Literature Review: Arthropod Evolution

by Carl Strang

If you’re a bug nerd you’ll enjoy the following notes on research from 2013. Especially significant were studies of butterflies and moths, and an eye-opening paper on periodical cicadas. This concludes my literature review until next winter.

Butterflies and moths had their origin in the Triassic Period according to recent studies, though the first ones were more like caddis flies than like this red-spotted purple.

Butterflies and moths had their origin in the Triassic Period according to recent studies, though the first ones were more like caddis flies than like this red-spotted purple.

Zhang, W, et al. 2013. New fossil Lepidoptera (Insecta: Amphiesmenoptera) from the Middle Jurassic Jiulongshan Formation of northeastern China. PLoS ONE 8(11): e79500. doi:10.1371/journal.pone.0079500  They found 15 species of early moths representing at least 3 families in Chinese deposits, and details of wing venation led to the conclusion that the Lepidoptera (moths and butterflies) diverged from the Trichoptera (caddis flies) by the early Jurassic Period.

Wahlberg, N, CW Wheat, C Peña 2013. Timing and patterns in the taxonomic diversification of Lepidoptera (butterflies and moths). PLoS ONE 8(11): e80875. doi:10.1371/journal.pone.0080875  They estimated timings of major episodes of speciation in the major groups of butterflies and moths. Their results point to a Triassic origin of Lepidoptera, around 215 million years ago. The timing of diversification episodes at least in some cases corresponds to times when plants were diversifying, and also after the end-Cretaceous mass extinction. Coevolution of lepidoptera with their larval food plants appears to be an important theme. They give origin ages for major Lepidoptera groups (in millions of years ago): Gracillarioidea 120, Yponomeutoidea 117, Glechioidea 106 (these first three are small moths, many of them leaf miners), Papilionoidea 104 (butterflies), Pyraloidea (including many local pyralid moths) 93, Bombycoidea (including sphinx moths) 84, Geometroidea (including inchworm moths) 83, Noctuoidea (the enormous owlet moth group) 82, Tortricoidea (including leaf-folding caterpillars) 68. All these groups are represented by local species.

The Chicago region’s 17-year periodical cicadas: Magicicada septendecim, left, and M. cassini.

The Chicago region’s 17-year periodical cicadas: Magicicada septendecim, left, and M. cassini.

Sota, Teiji, Satoshi Yamamoto, John R. Cooley, Kathy B.R. Hill, Chris Simon, and Jin Yoshimura. 2013. Independent divergence of 13- and 17-y life cycles among three periodical cicada lineages. Proc. Nat. Acad. Sci. 110:6919-6924. They sequenced a number of genes from nuclear and mitochondrial DNA from all known species and broods, and estimated divergence times based on general research that has been done on insect mitochondria. There are three species groups (referred to as Decim, Cassini, and Decula), each of which contains northern 17-year species and southern 13-year species. In any location, the species in the different groups emerge at the same time. The results clearly separated the three groups, and tied together the species within each group (e.g., 13-year Decim are more closely related to 17-year Decim than to 13-year Cassini). Furthermore, each species group is divided into eastern, central and western genetic clusters (this pattern has been documented in other organisms as well; for the most part, Illinois cicadas are in western clusters, Indiana ones in central clusters). Each cluster contains both 13- and 17-year species, “suggesting that life cycle divergence occurred independently in the three regions.” Analyses estimated that the western Cassini divergence of 13-year and 17-year species took place 23,000 years ago, 10,000 years for Decim. Population sizes for both Decim and Cassini groups appear to have been small during the last glacial period, but expanded greatly starting 10,000 years ago. The sequence appears to have been allopatric speciation of the 3 ancestral species, with the species later becoming sympatric and independently splitting into 13- and 17-year cicadas. “Surprisingly, however, the divergence of 13- and 17-y cicadas was asynchronous among the species groups and occurred repeatedly even within a species group.” The implication is “that the three Magicicada groups shared multiple refugia during the last glacial maximum.” The 13-/17-year splits occurred after the last glacial maximum, within the last 23,000 years, “suggesting that the life cycle divergence in Magicicada is closely associated with global climatic fluctuations and shorter growing seasons in the north versus the south.” However, the species groups themselves separated in the Pliocene, and their shared long lives suggest that this did not originate because of glacial climate influences. This shifting between 13- and 17-year life cycles suggests a common genetic basis among the species, and indicates a somewhat plastic nature of this trait. The coordination among species at a given location seems best explained by the selective advantage of low numbers of an invading species into the range of another, surviving best when sheltered by the established species’ numbers.

Zhao, Z, et al. 2013. The mitochondrial genome of Elodia flavipalpis Aldrich (Diptera: Tachinidae) and the evolutionary timescale of tachinid flies. PLoS ONE 8(4): e61814. doi:10.1371/journal.pone.0061814  Their genomic study traced the evolutionary relationships of the parasitic fly family Tachinidae, and molecular clock analysis calibrated to the fossil record points to the middle Eocene as the time of the family’s origin.

Brewer, MS, and JE Bond. 2013. Ordinal-level phylogenomics of the arthropod class Diplopoda (millipedes) based on an analysis of 221 nuclear protein-coding loci generated using next-generation sequence analyses. PLoS ONE 8(11): e79935. doi:10.1371/journal.pone.0079935  They place the ancestral millipedes at 510mya (million years ago), with major groupings established by 200mya.

Lucky, A, MD Trautwein, BS Guénard, MD Weiser, RR Dunn. 2013. Tracing the rise of ants – out of the ground. PLoS ONE 8(12): e84012. doi:10.1371/journal.pone.0084012     A phylogenetic analysis points to soil rather than leaf litter as the nesting habitat for the earliest ant species.

Sound Ideas: Greenstriped Grasshopper

by Carl Strang

With the arrival of spring it is time to conclude this winter series. Plenty of sound recordings remain to be shared, so I’ll resume Sound Ideas in November or December. The appropriate finale is a recording of the first singing insect we hear each year in the Chicago region, the greenstriped grasshopper. Given the late spring, I am not expecting the first of these before mid-May. I have not found a recording of this species elsewhere:


Male greenstriped grasshopper

Male greenstriped grasshopper

The buzzing sound is the rattling of the male’s wings (crepitation) during short display flights. If you have the volume turned up you may get the impression that this is a loud sound, but it is not. Though it is easy enough to hear, you may well miss it if you are not paying attention to the sounds around you. This common grasshopper occurs wherever there are abundant tall grasses, including open wooded areas, though the greatest densities are in meadows and prairies.

The female gives the species its name, though I have read that occasional brown females or green males have been observed.

The female gives the species its name, though I have read that occasional brown females or green males have been observed.

This is our earliest singer because it overwinters as a nymph, and so can complete its maturation early in the season.

Sound Ideas: Early Season Katydids

by Carl Strang

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.

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

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.”

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.

Sound Ideas: Say’s Trig Variations

by Carl Strang

As I listen for singing insects in the summer, at this point I recognize nearly all that I am hearing. Sometimes I hear something that obviously is new and different, as was the case with the green-winged cicada last summer, and I put in the effort needed for an identification. Sometimes a sound is so rarely heard that I am inclined to pass it off as an anomalous sound from a familiar species, though I store it in memory in case it turns up again. Today’s story is a case in point. On a couple occasions last summer I heard songs with the pattern of a confused ground cricket, brief trills with brief spaces between them, in a fairly regular rhythm. The problem with this was that the singers, which I was unable to see, seemed to be above the ground, and they were in wetland edges rather than upland woods. The sound quality was similar to that of Say’s trig, and I figured that this might be an alternate song of that species.

Say’s trig is a common small cricket.

Say’s trig is a common small cricket.

The typical song of this species has been well described as a “silvery trill.” Here’s a recording:


As I dug through my past recordings, I was surprised to find that the one I had made of a temporary captive in my house had the interrupted pattern:


There was no question of the singer’s identity. I also found a field recording of this pattern, at Fullersburg Woods near Salt Creek:


In this example the rhythm is less regular, and leads in the end to an extended normal trill. I am not finding a reference to this interrupted version of the song in the literature I have. It could be a context-driven alternative, or possibly individual variation. I’m certainly not prepared to suggest a different species, though new species in this genus continue to be sorted out.

Sound Ideas: Common Ground Crickets

by Carl Strang

There are 3 species of ground crickets that occur throughout the Chicago region (I still lack 2 county records for one of these, but expect to make up that deficit on a future Wisconsin trip). The ground crickets are the LBJ’s of singing insects (birding jargon: “little brown jobs” refers to sparrows, wrens and the like which are quick to vanish before they can be identified). Most ground crickets look identical at first glance, are tiny, and usually are brown. I’ll begin with the striped ground cricket.

The stripes are clear on this female striped ground cricket’s head.

The stripes are clear on this female striped ground cricket’s head.

This is the weediest of the ground crickets, first to show up in disturbed sites, and abundant in lawns. Its song consists of separate brief rough buzzes, continuously produced at 2 to 3 per second. It is low enough in pitch to hear easily, with most of the buzz’s sound range below 7 kHz. Here is a recording (complete with background bird songs and the usual traffic rumble):


The second species also occurs in open areas, but mainly where the grass is taller and vegetation better established.

Allard’s ground cricket is a close relative of the striped. The head stripes are absent, faint, or incomplete, however.

Allard’s ground cricket is a close relative of the striped. The head stripes are absent, faint, or incomplete, however.

The song consists of incessant, separate quick very high-pitched notes (6 kHz) that sound like 4-6 per second but sonographs show twice that rate. There are fairly frequent, very brief pauses (again, birds and this time a train in the background):


Now I will toss in a fourth species. The tinkling ground cricket is less widely distributed than the others (so far I have found it in half of the region’s counties), but include it here to provide a comparison to the Allard’s song. Here is a recording:


The song consists of high pitched (7 kHz) individual notes, like those of Allard’s ground cricket but distinctly slower at a given temperature (1/3 to ½ as rapidly produced). It often is rendered “tink-tink-tink…” The song is uninterrupted, lacking the frequent breaks characteristic of Allard’s ground cricket (this is especially helpful late in the season, when Allard’s often slows down). The tinkling ground cricket lives in open woodlands and woods edges, and is especially abundant on sandy soils. It looks different, too.

Tinkling ground crickets have reddish tones that distinguish them from our other ground crickets.

Tinkling ground crickets have reddish tones that distinguish them from our other ground crickets.

The final, common species is the Carolina ground cricket.

The Carolina ground cricket has faint head stripes. The female is distinguished by an unusually short ovipositor.

The Carolina ground cricket has faint head stripes. The female is distinguished by an unusually short ovipositor.

Its song is a continuous, irregularly pulsed drone, purr or trill with periods when additional pitches are added to the song, making it more dissonant. Though the sound pulses are broad enough in pitch range to qualify as a drone, it is not far from a trill, and low enough in pitch to be heard by most, at 6 kHz. Here is a recording:


As the passing geese perhaps imply, Carolina ground crickets prefer moist habitats, from wetland edges to bottomland forests. In my residential neighborhood they are fairly common, but stick to the cooler, moister foundation shrub plantings against the houses.

We’ll have to wait a while to hear these crickets again. They winter in the egg form, and need until the very end of June or, more often, July to develop to the point where they begin singing.

Sound Ideas: Coneheads

by Carl Strang

When I mention the coneheads to people unfamiliar with singing insects, the response almost always is a smile. I have to agree: one reason why the slightly musical conehead is my favorite singing insect (at the moment) is that name. Our coneheads are all katydids in genus Neoconocephalus. I have been fortunate to spend some time in the field with Gideon Ney, a Ph.D. student at the University of Missouri who is working out of a lab led by Johannes Schul that has done a lot of work with the evolution of that group. Thanks to Gideon I am aware of two species of coneheads that are not supposed to occur as far north as the Chicago region, but turn out to be at least locally common. Today I share recordings of the 6 documented species in the region. Warning: these are not delightfully musical or even (despite the name mentioned above) slightly so. We’ll ease into it with one that is somewhat pleasant to hear: the sword-bearing conehead. Its song:


That recording was made in a grassy upland meadow, typical habitat for the species, but close enough to the edge of the woods that a few common true katydids came through loud and clear. The conehead’s song is the continuous string of rasping ticks or brief buzzes. It has been compared to the sound of a sewing machine or a distant steam locomotive.

The sword-bearing conehead is named for the very long, straight ovipositor on the female.

The sword-bearing conehead is named for the very long, straight ovipositor on the female.

The next species also has a discontinuous song. The slightly musical conehead was given that name because W.T. Davis, who described it, thought it was not very loud (though he later changed his mind on that point).


The rasping sounds are easy for me to hear even with my older ears. This is a wetland species, and the males typically sing in unison.

The coneheads are named for the structure on the tip of the head, especially prominent in the slightly musical conehead.

The coneheads are named for the structure on the tip of the head, especially prominent in the slightly musical conehead.

Another species with an interrupted song is the Nebraska conehead.


The buzzes are not as rough as in the previous species, and will be heard in bushy undergrowth of woodlands, or sometimes bushes out in fields. In the southern part of the Chicago region, where the species is more common, the males sometimes sing in unison as well.

Male coneheads often sing head down. It has been speculated that the cone helps them penetrate the vegetation beneath when they are disturbed and drop to hide. Nebraska coneheads have medium sized, all black cone undersides.

Male coneheads often sing head down. It has been speculated that the cone helps them penetrate the vegetation beneath when they are disturbed and drop to hide. Nebraska coneheads have medium sized, all black cone undersides.

The remaining 3 species all have continuous buzzes. Most common region-wide is the round-tipped conehead, a katydid of meadows and roadsides.


Listen for a crackling sound in this continuous buzz.

Here the cone is short, round, and has a small black area near the tip.

Here the cone is short, round, and has a small black area near the tip.

Next is the marsh conehead, which so far has turned up only in the marshes of the Indiana Dunes parks.


The sound resembles that of the round-tipped, but comes from a wetland rather than dry upland habitat.

The cone of the marsh conehead may be all green as in this female, or show variable darkness of color.

The cone of the marsh conehead may be all green as in this female, or show variable darkness of color.

For the grand finale, here is the very loud song of the robust conehead:


This can be so loud as to be painful to the ears. It carries for long distances, as you may imagine, and is easy to hear from a car at any speed.

The robust conehead’s cone is unmarked and proportionately short. Any conehead species can come in green or brown.

The robust conehead’s cone is unmarked and proportionately short. Any conehead species can come in green or brown.

The robust conehead is most abundant in areas with dry sandy soils. Its habitat range is fairly broad, from open woodlands to prairies to corn fields.

There are at least two other species which are supposed to occur in the region, but which I have not found. Perhaps next winter I will have recordings of false robust coneheads and slender coneheads to share.

Sound Ideas: Trilling Tree Crickets

by Carl Strang

Today I wish to share recordings of 4 species of our tree crickets, which have in common songs that are continuous (rather than interrupted) trills. I will order them along a typical habitat gradient, from grasses to mixed grasses and forbs to mixed forbs and shrubs to trees (specifically, conifers).

The four-spotted tree cricket seems to prefer to sing from grass stems.

Four-spotted tree crickets are pale.

Four-spotted tree crickets are pale.

The song is a continuous clear trill:


Very abundant late in the season, Forbes’s tree cricket prefers forbs or vines.

Forbes’s tree cricket is highly variable, but usually has some dark markings.

Forbes’s tree cricket is highly variable, but usually has some dark markings.

Here is a recording from last year:


There is an interesting issue surrounding these first two songs, in my mind. I know of other singing insect students who, like me, at least sometimes can distinguish the songs of four-spotted and Forbes’s tree crickets, but we describe them with different language. To me, the four-spotted’s song has more of a clear, tone-like quality, while the Forbes’s song has a discordant tone that others apparently don’t hear. Others point to the difference in pulse rate (much faster in Forbes’s, but I need a computer analysis of a recording to tell that difference). This is the best example I have found of how describing insect songs in words can be difficult, and may in some cases be impossible.

Woodland shrubby understories to masses of forbs in open places near wooded edges are habitat for our third species, the broad-winged tree cricket. Here is its song:


Broad-winged tree crickets are distinguished by the wide wings and the raspberry coloration on the head and antenna bases.

Broad-winged tree crickets are distinguished by the wide wings and the raspberry coloration on the head and antenna bases.

To my ear, this song has a richer tone, and usually is lower in pitch than other trilling tree crickets at the same temperature.

I’ll close with the pine tree cricket, perhaps the most beautiful of the four.

The red-browns and pale greens provide good camouflage in a habitat of coniferous trees.

The red-browns and pale greens provide good camouflage in a habitat of coniferous trees.

The following recording was made indoors, from a caged male (you can hear the splashing of the aquarium pump in the background):


Again the trill is continuous and similar to the others, especially the four-spotted tree cricket, but the source of the sound in a pine, spruce or cedar (usually in a grove of them) is a dead give-away.

Sound Ideas: An Odd Trio

by Carl Strang

Today’s chapter in the Sound Ideas winter series is a recording from the evening of September 4 last year. I made it in the Miller Woods portion of the Indiana Dunes National Lakeshore. Three very different singing insects can be heard distinctly throughout:


The principal target of this recording produced the annoying, continuous buzzing sound. If you had been there, you would have remarked at how loud this insect was. It was a robust conehead.

Male robust conehead, singing posture

Male robust conehead, singing posture

This katydid has a sibling species, creatively named the false robust conehead (Neoconocephalus bivocatus). I haven’t documented bivocatus in the Chicago region, but there are a couple old possible records, so occasionally I record an individual and check the pulse rate and pattern. So far, all have been good old Neoconocephalus robustus.

The other two members of that night’s trio both produced regular, brief chirps: one higher pitched and very regular in its rhythm, the other much lower and a little less regular. The higher pitched singer is famous for the way its chirping rate varies with temperature: count the chirps in 13 seconds, and add 40 to get the degrees Fahrenheit. We know this singer as the snowy tree cricket.

Snowy tree cricket male, taking a break from singing to snack on skin.

Snowy tree cricket male, taking a break from singing to snack on skin.

That leaves the bass section. The lower pitched continuo is the product of a northern mole cricket. This swale area of Miller Woods is one of only 3 locations where I have found this species to date. I don’t have a photo to show you. True to his name, the mole cricket sings from within his tunnel, and I haven’t yet had a photo op with the critter.

Ah, yes. I see an insistent hand upraised in the back of the class. Yes? Ah, very good. Yes, there is a fourth, more intermittent performer here. Those few added chirps are a fall field cricket’s, practically ubiquitous at this point in the season, and determined to insert himself into any ensemble.

Updated Singing Insects Guide Available

by Carl Strang

Singing Insects of the Chicago Region, the guide that summarizes my survey work on this subject, now is available in its newly updated version.

Singing Insect Guide 2014 cover

This edition is pushing 90 pages, with several added species pages, an expanded section on hypotheticals (mainly grasshoppers), over 300 new county records for the covered 22 counties in Wisconsin, Illinois, Indiana and Michigan, and an expanded introductory section with topics such as conservation concerns, dispersal ability, and range extension.

This guide is available for free as a 3-meg PDF document. If you are on the mailing list you already should have received it. If you wish to be added to the mailing list (which is used for no other purpose than to forward annual updates of the guide), send a request to my work e-mail address: cstrang@dupageforest.com

Sound Ideas: Gray Ground Cricket

by Carl Strang

In the vegetation that grows just behind the beaches around the western Great Lakes you may hear a very rapid, high-pitched trilling sound, as in this recording I made at Whitefish Point (on the north side of the tip of Michigan’s Upper Peninsula) on September 16, 2009:


The area where the previous recording was made.

The area where the previous recording was made.

This interrupted trill is identical to the reference recording for the gray ground cricket on the Singing Insects of North America website. Indeed, this species is expected in open, sandy soil habitats. The only other ground cricket song I have heard that is close to this is that of the sphagnum ground cricket, which is restricted to sphagnum bogs and could not survive on sand. Allard’s ground cricket, when it occurs with the gray ground cricket, has a distinctly slower song.

The challenge for me with this species has been two-fold. First, I have never seen one. Second, I am pretty sure they occur inland as well. Here is a recording from Braidwood Dunes, a Will County Forest Preserve, September 7, 2011:


At the time I noted that there were pauses, but enough crickets were singing simultaneously that these are difficult to pick out in the recording. I have heard, and sometimes recorded, this same song in other inland locations in Kendall, Marshall and Fulton Counties. Sometimes the pauses are infrequent or nearly absent, but the songs all have a peak frequency of 8-8.5 kHz, and share similar patterns of amplitude irregularity in their sonographs. I am not aware of any other cricket that could occur in dry soils with a song like this. Furthermore, there are some mentions of inland gray ground crickets in the literature, and some authors refer to the trill as continuous. So, mainly by process of elimination I have decided to refer to all these crickets as gray ground crickets for now, but with a higher priority of catching one, particularly at one of the inland sites, for confirmation.

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