by Carl Strang
My best Thanksgiving wishes for you and yours.
by Carl Strang
My best Thanksgiving wishes for you and yours.
by Carl Strang
In earlier posts I outlined the major results of my study of periodical cicadas in DuPage County, Illinois. Human history has played a huge role in determining both where the cicadas occur and where they are absent. In this installment (I anticipate one more for the future) I want to pass on my observations from the 2007 emergence in some areas outside the county, and to account for the three species of 17-year cicadas.
The periodical cicadas I had observed in the off-year emergence of 2003, and the few I found in 2006 (Oops! cicadas I call them), all belonged to one species, Cassin’s periodical cicada (Magicicada cassini). One other species had been observed abundantly in northeast Illinois according to published studies, so I expected to find Linnaeus’ periodical cicada (M. septendecim) in 2007. A third species, the little periodical cicada (M. septendecula), is regarded in the literature as a more southern species, but it is less known than the others and I hoped to find it locally, too.
What I described in earlier posts applies mainly to the Cassin’s species. Linnaeus’ periodical cicadas occurred in all the areas of abundant emergence, but as a rule were less common than Cassin’s, and intriguingly their outermost song choruses consistently were about 100 meters back from the edge of the emergence area defined by Cassin’s.
I did not find the little periodical cicada at all. Not only was it absent from DuPage, but I failed to find it in what seemed like the most promising place in the state. The literature points to Livingston County as the one location from which the little periodical cicada is known in Illinois. That is mainly an agricultural county, but it does have a significant site, Humiston Woods Nature Center, which is forested and has a large area dominated by shagbark hickory, supposedly one of that cicada’s preferred nymphal food trees. On two trips to Humiston Woods I found Cassin’s and Linnaeus’, but no little periodical cicadas. Their songs are distinctive enough that I doubt I could have missed them if they were there.
As for other counties, there were abundant reports of cicada concentrations in the portion of Cook County east of DuPage, as well as the Palos area to the southeast. I found only a very few scattered individuals in parts of Cook north of DuPage County. Along the Fox River to the west, in Kane County, I found none, but did hear a report of at least one location away from the river where they were observed. I drove south along the Fox River one Sunday morning, spot checking likely forested areas, but did not find periodical cicadas until I was within a couple miles of the Fox’s confluence with the Illinois River, near Starved Rock State Park. That was surprising. Also surprising was the limited distribution of cicadas in the parts of north Will County (south of DuPage) that I checked. I found plenty along the Des Plaines River just downstream from DuPage County, at Keepataw Forest Preserve, but none at Veterans Woods just a short distance farther, nor at Isle la Cache, nor at Hammel Woods on the DuPage River. They were at McKinley Woods on the Des Plaines, and at the southernmost part of the DuPage River. Though I did not investigate further, I suppose that agricultural history has played a role in this patchy distribution, as it did in my county.
In the final installment of this series I will touch on high points of the periodical cicadas’ behavior. They provided one more big surprise…
November 24, 2008 at 12:27 pm (botany, plant-eating insects)
Tags: ermine moth, euonymus, Euonymus obovatus, herbivory, Meacham Grove, population dynamics, trailing strawberry bush, Yponomeuta multipunctella
by Carl Strang
Trailing strawberry bush is a beautiful, uncommon woody plant in DuPage County forests where there has been relative long term protection from fire. It is a native member of the genus Euonymus, E. obovatus to be exact, a close relative of the popular winged euonymus (problematic invader in native woodlands) and wahoo (a better choice, as it’s native) of landscape design. Despite its diminutive stature, E. obovatus is recognized as a euonymus by its green stems, opposite leaves and distinctive flowers and fruit. Healthy stems can stretch up to a foot above the ground, but it mainly grows horizontally in colonies that can spread over more than 50 square meters, though usually much less than that.
Caterpillars of the ermine moth Yponomeuta multipunctella are specialist consumers of euonymus leaves. They are small, the moths perhaps half an inch long, but the caterpillars live in colonies, collectively spinning webs among the foliage, and together can defoliate patches of the euonymus. I began studying the interaction between this moth and plant in 1983 at DuPage County’s Meacham Grove Forest Preserve.
When I first collected data in 1983, the ermine moth population was rapidly increasing in the many and often large Euonymus colonies. Defoliation in subsequent years, with a peak in 1985, resulted in decimation of the Euonymus and population collapse of Yponomeuta, which nearly were gone by 1987. After a hiatus I returned to the study in 1998, and found that a slow recovery by Euonymus had begun. In 2000, with Euonymus still well below its 1983 abundance, Yponomeuta reappeared in significant numbers, and sustained them in 2001, but not nearly at the levels I saw in the 1980s. In 2002 they were practically gone again. I have not seen them or signs of their presence since that year.
Nevertheless, Euonymus recovery has been slow at best, in part because it was decimated so drastically by the ermine moth caterpillars. The median product of patch length and width in 1983 was 9.5 square meters, in 2008 was only 1 square meter. In recent years there has been some browsing by whitetail deer and possibly eastern cottontails. A managed burn of the leaf litter in the understory of my study area last year appears to have had a mixed impact on the plants. Some trailing strawberry bush patches clearly were hurt, but others showed good growth this year, possibly because they were hurt less by the fire than were their competitors.
Euonymus obovatus has produced no fruit in study colonies since 2002, and there has been some attrition of the reduced patches in recent years. Larger patches continue to hold their own, though, with some continuing to show slow growth.
by Carl Strang
That is, unidentified flying Odonata. I have been studying dragonflies and damselflies for most of a decade, now, but this year I continued to find species I had not noticed before. One technique that helped was to take ridiculously distant telephotos, blow them up and look for clues that would help in identification. The results reminded me of the fuzzy photos of UFO’s that have circulated for decades. Heck, I remember reading a book on the subject when I was a kid, ogling the grainy pictures that looked suspiciously like pie plates and the like. But I so wanted to believe…
Getting back to today’s subject, I want to share photos of three species from this past season. The first is of a species I had noticed for two successive seasons patrolling a particular sunlit bend of Salt Creek at Fullersburg Woods Forest Preserve (DuPage County, IL). It clearly was a darner of some sort, and not the common green darner, but I was determined this year to take the time to try to identify it. It never landed, but attempts to track it with binoculars eventually gave me enough details to identify it as a Cyrano darner. Later, I photographed another darner well downstream from that hairpin turn. The result is blurry, but even so you can clearly see the shelf-like schnozz that gives the species its name. That photo confirmed for me that there is a population of these guys at Fullersburg, with a minimum of 5 males eventually recognized.
The next photo, also from Fullersburg, was a desperate attempt to get any kind of image of a distant dragonfly that, like the Cyrano, appeared to be a darner. This one was foraging over a mudflat near a large pile of drift logs in a pool of Salt Creek. The photos gave impressions, but few details. Nevertheless I am fairly confident of the ID. Notice the unusual brown and tan color scheme of the body. Also, the leading edge of the wing seems to have pale spots that appear in a photo of the fawn darner in James R. Curry’s Dragonflies of Indiana.
Finally, I spent a lot of time watching a couple emeralds (emeralds are a group of dragonflies) at Songbird Slough Forest Preserve on August 30. They were dark, and were the size and had the behavior of prince baskettails, but they lacked the dark spots I am accustomed to seeing on the wings of that emerald species. After a lot of tries I eventually got a UFO-type photo of one. I looked at all the descriptions of dark emeralds in my references, but none really fit the physical features, habitat, range and behavior of the insects at Songbird Slough. I was forced to conclude that these were prince baskettails after all. Later, dragonfly monitor program coordinator Craig Stettner confirmed this identification in my mind when he said he has noted that the spots of prince baskettails often are small or even missing in late season individuals.
by Carl Strang
This is the third entry in a series describing the periodical cicada emergence of 2007 in northeast Illinois. In the introductory entry I referred to an off-year emergence in 1969, four years before the main 1973 arrival. Henry Dybas of the Field Museum compiled reports from DuPage and adjacent counties that indicated large numbers of the insects appeared in many communities in 1969. In general only a portion of the local cicada populations came out early, and he expected them to be consumed by predators before they could produce enough eggs to result in an ongoing off-year splinter population (or, to use a term coined by cicada specialist Gene Kritsky, “shadow brood”).
Newspaper accounts, and observations by Illinois entomologist Phil Nixon, demonstrate that good numbers of cicadas emerged in the subsequent off years of 1986 and 1973. There apparently is not enough documentation of reproduction to confirm that this is a continuing shadow brood rather than fresh subgroups of cicadas emerging 13 years after the main emergences each time. This is such a rare event across the range of periodical cicadas that it seems more likely that the original 1969 shadow brood has maintained itself, reverting to a 17-year spacing and reproducing enough to maintain itself, at least so far. But we cannot entirely rule out the possibility that there is something different about parts of the Chicago area, or about the cicadas that live here, that prompts unusual percentages of early emergences each generation.
We do not know what prompted the shortened lifespan of these insects. Underground competition is one possibility. Something strange about the rhythm of flow in the tree sap annual cycle between 1956 and 1969 might have thrown their count off. The mechanism is not entirely mysterious, however. Each northern species of 17-year periodical cicada has a counterpart 13-year species in the South. Researchers Jo Ann White and Monte Lloyd found that there is a simple developmental difference between the species in each pair. The northern ones go into a 4-year dormancy early in their development, then snap out of it and resume growth on the steady schedule. Something made some of our Chicago-area cicadas act like southerners, skipping the dormancy.
So far all of this is old news, and except for the fact that I observed some of the 1973 cicadas myself, what is my rationale for including it in my inquiry blog? The reason is a mysterious hole in the distribution of cicadas I observed in 2007. Two adjacent DuPage County communities, Wood Dale and Addison, had essentially no periodical cicadas last year. This was unexpected, as they were on Dybas’ list of communities with cicadas in 1969, and they are adjacent to cicada rich Bensenville. They should have contributed to the third lobe of the main cicada emergence along the northernmost of the three commuter railways mentioned in my introductory entry on this subject.
I have interviewed a number of people who live or work in that area, and looked at old newspapers. There were plenty of cicadas in both towns in 2003. I have come to the tentative conclusion that in their area it wasn’t just a portion of the local population that emerged in 1969 but rather the bulk of it. So few were left for the main emergence that Dybas’ prediction of predator elimination ironically may have come true, wiping out that correct-year emergence group, so that essentially only the shadow brood remains in Wood Dale and Addison two generations later.
If I am still around in 2020, I intend to repeat my mapping of periodical cicadas in the county, this time to document what appears to be an ongoing local shadow brood of the insects.
by Carl Strang
The best place for wildlife on this year’s Canada trip proved to be the relatively remote Nagagamisis Provincial Park. Forests again were diverse, this photo highlighting a group of white spruce.
When I arrived I found the park quiet, and saw no one. I parked and was walking around looking for a campsite when I looked ahead and saw a coyote-sized gray animal leaving the road and going into the brush, but it had no tail and its hindquarters had a crouchy look: a lynx! I walked to where it had left the road and found it sitting there looking at me almost within arm’s reach. It was so surreal that I told it out loud to “wait here,” and went back to the car to get my camera. Looking back I saw that it had come back out on the road and was following behind me. It was shy when in the open on the road but calmed and sat as soon as it got off the road. Then it was gone.
Later I talked to the campground manager, who said there had been a number of reports about this animal over the summer though he hadn’t seen it himself (I suspect he only goes through the campground in his pickup). It, and the camp red fox, have not been problems for campers. He thinks the lynx may be attracted by the “partridge” (ruffed grouse).
I encountered the fox on my afternoon walk, sound asleep in an empty campsite.
In the middle of the afternoon I saw that the fox had shifted his snoozing location to the center of the sun-warmed campground entrance drive. Clearly a slow day at Nagagamisis.
In the evening I heard a commotion below my lakeside campsite. I crept through the trees and found a large flock of common mergansers. Their squabbling throaty vocalizations were reminiscent of the calls of ptarmigans from my Alaska days.
Tomorrow: A mystery in the wake of the 2007 periodical cicada emergence.
by Carl Strang
Though my trip to Canada had as its primary goal an exploration of the route of the Lake Michigan lobe of the Wisconsin glacier, an old wildlifer like me was not going to ignore the vegetative communities and wildlife along the way. I was especially interested in what I would find in the highway loop through Timmins and Hearst, Ontario, as I had never been in that area before. It’s far enough north that I passed a sign marking the watershed for rivers flowing north to the Arctic Ocean and those flowing south.
Potholes Provincial Park along Highway 101 had a little trail going to some beautiful places. The trees along the edge of this photo are black spruces, a tree of special interest because we found a couple cones of this species in the mastodon dig this summer (more on that in future posts). Black spruce was the dominant tree in many places this far north, though it no longer occurs closer to Illinois than central Wisconsin.
Kettle Lakes Provincial Park has a great trail system. Here are some photos showing a segment through paper birch,
another past savanna-spaced pines,
a closeup of lichens and a club moss.
There were edible blueberries,
asters still flowering in September
but the changing colors of plants such as these honeysuckles revealing the season.
Signs of animal life included a beaver lodge in every little lake,
dew-highlighted spider webs,
and a spruce grouse.
Tomorrow I’ll conclude with wildlife at Nagagamisis Provincial Park.
by Carl Strang
In early November I moved my office from Fullersburg Woods Forest Preserve to Mayslake Forest Preserve. The distance of the move was only a couple of miles, but what a difference in ecosystems! Fullersburg is larger, almost entirely forested, with Salt Creek winding its way through the heart of the preserve. Mayslake is more of a mix, with savanna, brush land, prairie, meadows, two lakes, a tiny stream, and a couple small marshes. And then there are the buildings and their grounds.
My office now is in an honest-to-God mansion. The mansion was built by Francis Stuyvesant Peabody, the coal mining magnate whose enterprise was the target of the wrenchingly beautiful John Prine folk song, “Paradise.” Peabody was so concerned about possible reprisals by his foes that he built a secret escape passageway within the walls of his new home. He died shortly after the mansion was completed, victim of a heart attack while riding on a fox hunt on his property.
OK, so what does all of that have to do with nature inquiry? That’s my young inner voice asking. When I was a young scientist I was committed to field work and skeptical of the theoretical side of ecology. Nevertheless, I was thinking in abstract terms of Ecological Principles and pristine ecosystem function removed from the influence of human beings.
Over the years I have changed my focus radically. Now I think in terms of the particulars of organisms and of landscapes. I also see wild lands more completely. There are no pristine ecosystems free of human influence (in an earlier post I showed how periodical cicada distribution in DuPage County was influenced by railroad history, of all things). But rather than bemoan this acknowledgement, I choose to embrace it. That acceptance flows in both directions. On the one hand, the human history of an area is interesting, and needs to be known to understand its present day dynamics. At the same time, we are a part of the ecosystem, there is no “nature” over there apart from “us” over here.
I had a blast tracing the human history of Fullersburg, and I look forward to learning more about Mayslake’s past. I’ll be sharing discoveries from both places in future posts.
by Carl Strang
This is the third installment describing my 2008 vacation to look at the route followed by the Lake Michigan lobe of the latest (“Wisconsin”) glacier. I followed the highway northeast to Timmins, Ontario, and camped a couple nights at the nearby Kettle Lakes Provincial Park. This is an area where the bedrock is covered by glacial drift and outwash, as is the case in DuPage County. As I explored the park’s trails I was struck by how familiar the outwash looked. The colors and proportions of little stones seemed very similar to ours, except for the absence of the Devonian shale and the Niagara dolomite. Those would not be expected, because they are from the bottom of Lake Michigan and from its rim, well downstream from Ontario on the glacier’s route.
The story was different at Nagagamisis Provincial Park, which I reached after driving far enough northwest that I was northeast of Lake Superior. The drift stones at Nagagamisis had different colors in different proportions and did not look familiar. This is intuitive rather than a quantitative measurement, but I feel pretty confident about it. There were plenty of basalts, but a higher proportion of white granites, and few red granites and gneisses. The surprise was that there was a presence of Paleozoic sedimentary pieces, including fossils. When I examined the maps I found that the glacier indeed had passed over an area of Paleozoic bedrock that lies between Hudson Bay and Nagagamisis.
A couple days later I camped on the shore of Lake Superior at the Agawa campground of Superior Provincial Park. The stones on the beach there were dominated by reddish granites and black basalts or diabases. There were pale quartz pieces, but little or no sedimentary rock. The high proportion of red granites, a significant percentage of which were mixed with greenstone minerals, was surprisingly unlike what we see in DuPage County. I would have thought this spot was in the path of the Lake Michigan lobe, but that appears not to be the case.
My next examination of drift was at Whitefish Point, near the tip of the Upper Peninsula of Michigan on the Lake Superior side. Here the rock mix was, to the eye, familiar and like that of NE Illinois. This spot seems unavoidably in the path of the Lake Michigan lobe.
A final stop, at Illinois Beach State Park, was similar except that the local Paleozoic stones were back in the mix.
This all was satisfying, though my tentative conclusions don’t withstand close scrutiny. A quantitative and perhaps chemical examination of the rocks would be necessary to nail it down. However, my observations are consistent with mapped glacial scratches on bedrock. It appears to me that the Lake Michigan lobe passed through or near Timmins, on the one (S or SE) side, and Whitefish Point and Door County on the other (N or NW). One test of this idea I intend to make in a future inquiry will be to search for drift on the U.P. west of Whitefish Point. I would expect to find, somewhere, a match to Agawa Bay.
There will be one final entry in this series, focusing on the biology of the part of Canada I explored on this trip.
by Carl Strang
In my earlier description of the 17-year cicada emergence in northeast Illinois, I showed how the periodical cicadas appeared in large numbers in parts of eastern DuPage County that either (1) were well forested for a long period of time; or (2) were associated with the rail lines where communities of Chicago commuters built up early, establishing urban forests that allowed the spread of the insects from source forest areas. Below is a map of presettlement DuPage, and it shows that potential source forest areas were as much a presence in western DuPage as in the eastern half of the county.
So, why weren’t cicadas there as well in 2007? My inquiry into this question took me to three kinds of sources: old newspaper accounts, old county atlases and other historical books, and a series of aerial photos covering the entire county in 1939.
Here are some quotes from the Wheaton Illinoian newspaper. Bartlett, 1888: “The locusts are singing so loud we can’t hear the frogs.” Turner Junction (now West Chicago), 1888: “The locusts are in full battle array, and will soon get in their work.” Downers Grove, 1888 (eastern DuPage, but a worthy quote): “If it’s locusts you want you can have them by the scoop shovel full.” Wheaton, 1905: “There is no longer any doubt about this being the seventeen-year locust date. They are hatching out in countless numbers.” None of the west DuPage towns had cicadas emerging beyond a handful of scattered individuals in 2007. Clearly they once were there.
So, I followed the 18 significant forest areas of the original land survey, measuring how they changed from their 1840 size to their size in the 1874 county atlas to the 1939 aerial photos to their size today. The pattern was dramatic, and clear. All forests were cut back for agriculture and development, but the process was delayed and less dramatic in eastern DuPage County where there was an earlier transition from agriculture to a suburban landscape. Chicago and the railways made the difference. By the time the eastern forest blocks were significantly diminished, the urban forests had grown and the periodical cicadas had spread into them.
In western DuPage County, the forests were cut back severely before urban forests of any size could grow, and before lands were protected by forest preserves and parks. County wide, the median forest depletion was 33% by 1874, 70% by 1939, with the greatest impact in western DuPage. I looked at the bottlenecks, the smallest known sizes to which the forest areas were trimmed since 1840, and compared them for presence and absence of cicadas in 2007. Forests that always have remained above 62 hectares in size all had cicadas. Forests that at one time or another were reduced below 50 hectares all were lacking cicadas. Between those sizes, there were 3 forest areas. Two of them had cicadas, and were relatively close to other forest remnants that had cicadas in 2007. The third, which had only a handful of periodical cicadas, was an isolated 7.7 kilometers (nearly 5 miles) from the nearest forest with cicadas.
So, now we have an accounting for the distribution of periodical cicadas in the county. Understanding them required a study of presettlement conditions, railroad history, suburban history and agricultural history.
But that is not the whole story. There were more surprises in 2007, and I will get into them in future entries.