A Pause in the Action

by Carl A. Strang

In the early part of the season, from April to early July, my research focus is on those species of singing insects which matured from overwintering nymphs, plus some small early-season cicadas. This is a minority of species, as most of the crickets, katydids, and singing grasshoppers mature after the middle of July, having wintered as relatively secure eggs and needing time to grow up.

I was able to close the book on northern wood crickets last month, and the story here is a sad one. This forest-dwelling member of the field cricket group had been reported from two northern Indiana sites by W.S. Blatchley in 1903. As far as I know, no one has sought them since then in the northern part of the state. Last year I determined that they no longer occur where Blatchley found them. This year I checked the largest other eight forests in the Indiana portion of my study region. If they ever were there, they are gone now. I suspect that forest fragmentation for agriculture and other purposes is responsible for the loss. Blatchley’s detailed descriptions leave no doubt that he knew how to recognize the species.

This northern wood cricket is from the northernmost site where I know they still occur, Eagle Creek Park in Indianapolis.

I was able to close the book on another southern species, the spring trig, in June.

This tiny, early-season cricket is common in southern Indiana.

I have found a few scattered groups of spring trigs in southernmost Fulton and Jasper Counties in Indiana. A thorough search failed to turn them up in neighboring Pulaski and Newton Counties. I may check again in a few years, on the possibility that the species is expanding northward.

One positive result was finding sulfur-winged grasshoppers in the East Main Street Prairie of Cary, Illinois. This adds McHenry to the counties where I have found the species. They probably occur in every county in my region but are common only on sandy or gravelly soils such as Cary’s kame-like hills. I have learned of another candidate site which may add Fulton County, Indiana, next year.

Sulfur-winged grasshoppers are characterized by bright yellow hind wings, which they rattle in flight to produce their song.

Prairie cicadas started a little late this year. I was pleased to find that management efforts to remove brush from the West Chicago Prairie Forest Preserve near my home appears to have paid off in both rebound of diverse prairie vegetation and an increase in the cicada numbers.

Prairie cicadas, are tiny, around an inch long.

Failure to perform such restoration work has a cost. Once known to occur in Kankakee County, prairie cicadas apparently are gone from there, the prairies having been degraded by brush, teasel and other invasive plants.

A final story is that of the periodical cicadas. In each cycle since 1973, the main appearance of 17-year cicadas in Chicago’s western suburbs has been preceded by a significant, 4-year-early emergence. This happened in 1969, 1986, and 2003. I suspect that in a small part of this area, all the cicadas now have switched to the early time. If you have done the math, you realize that it may happen again next year. One predictor to watch for are what I call oops cicadas, a few individuals who jump the gun by a year, or miss the main emergence and come out a year late. As expected, this has been happening this spring. I have heard 3 individuals myself in two cities and seen photos of the insects from 3 more. Counting and mapping them will be a highlight of next year’s early field season.

I predict that some areas will have good numbers of 17-year cicadas next year.

No Shadow of a Shadow

by Carl Strang

I didn’t find any periodical cicadas out in Addison or Wood Dale this year. That might seem like a strange statement, given that our local main emergence last happened in 2007, and the next is due in 2024.

A 2007 photo of representatives of DuPage County’s two species of 17-year periodical cicadas: Linnaeus’s on the left, Cassin’s on the right.

A 2007 photo of representatives of DuPage County’s two species of 17-year periodical cicadas: Linnaeus’s on the left, Cassin’s on the right.

I had reason to think I might find a few of these amazing critters here this year (they are peaking in Ohio in 2016, by the way). For several generations, now, starting in 1969, significant numbers of the cicadas have emerged 4 years early in the western suburbs of Chicago. This phenomenon, called a shadow brood, since has been found in a few other locations in eastern North America. It generally is thought to be a one-time deal, but the repetitive nature of this local shadow brood has me thinking there has been reproduction each time. Furthermore, the cicadas in the adjacent cities of Addison and Wood Dale appear entirely to have switched to the shadow timing. Residents reported them to be abundant in 2003. I found hardly any there in 2007.

The next shadow brood emergence therefore should happen in 2020. That assumes that there was indeed reproduction in 2003, or at least that local conditions again will result in some cicadas emerging at age 13 rather than 17. Those numbers are significant, as southern broods of related cicada species always are 13-year cicadas. Something caused a switch in some of our cicadas, in 1969 at least, bumping them onto the 13-year track. If they have been reproducing, then the subsequent shadow broods have resumed the 17-year life span. If you have followed this convoluted story, then you can guess why I thought I might find a few periodical cicadas this year. If the shadow brood indeed is all that exists now in Addison and Wood Dale, and something were to cause a few of them to make the 13-year jump now, 2016 is when they would have emerged. Perhaps a few did, but if so I did not hear any singing, nor did I see any shed nymphal exoskeletons, in this year’s tour of the two cities.

I will repeat my route each year, as I have done starting in 2014. A few cicadas out of the millions emerge a year or two early. I will be very surprised if there are any next year, but the anticipation will build as I look to a possible major emergence in Addison and Wood Dale in 2020.


Literature Review: Periodical Cicadas

by Carl Strang

This week’s literature focus is on a single paper, which looked at a significant aspect of periodical cicada biology.

The northern periodical cicada species, Linnaeus’s 17-year cicada on the left, Cassin’s 17-year cicada on the right

The northern periodical cicada species, Linnaeus’s 17-year cicada on the left, Cassin’s 17-year cicada on the right

Karban, Richard. 2014. Transient habitats limit development time for periodical cicadas. Ecology 95:3-8. He studied septendecim and cassini (our two local species of Magicicada) in New York state. There are several hypotheses explaining why their development times are so long: Pleistocene historical influences (long life span buffered annual climate variation in glacial refuges), predator satiation (some early maturing individuals wait for slower ones to catch up, and long life spans facilitate this), low nutrition forces long development, and increased fecundity (17-year species have been shown to be more fecund than the more southern 13-year versions). Here he examined the possibility that habitat quality changes rapidly enough to put an upper limit on such advantages of long lifespans. Though past studies pointed to possible advantages of edge trees, here he compared weights of newly eclosed adults from edge vs. forest interiors, finding the former to be only slightly (4.9%) heavier in septendecim but no difference in cassini. He took density of emerging nymphs as an indication of habitat quality. Changes in study sites were significant between emergences, enough to limit any advantage of longer life. He commented on the Raccoon Grove study site in Will County, once one of the highest-density populations known, mentioning that they plummeted over just a couple sequential emergences, first because of Dutch elm disease killing host trees. Karban and Yang visited that site in 2007, hearing one chorus but finding no emergence holes or nymphal skins.

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.

A Little Celebration

by Carl Strang

It has been 30 years since I last published a scientific paper. My early papers were on birds and turtles, as my formal training focused on vertebrate ecology. As is clear in this blog, I have again become interested in scientific research, but now the focus is on invertebrates, specifically singing insects. The first scientific paper to result from this work just came out in The Great Lakes Entomologist. Here is the abstract:


Geography and History of Periodical Cicadas (Hemiptera: Cicadidae) in DuPage County, Illinois

Carl A. Strang1


The spatial distribution of periodical cicada (Magicicada septendecim L. and M. cassini Fisher) emergence in 2007 did not match either historical locations of woodlands or the cicadas’ own geography in the 19th and early 20th centuries in DuPage County, Illinois. Cicadas were present in forest areas that had remained above 61 ha throughout historic times, and they were absent from areas which at some point had been reduced below 52 ha by tree removal, mainly for agriculture. Isolation of forest areas also may have contributed to local extinctions. The insects have spread into new, urban woodlands created by residential plantings. Their distribution is associated with the early growth of towns along commuter railways in the eastern part of the county (toward Chicago). A peculiar gap in the main emergence area (encompassing two adjacent cities) may be the result of the cicadas shifting their emergence four years early. An active dispersal on 9–11 June, coinciding with the peak in cicada singing in forested areas, apparently placed scattered small groups of cicadas outside the main emergence area.

1Forest Preserve District of DuPage County, P.O. Box 5000, Wheaton, IL 60189-5000.

Two species of periodical cicadas were the subject of the paper. The larger Magicicada septendecim (Linnaeus’ 17-year cicada) is on the left, M. cassini (Cassin’s 17-year cicada) on the right.

Two species of periodical cicadas were the subject of the paper. The larger Magicicada septendecim (Linnaeus’ 17-year cicada) is on the left, M. cassini (Cassin’s 17-year cicada) on the right.

Most of the content of the paper I have posted in this blog in less formal terms, for instance: https://natureinquiries.wordpress.com/2008/11/12/where-the-periodical-cicadas-were/

The study isn’t done, but a few years need to pass before I can seek more information to add to the story.

A New Periodical Cicada Puzzle

by Carl Strang

I have been getting questions from people asking about periodical cicadas this year. They have been hearing reports of brood XIX, the simultaneous emergence of several species of 13-year cicadas to the south of our area. I have been giving the sensible answer that no, we won’t be getting them in northeast Illinois. That was up until Tuesday afternoon, when I heard three periodical cicadas singing on the Mayslake Forest Preserve mansion grounds.

The songs were those of Cassin’s periodical cicada. This is a photo from the 2007 main emergence in our area. The insect on the right is a Cassin’s 17-year cicada, the one on the left is our other local species, Linnaeus’ 17-year cicada.

But that wasn’t all. That same day I heard another singing cicada half a county away from Mayslake, at forest preserve district headquarters. Then yesterday I heard individuals at two more locations on the Mayslake preserve, and two in west central DuPage County, where there were very few scattered individuals in 2007. Furthermore, I have heard reliable reports of singing periodical cicadas in other DuPage County locations.

I don’t see any way to connect this to the 2007 emergence. True, a few late cicadas came out in 2008 (I called them Oops Cicadas), but that is to be expected. There were none in 2009 or 2010. The question I would like to have answered first is whether these are 13-year or 17-year cicadas. There is a 13-year species with the same song as cassini. I hope I can get specimens, a shed nymphal exoskeleton at least. That could be held for potential future DNA checking. This would establish whether these might be outliers of brood XIX. The thing is, most people don’t listen for singing insects. We don’t really know what is going on with periodical cicadas outside of peak emergence years or core emergence areas. If I learn anything new, I’ll pass it on, but I will try to get as many location observations as I can in the limited time I have to devote to this unexpected development.

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