May Phenology 2: Insect First Appearances

by Carl Strang

Today’s seasonal comparison is between first appearance dates of insects at Mayslake Forest Preserve, through May. This includes April data, as there were not enough species in that month to consider alone.  As was the case with plants, the most dramatic difference was between this year and last: 15 species appeared a median 33 days later in 2013 than in 2012.

The differences from other years were smaller: 10 days later in 2013 than 2011 (15 species), likewise 10 days later than 2010 (13 species), and 5 days later than 2009 (12 species).

The bee fly Bombylius major first appeared 10 days later in 2013 than in 2010.

The bee fly Bombylius major first appeared 10 days later in 2013 than in 2010.

Green darners are our earliest dragonflies each year. In 2013 the first showed up 5 days later than in 2009.

Green darners are our earliest dragonflies each year. In 2013 the first showed up 5 days later than in 2009.

The numbers did not fully parallel those for flowering dates, in part because the months were combined, and in part because the sample sizes were smaller. Nevertheless, the 2013-2012 comparison is the consistent one. Also, this year is confirmed as the latest of the five I have been at Mayslake.


by Carl Strang

By my own subjective criteria, I have to declare that spring finally arrived, with a whimper, on April 16. I wasn’t at Mayslake Forest Preserve that day to see it, but the next day was a cold one, and it was clear that a few trout lilies and spring beauties had bloomed but then closed up in the lowered temperature. The weather stayed cold then, and so it wasn’t until Monday of this week that spring was manifestly present. One of its heralds was a patch of white trout lilies.

A representative bloom.

A representative bloom.

Spring beauties were scattered in little patches across the savanna.

Pink guidelines point the way to the flower’s center.

Pink guidelines point the way to the flower’s center.

A bonus was a colony of bloodroots.

They formed a circle reminiscent of a fairy ring.

They formed a circle reminiscent of a fairy ring.

That warm day also brought the first green darner dragonfly, and mourning cloak and cabbage white butterflies. We haven’t seen the last of the cool weather, but winter appears to be done.

Insect First Appearances

by Carl Strang

Yesterday I detailed the phenology of first flowering dates at Mayslake Forest Preserve. Today I want to share some equally impressive first appearances of insect species there. Most of these observations were made in the warm period in mid-March.

Before this year I never had seen a common green darner earlier than April 2, anywhere in DuPage County. This year the first migrants showed up on March 19, and tandem pairs already were laying eggs in the stream corridor marsh.

One question in the back of my mind relates to the relatively mild but snow-free winter we experienced. Some species may have benefited from the warmer winter, but others may have been set back by the lack of insulating snow. One species that may have benefited is the spring azure. I have never seen so many of those little blue butterflies as I have counted already this year.

This year’s first sighting of a spring azure came 54 days earlier than last year, 23 days earlier than in 2010, and 21 days earlier than in 2009.

So, here are the statistics. Species counts are smaller than for the plants that bloomed in March, at 5-6 species per year. First appearances ranged 16 to 80 days earlier in 2012 than in 2011, with a median of 30.5 days earlier. The range for 2012 vs. 2010 was 17 to 36 days earlier, median 23 days earlier. The range for 2012 vs. 2009 was 21 to 40 days earlier, median 28 days earlier. These medians were similar to those for first flower dates, despite the smaller numbers of species.

Tomorrow I’ll conclude March’s remarkable phenology with migrant bird arrival dates.

Mayslake Update

by Carl Strang

Life goes on at Mayslake Forest Preserve. Though there haven’t been any major stories to share lately, there are enough small ones to assemble into an update. We are reaching the end of the active insect season, but there still are a few straggling migrants coming through like this male green darner.

Normally shy, he was slowed by cooler temperatures, allowing a close approach.

I thought I’d added the last new plant species to my preserve list for the year, but then I ran into some smooth blue asters.

A small group of them is growing in a corner of the preserve where several other plant species have their only representatives, presumably from a past seeding.

Elsewhere I thought I found another new aster species, but apparently it was just an odd individual.

It keyed to panicled aster, but the leaves are narrower than most plants of that species at Mayslake.

Up at the friary site, large areas are greening with new growth.

The grasses look like recently seeded lawn grasses. I’ll be interested in learning what they are.

I continue to get out onto the preserve regularly, and will continue to share what strikes me as newsworthy.

OK, It’s Spring

by Carl Strang

How do you decide when spring has arrived? We like to impose concepts like seasons on the changes of the year, and our moods often are influenced by the weather. Atmospheric inertia and weather’s changeability deny our official seasonal transitions at solstices and equinoxes. Winter seems to go on so long in the Chicago area that in my own scheme I give it half of our seasons: early winter, mid-winter and late winter to go along with spring, summer and fall. In such a framework, the transition from late winter to spring is an important one, perhaps the most important of the year.

Certainly we have seen plenty of signs of spring. There have been some warm days. Ice is gone from lakes and ponds. Many species of migrant birds have arrived or passed through. Silver maples have finished flowering. I didn’t feel that spring had arrived, however, despite all of those events, until Wednesday. I saw the first green darner dragonfly of the season.

Here is a pair of green darners. The male is the one with green and blue colors.

How can I deny an insect that has flown up from the South to begin its northern breeding season? I don’t know if I want to make this one event my only determinant of this seasonal change every year. But sometimes it’s enough.

So, how do You decide when spring has arrived?

Mayslake Update

by Carl Strang

Today I want to share some miscellaneous notes on what has been happening at Mayslake Forest Preserve. Most of these are reflective of the season. For instance, thousands of migrating dragonflies have been passing through in recent weeks. Most of these have been green darners, with some black saddlebags and wandering gliders. I also saw the preserve’s first swamp darners (but was frustrated in my attempt to photograph them as they patrolled the stream). Some of the green darners paused to mate and lay eggs.

Birds also have been migrating. A good mix of warblers and others, including this scarlet tanager, have been refueling on Mayslake’s insects and berries.

Some insects appear late in the season. An example is this adult locust borer, the preserve’s first record of the species.

Of course, our year-round residents continued their activities, with signs of preparation for winter. For example, I have been seeing more skunk tracks than usual, in one case accompanied by scats.

The season’s progress makes this a time of daily change, and time spent outdoors inevitably brings its rewards.

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.

Late Season Insects at Mayslake

by Carl Strang

A couple days ago I put a finish on the floral season at Mayslake Forest Preserve. Today I’ll shake a few late insect photos out of the camera. We’ll start with some Odonata.

Green darner b

At Mayslake as elsewhere, hundreds of common green darners paused in their migration to hunt above the prairies and meadows. Migrating south is thought to be worthwhile for them and other large, strong dragonflies as they can extend their breeding season and spread their genes over a larger area. The various saddlebags species also migrate. Here is a UFO shot of a Carolina saddlebags that graced the mansion lawn area one day.

Carolina saddlebags 2b

A darner that shows up in a lot of places late in the summer is the shadow darner.

Shadow darner 3b

That vertical perching posture is typical. Common milkweeds have been hosting a late-season caterpillar, the milkweed tussock caterpillar.

Milkweed tussock moth caterpillar b

They are larvae of a tiger moth. I’ll close with a predator. This Chinese mantis assumed a cheerleading pose.

Chinese mantis 1b

Then, it began to groom its hunting apparatus.

Chinese mantis 2b

Earlier I showed an egg mass, which is how the species overwinters. Soon all the insects will be going into their various dormant forms to survive the long, cold, dry months of winter.

First Dragonfly

by Carl Strang


Each year the first dragonfly species to appear in northeast Illinois is the common green darner. I saw my first ones this year at Mayslake Forest Preserve on a warm, sunny April 17 (this photo of a female I took in 2002).




Males have blue abdomens. The bull’s eye pattern in front of the eyes is distinctive for this large dragonfly. Green darners we see in April are thought to have flown up from the south rather than to have emerged locally. This is a migratory species, though the ones that return probably are different from those that flew south in the fall. The leading current hypothesis is that migratory species like the green darner extend their breeding season and spread their genes over a wider geographic area. This makes sense of the fact that green darner nymphs also spend the winters in our ponds, and it appears that there easily could be a self sustaining local population. These early spring arrivals are getting a head start on the locals, which could include their own siblings, left by their parents before heading south.


So, this sighting does not allow me to list the common green darner as a breeding species at Mayslake Forest Preserve, but I will be surprised if it does not prove to have that status.


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