Insect First Appearances in April

by Carl Strang

In the previous post I shared data from Mayslake Forest Preserve showing that plants are continuing to bloom 2-4 weeks earlier than in the previous 3 years. Insects that made their first appearances in April likewise were ahead of 2009-2011.

The eastern forktail was representative, appearing 35 days earlier than in 2009, 41 days earlier than in 2010, and 34 days earlier than last year.

Sample sizes were small, though, with only 7 species to compare between each pair of years. The median difference between 2012 and 2009 was 43 days earlier (range 169 days earlier to 25 days later). The median was 41 days earlier than in 2010 (range 110 days earlier to 24 days later), and 35 days earlier than in 2011 (range 27 to 68 days earlier).

The first pearl crescent appeared on April 9 this year. That date was September 23 in 2009, July 2 in 2010 and May 12 last year.

These huge ranges may better be described as representing better survival for many species in the mild winter just past, so that there were more first-generation individuals, increasing the likelihood that I would see one. The pearl crescent could well be a case in point with respect to 2009 and 2010.


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.

Early Insects

by Carl Strang

This spring, plants have been flowering a couple weeks ahead of last year, and some of the insects are making early appearances as well. This spring azure butterfly was out by April 12 at Mayslake Forest Preserve.

The earliest dragonfly of the year always is the migratory common green darner, the first of which showed up on April 5. That’s one of my earliest observation dates for the species. Last week I found a few other odonates at the stream corridor marsh, including this pair of common spreadwings in wheel position.

There also were both eastern and fragile forktails, the latter a new preserve record. Another new insect for the Mayslake list was this skipper, which I believe is a Juvenal’s duskywing.

A colony of eastern tent caterpillars is well under way north of the off-leash dog area.

To the right of the nest you can see the egg mass from which the caterpillars emerged.

Though flowers are blooming earlier, pollinators have not been caught napping. Here a carpenter bee visits cut-leaved toothwort flowers.

At first I thought it might be a Bombus impatiens worker, but the queens of that bumblebee species still seem to be searching for nest sites. At most they are beginning to tend their first set of larvae. The lack of yellow on the relatively hairless abdomen of this individual rules out all bumblebees.

Finally, I can declare the singing insect season to be open. The first greenstriped grasshoppers were displaying at Mayslake on April 20. In my 5 years’ experience with singing insects this is the earliest crepitation I have heard from that species, by 8 days.

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.

Early Insects

by Carl Strang

Large insects are beginning to appear at Mayslake Forest Preserve. For some weeks I have been seeing mourning cloaks, which overwintered as adults.

Mourning Cloak b

The above photo I took at Fullersburg last year. Another butterfly that overwinters as an adult is the eastern comma. This one at Mayslake apparently had a close call, probably with a bird. Note the missing section from the left hind wing.

Eastern comma b

There have been some orange sulfurs, which overwintered in the pupal stage.

Orange sulfur b

Their close relatives the cabbage whites have been common all over the preserve. Earlier  I celebrated the arrival of the first common green darner dragonflies, migrants from the South. The first locally emerging dragonfly I saw was this male common whitetail at Mayslake last week.

Common whitetail immature male b

He is recognizable to species and gender by his wing pattern, but he has newly emerged and so still has the immature coloration on his abdomen. The first mature Mayslake damselflies were eastern forktails.

Eastern forktail male b

The above photo of a mature male is from a few years ago, I believe at Songbird Slough, but this is our most common and widely distributed damselfly.

I have not had good luck photographing bumblebee queens this spring. Bombus impatiens has been common, and I saw one Bombus fervidus near the friary on May 22, at the same honeysuckle bush that hosted two of these:

Carpenter bee 2b

This is the large carpenter bee Xylocopa virginica.

The first monarch butterfly arrived at Mayslake this week.

Monarch 2009 1b

This individual is too clean to have made the trip all the way to Mexico and back. It is an offspring of those that wintered down there, made part of the journey back north, and laid their eggs on milkweed plants they found in the southwestern U.S. I shake my head in amazement at the instincts that guide these insects, with their pinhead brains, through journeys last made by their great grandparents.

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