Recent Mayslake Animals

by Carl Strang

With spring migration over and the weather lurching toward summer, the wild menagerie at Mayslake Forest Preserve has been showing some new faces.

This buck has been hanging around for a couple weeks, and may have decided to make the preserve his summer home.

This buck has been hanging around for a couple weeks, and may have decided to make the preserve his summer home.

In most years Mayslake has hosted a summer buck group, but occasionally a doe will raise her young there.

The chickweed geometer is a recent addition to the preserve’s insect list.

The chickweed geometer is a recent addition to the preserve’s insect list.

I didn’t recognize this damselfly that was hanging out with a group of smaller eastern forktails, and was able to get a photo for identification purposes.

I didn’t recognize this damselfly that was hanging out with a group of smaller eastern forktails, and was able to get a photo for identification purposes.

It turns out to be a male orange bluet. For a time after they emerge from the water, they don’t have a speck of orange on them.

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Odonata Update

by Carl Strang

This has been a remarkable spring for damselflies and dragonflies at Mayslake Forest Preserve. Carolina saddlebags have been present in unusual numbers for weeks, outnumbering black saddlebags by a wide margin.

This one posed on June 3, and they keep on coming.

This one posed on June 3, and they keep on coming.

Spring is also the time when the lakes host two baskettail species.

Common baskettails won’t be around for long. Good luck finding one perched.

Common baskettails won’t be around for long. Good luck finding one perched.

This is one of the few times I have seen a prince baskettail perched. I wonder if it needed a break in the midday sun. It seems to be semi-obelisking here.

This is one of the few times I have seen a prince baskettail perched. I wonder if it needed a break in the midday sun. It seems to be semi-obelisking here.

Friday was a remarkable damselfly day. First came the following two individuals, striking with a metallic sheen on their abdomens. I don’t think they were teneral spreadwings, however.

This one best matches the female orange bluet.

This one best matches the female orange bluet.

Nearby was this one, which I believe was an immature male orange bluet.

Nearby was this one, which I believe was an immature male orange bluet.

The best was yet to come, however. Up in the meadow surrounding the temporary off-leash dog area at the former friary site, two bluets appeared that I don’t believe I have ever seen before. The first was a blue-type bluet that was just too small to be a familiar bluet.

Ta-da! A double-striped bluet!

Ta-da! A double-striped bluet!

In a more shaded area were two foraging damselflies which proved to be male and female of another species new to my experience.

Check out the enormous eyespots and the large blue area at the tip of the abdomen. This is a male azure bluet.

Check out the enormous eyespots and the large blue area at the tip of the abdomen. This is a male azure bluet.

A female azure bluet was nearby.

A female azure bluet was nearby.

The female was using an interesting foraging technique, reminiscent of a hover-gleaning bird, slowly flying up and down and briefly hovering to scan each leaf of an erect goldenrod plant, visually hunting for resting prey. As the photo shows, she was successful.

Literature Review: Bluets

by Carl Strang

One of the papers I found most interesting in this year’s literature review had to do with damselflies (Siepielski, Adam M., Ken-Lou Hung, Eben E.B. Bein, and Mark A. McPeek. 2010. Experimental evidence for neutral community dynamics governing an insect assemblage. Ecology 91:847-857).

Familiar bluet. I can believe that this one is ecologically interchangeable with most of the others.

In particular they focused on the 34 species of North American bluets that live in lakes with fish in them (among both dragonflies and damselflies there are a few species that live only in the relatively few bodies of water in which nymphs are free of predation pressure by fishes). Using a variety of experimental, observational and comparative methods, the researchers concluded that the nymphal stages of all these species are completely interchangeable. Competition, separation into different chunks of niche space, differential avoidance of predation, none of these processes apparently separate these bluets ecologically.

Tule bluet. This species, on the other hand, in my experience sticks to the larger, more open lakes.

These bluets as a group are, however, separated from the forktails, a different group of similar-sized damselflies. Bluets are better at avoiding predators, while forktails are more efficient “at converting prey into their own biomass.” I’m not entirely sure what that means; perhaps being more predation prone, they need to be able to get by on less food and so minimize their own exposure.

Eastern forktail. The authors seem to believe that the forktails likewise are ecological equivalents. Someone needs to get the data.

If the larvae are all alike, perhaps the adults are ecologically subdivided? Siepielski et al. didn’t look into this, but they pointed out that the damselflies live in their adult stage for an average of only 4 days, compared to most of a year as nymphs. The diversification of bluet species “seem[s] to have been driven primarily by sexual selection for differentiation in reproductive structures and little else.”

Slender bluet. Another question is, why are some species much more common than others? I run into a lot more familiar bluets than slender bluets.

They suggest that similar neutral community dynamics may operate commonly among insects, given the many sibling species groups. This raised my own metaphoric antennae, as many singing insects (cicadas, crickets and katydids) belong to clusters of sibling species. Along the way, Siepielski et al. mentioned the interesting fact that dragonfly nymphs have been shown elsewhere to feed negligibly on bluet nymphs.

Orange bluet. On the whole I accept these results, but as hinted in the above captions, there may be a little more complexity to this story.

A related theoretical paper published this year (Van Doorn, G. Sander, Pim Edelaar, and Franz J. Weissing. 2009. On the origin of species by natural and sexual selection. Science 326:1704-1707) developed a model that supports the possibility of sympatric speciation where female selection of mates produces divergence. It requires the appearance of identifiers (e.g., color patches) that correlate with the different subpopulations. Females in the different environment patches then are favored to the extent that they identify and mate with the appropriate local males.

October Monitoring Run

by Carl Strang

Last weekend’s warm weather allowed me to make a late dragonfly monitoring run on the Des Plaines River at Waterfall Glen Forest Preserve. Looking back through my records, I find that in all the monitoring I have done since 2003, I never have made a formal outing in October. It was worth trying for that reason, if no other. Besides, it was a nice day to be on the river in my sea kayak. There isn’t a lot to report as far as dragonflies and damselflies go. The only dragonflies were a pair of common whitetails, the female laying some last ditch eggs. I saw a couple familiar bluets,

a few orange bluets,

a stream bluet, 3 eastern forktails and 7 American rubyspots.

The last confirmed that this species is active late in the season, supporting my sighting at Fullersburg (which at first I thought was a smoky rubyspot). I also made some singing insect observations, the best of which were jumping bush crickets singing in the early afternoon on both sides of the river. This adds to my local range for this species, which clearly has shifted north of where you will find it mapped in references. The shallow lagoon at the downstream end of my monitoring area was hosting a gathering of great egrets.

The gorilla in the room, however, was a major construction project underway on the south side of the river. A fence was being built.

With much machinery, much shouting and an impressively speedy progress (I saw no sign of this when I last was there in late August), a metal framework is being erected and filled with fine-meshed screening.

The fence is parallel to the Centennial Trail, which has been closed for this project. The fence is only 6 feet tall or so, enough to disrupt the view of trail users but not enough to be a significant barricade to wildlife, I thought. A little research on the Internet revealed the purpose of this structure. It is a fish barrier. That may seem strange, but high water levels could lift the river high enough to reach the fence. The target fish are Asian carp, a group of 4 species which have been much in the news because of concerns that they might cross from the Mississippi River drainage (which includes the Des Plaines) and the Great Lakes. The Des Plaines River is paralleled by a canal, so the fence apparently is intended to keep the carp from going between the two. Would tiny baby carp be stopped, though? I’m not enough of a fisheries biologist to judge. For more information on the fish species and other information, here is a link.

Kayak at Last

by Carl Strang

I was beginning to wonder if I would get the opportunity to put a paddle in the water this year, but circumstances allowed me to run my dragonfly monitoring route on the Des Plaines River at Waterfall Glen Forest Preserve this past weekend. Of course, in the context of this blog the monitoring is the main thing, but on a personal level it’s been hard to go almost a year without paddling. My sea kayak has taken me through north Georgian Bay.

It’s given me sights like this, Devil’s Island in the Apostles of Lake Superior.

On Sunday afternoon the sea kayak Water Strider was my vehicle yet again. I found no new species, but was interested to find that the counts for various species fell between the values for last year’s August 2 and September 3 counts, despite other measures of phenology generally placing this year earlier than last. Common whitetail and eastern amberwing dragonflies were closer to the August 2 count, though both exceeded any of last year’s counts for those species. Powdered dancers and stream bluets fell between the counts of last year’s dates. Familiar bluets were closer to the September 3 count. Many, like those in the following photo, were ovipositing.

Skimming bluets showed a significant increase, with 10 counted on this trip against 1 for the entire 2009 season. In contrast, jade clubtails were missing this time, and orange bluets were few. I wonder if their seasons are done for this year.

Dragonfly Monitoring Update

by Carl Strang

Earlier I described  my first venture into dragonfly and damselfly monitoring by kayak. I have been out on the Des Plaines River twice since then. There has been some variation in the count of species and individuals each time, but most seems unremarkable. I’ll focus on a couple high points. The biggest surprise was a transition in the damselflies. The slender bluet was the common black type bluet my first time around.

Slender bluet 5JL 1b

Bluets are a group of small to medium sized damselflies. Black type bluets are so called because their abdomens are nearly all black as viewed from above. On my second and third outings, the slender bluets were replaced by stream bluets as the common black type bluets. Here is one of the latter I rescued from the water.

Stream bluet 23JL09 1b

Note that, in contrast to the slender bluet in the top photo, the stream bluet has a slender blue shoulder stripe with a wider black stripe below it. “Eye spots” on the back of the head are smaller in the stream bluet, and there is less blue in the abdomen tip. Stream bluets were largely in tandem pairs and actively laying eggs on floating vegetation during both recent outings.

Stream bluets tandem b

The other surprise is the relatively large number of orange bluets. Here is one sharing a photo with a stream bluet.

Orange and stream bluet b

I’m not saying that the river is swarming with them, but in my experience a count of 13 orange bluets in a 2-hour outing is a lot. A final note is that eastern amberwings have become the most abundant dragonflies, despite my seeing none on the first outing. Here is a photo of one from 2007.

Eastern amberwing male 2b

I have decided to limit my monitoring to the stretch of river that bounds Waterfall Glen Forest Preserve. This gives me a span of stream between the launch ramp and the preserve in which I can practice another type of inquiry, to be featured tomorrow.

Mayslake Odonata Update

by Carl Strang

The weather has been rainy, gloomy and cool on many recent days, but when the sun appeared so did the insects. At Mayslake Forest Preserve I have been able to add new species and observations that provide a foundation for future study. Eastern forktail damselflies already have been busy laying eggs in May’s Lake.

Eastern forktails laying eggs b

Meanwhile, other damselflies are emerging. The next two photos are, I believe, of common spreadwings, a male

Common spreadwing b

and a female.

Common spreadwing female 3b

Having newly emerged, they are holding their wings together more than usual. Another spreadwing species is the slender spreadwing.

Slender spreadwing 1b

Note the contrasting pale veins of the wingtips. Another, blurry photo established that the abdomen has the characteristic length, twice that of the wings. I have seen orange bluets at both of the preserve’s lakes.

Orange bluet b

Familiar bluets also have begun to appear.

Familiar bluet b

The year’s first blue-fronted dancer was a female.

Blue-fronted dancer female b

Its abdomen is dark, including the sides of the tip, and has only a very narrow pale line down the top. Shifting now to dragonflies, I’ll start with a 12-spotted skimmer that began patrolling the stream corridor marsh in June. I expect the species to be common there. This one I photographed elsewhere in 2004.

12-spotted skimmer b

Blue dashers have been active out in the fields, and soon will be appearing at lakes and marshes.

Blue dasher female 1b

A jade clubtail has staked out a piece of the May’s Lake shore.

Jade clubtail b

Cruising farther out are the prince baskettails. Here is a UFO-ish shot of one.

Prince baskettail UFO b

And here is a common baskettail  showing the basal wingspots that are visible on some, but not all individuals.

Common baskettail spot b

A final, cautionary photo:

Eastern forktail new female b

This is not an orange bluet, but a newly emerged female eastern forktail. Note the absence of the orange at the abdomen tip plus the expanded orange area at the base of the abdomen.

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