearing with age that had prevented my detecting them. Now I anticipate finding them in every county in the region.
So far this year I have accumulated 47 county records. I expect to end up with more than last year’s 174.
On September 3 I drove up to McHenry County, Illinois, to continue my regional survey of singing insects. I spent most of that hot afternoon at the Pleasant Valley Conservation Area.
This county park has some very good woodlands and savannas.
The day produced 7 county records.
My first four-spotted tree cricket in McHenry was at Pleasant Valley.
A shift to the Hickory Grove Conservation Area produced additional observations, some of them remarkable.
The most unexpected find was a small group of gladiator meadow katydids, still singing weeks after they normally are done.
The photo shows the characteristic pronotum profile and cerci. The marsh habitat and the distinctive song pattern, with the ticks finishing, rather than preceding, the buzz portion of the song all were consistent with gladiator meadow katydid. The black spots on the abdomen may be signs of a parasite load; could that have delayed the completion of development?
The same site produced this marsh meadow grasshopper.
The Lyons Prairie and Marsh, administered as part of Hickory Grove by the McHenry County Conservation District, actually is in Lake County. I followed the trail into a portion of the marsh dominated by reed canary grass. In addition to abundant slender and short-winged meadow katydids, I got an intriguing glimpse at a female Orchelimum that might have been a dusky-faced meadow katydid, which I have yet to find in Illinois. I was unsuccessful in getting a better look in that late afternoon, but at some point I need to get back there for a thorough search.
On the way back to the car I spotted this tiny grasshopper. Mature at around 3/8 inch long, it is a non-singing species, the black-sided pygmy grasshopper.
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 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.
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.
Those Tibicen cicadas, especially, characterize the sound of summer for me.
On Sunday afternoon, during a bike ride through Fermilab, I heard the first spring field crickets of the year. They had just begun, as there were only 3 of them. This is the third earliest date I have heard them in DuPage County, a little surprising given the late spring, though the deep snow that covered the ground most of the winter certainly provided the nymphs with protection. If a larger population survived, some statistical outliers could be starting up earlier than otherwise would be the case.
Cheating a little here: this is a fall field cricket female, but that species is physically identical to its spring sibling species.
Apart from such uncommonly encountered critters as sulphur-winged grasshoppers and spring trigs, the next common singing insects to mature should be the predaceous katydids (Roesel’s katydid and the protean shieldback), and gladiator meadow katydids. By then I hope that the spring field crickets will have built numbers to the point where I can finish my county survey of their distribution.
The start of the singing insect season still is a couple months away, but among the early species will be the three katydids I am featuring today. They are relatively hardy, hatching very early in the spring and developing quickly. Two of them, Roesel’s katydid and the protean shieldback, are known as predaceous katydids, and their dietary focus on animals is what allows them to get going so early. The gladiator meadow katydid is the earliest of its species group to hatch, and so the earliest to begin singing. The meadow katydids are generalists, and the gladiator probably has a greater proportion of animal foods in its diet than the others. Roesel’s katydid is a European species, introduced in the Montreal area and spreading south, east and west from there.
Roesel’s is the only katydid in the Chicago area with a color pattern anything like this.
Its song is a long, fast, constant buzz:
I am at an age where I have a little more difficulty hearing this one each year. The pitch rises with temperature, and on a hot mid-day I now need the SongFinder pitch-altering device to hear individuals that are audible in the morning and late afternoon.
The protean shieldback, like Roesel’s katydid, is a species of the meadows, but also is common in brushy areas and open woodlands.
Protean shieldback female. This is a relatively heavy-bodied katydid
Its song is an extended buzz, but has much more of a slower, rattling quality than Roesel’s song.
It is not as loud as it may seem from the recording, but is not really difficult to hear. The protean shieldback begins singing in mid- to late afternoon, and continues into the night.
The gladiator meadow katydid is similar in appearance to other large meadow katydids.
This photo shows why the meadow katydids once were known as “long-horned grasshoppers.”
The gladiator meadow katydid’s variation on the generalized tick-and-buzz meadow katydid song pattern de-emphasizes the tick portion. I often don’t notice ticks at all, though they may be softly produced more often than I suspect, as in the following recording:
The buzz is similar in quality to the protean shieldback’s song, but it is shorter in length, rhythmically produced, and the volume rises at the end.
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.”
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.
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.
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.
I hope to get back to Kendall County at least one more time this year.
Last week I made reference to Darryl T. Gwynne’s book on katydid mating system evolution. That book led me to other references, including a Ph.D. thesis by Marianne Feaver, who studied the behavioral ecology of three species of large meadow katydids (genus Orchelimum) under the direction of Richard Alexander at the University of Michigan in the 1970’s. I ordered a copy of Feaver’s thesis, and enjoyed reading it over the weekend. There was much richness of detail that will benefit my observations in the coming months and years. Here I’ll just share a few gleanings.
Male black-legged meadow katydid
Feaver studied black-legged, common and gladiator meadow katydids. Maturation in the three species required 2 months from hatching to adulthood. In northeast Illinois the earliest species, O.gladiator, matures in late June, implying a late April hatch from eggs laid in the stems of plants.
Female gladiator meadow katydid
Oviposition plants, food and cover are the three most important habitat features in these species. Upon reaching maturity, females move from nymphal areas that emphasize food and cover to places offering the best mix of food, cover and oviposition sites, and the males follow them there. The males then set up circular territories that space them out. These are defended mainly through song, though in high density populations physical combat often can take place. Defensive songs are characterized by increased number and rapidity of the tick portion of the song, the buzz portion apparently not important here. The territorial male reacts to the singing intruder, who may retreat or approach. In the latter case, after repeated warnings, the territory holder is likely to attack. The heavier male generally wins. Territory holding males tolerate silent males, which apparently are waiting for the territorial males either to be removed by predators or parasites, or to mate, after which they must retreat to gain back their weight.
Male common meadow katydid
They spend the night buried down in low, dense cover, then males begin spacing themselves out in mid-morning, and are singing by late morning. After territories stabilize, singing continues through the afternoon. Females assess and compare males, with mating taking place in the late afternoon. Females may take several days to choose a mate, however, and only mate once. In the early evening they break off to feed, then climb down into cover to spend the night.
This pattern provides a basis of comparison to other species, which will vary in detail. For instance, though I found a freshly mated female dusky-faced meadow katydid in the mid- to late afternoon, as I mentioned last week, that species reportedly does most of its singing at night.
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.
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
This bigger insect may have larger fat reserves to draw upon and so extend its season.
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.
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: firstname.lastname@example.org
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.
Last week at Blackwell Forest Preserve, the Roger Raccoon Club hiked to our usual place for tree-climbing instruction. Along the way the kids somewhat nervously were inquiring about buzzing in the tall grass beside the trail. I assured them that the source was not an abundance of rattlesnakes, but rather gladiator meadow katydids. I searched for one to show them, and the first one I found proved to be a female. I had no photos of a female of this species, and took advantage of the opportunity.
Gladiator meadow katydid, female
This species is unique among our northeast Illinois Orchelimum in the shape of its ovipositor.
Though the bottom edge of the ovipositor is curved, as is true for all females of this genus, the top edge is unique in being ruler-straight.
Of course, the fact that there is little or no overlap between the gladiator’s early season and those of other species also helps.