Oak Hedgehog Gall: Food and Shelter for Wasp Larvae

More than in past years, I have recently been paying attention to the insect galls that are found on oak leaves in Eliza Howell Park.

There are many kinds, but I have been focusing particularly on one called Hedgehog Gall, found on the midrib (middle leaf vein) of oak leaves.

Oak species are divided into two major groups: red oaks and white oaks. The tiny wasp responsible for the hedgehog gall, known as the “hedgehog gall wasp,” has a distinct preference for white oaks. The gall is much better known than the wasp.

This is on a Chinkapin Oak, one type of white oak.

As leaves are developing in the spring, the wasp lays eggs and stimulates the tree to abnormal growth at the egg site. The gall is a growth produced by the plant, not the wasp, but it provides the seasonal home and the nutrients for the wasp larvae to feed and grow. Each hedgehog gall has a few cells for developing larvae.

Though the galls are often round, they get their name from the shape that is thought to resemble a hedgehog.

These galls can be found on either the top or underside of white oak leaves and have orangish or reddish hairs. They might look soft, but are very firm, providing excellent protection for the wasp larvae.

If I have my identification correct, these are all hedgehog galls.

Since I started looking carefully, I have been finding many other types of galls on oak leaves. The ones represented in this collage are mostly on red oak trees.

An oak leaf gall is an amazing phenomenon. The insect induces the tree to build a “nest” to raise its young. And, as galls rarely do the tree any real harm, the cost to the tree is minimal. Another of Mother Nature’s many ways of living together.

Virginia Creeper: Fall Color Season Begins

“Leaves of three, let it be. Leaves of five, let it thrive.” The first line of this rhyme, referring to Poison Ivy, is better known than the second. The second vine is Virginia Creeper, similar to Poison ivy in some ways, but with five leaflets instead of three — and much more welcome.

Late in September, Virginia Creeper is one of the most stunning plants in Eliza Howell Park.

Virginia Creeper is both a creeper and climber. It clings to trunks and drapes itself over dead and living branches, turning red or burgandy in contrast to the often green or yellow of surrounding plants.

Though an aggressive grower capable of climbing large trees, Virginia Creeper is not considered a threat to the health and vitality of the natural environment. It is native to our area, a vine with which other native plants have long been compatible. (This map of its native range is taken from Ontario Wildflowers.)

Attractive as the leaves are in early Fall, for some viewers the appearance of the fruit is even more striking, dark blue berries on red stems.

While the berries are usually described as toxic to hunans, they do not last long after they ripen, eagerly eaten by both mammals and birds. Some 30 species of songbirds have been confirmed as comsuming them, Norther Flicker being one.

(Photo courtesy of Margaret Weber.)

Fall leaf season is now starting in Eliza Howell. Virginia Creeper is contibuting to an excellent beginning.

New England Aster: The End of Summer

Since April 23, I have written about different wildflowers of Eliza Howell Park 10 times. The flowers have been irresistible this year and I have been excited to learn that the park has even more species than I had thought.

As summer ends, the flowers are fading fast. One more species should be featured, however, before the flower season is totally over: New England Aster.

I have long thought that the signature flower of September in Eliza Howell is Goldenrod. And it is dominant this month. But the bright purple aster is an additional highlight and the two go together extremely well.

New England Aster is a late season bloomer, found in open fields and at the edges of forest. It is native to much of North America.

Most of the asters in Eliza Howell grow to about 4 feet high, scattered in the wildflower prairie in the park, not forming large patches. They repeatedly invite me to get closer to admire both individual blooms and clusters.

I feature New England Aster as my last flower post of 2020 not because it is rare or unusual, but because it announces the end of sunmer. September is truly a month of transition for flowering plants in Southeast Michigan: at the beginning of the month many of the summer flowers continue to thrive; at the end of September there are very few that have not faded.

New England Aster is perhaps the brightest of the fall wildflowers.

Four months ago the alpha of this year’s featured flowers was the delicate Spring Beauty. I think New England Aster is a deserving onega.

Bald-faced Hornets: Locating the Nests

One of the greatest benefits of taking many nature walks in the same location year after year is a growing ability to identify patterns, to learn the WHEN and the WHERE of nature’s annual cycle.

Near the beginning of September, I expect to see the first of the 8 or more Bald-faced Hornet nests that I find every year in Eliza Howell Park

This year it was September 3.

Bald-faced Hornets are a type of social wasp (“social” here means living in a colony that has a queen and workers). They are fairly large and are an attractive black and white.

The construction of the nest was begun much earlier in the season by the queeen, the only one to survive the winter, but I do not see the nests until they are full size. The large nest (roughly basketball size, but shaped more like a football) hangs among tree leaves, usually well enough hidden (until the leves fall) that it is difficult to find despite the size.

In September, the entrance way, located near the bottom, is busy with traffic, as can be seen in this photo taken by Kevin Murphy.

Based on observations from previous years, I have had a good idea about WHEN to find the nests. But identifying the WHERE has been more difficult. They are constructed in a variety of deciduous trees in different locations in the park.

The last couple of years, though, I did notice one or two each year in the maple trees along the the entrance drive from Fenkell.

So this year, when it was time, I made a point of checking these trees very carefully.

During the first week in September, I found, in addition to the one pictured at the beginning of this post, the 4 others that are in this collage. All 5 are in these maple, from about 8 to 15 feet from the ground.

I will no doubt find this year’s other nests scattered around over many acres, but I have now identified some sort of a pattern regarding location. Next year my search will likely start here again and will include other similar maple trees

Butterflies on Purple Coneflowers: A Photo Report

This has been a great summer for butterflies in Detroit’s Eliza Howell Park.

Since nectaring butterflies frequent Purple Coneflowers, for about three weeks starting on July 20 this summer, my butterfly watching regularly included a stop at a coneflower clump or two. With the flowers at the top of the plants, some three feet high, the coneflowers provide an excellent opportunity for picture taking.

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20200731_124928Monarch (July 23)

20200724_142352Giant Swallowtail  (July 24)

Resized_20200727_125009Painted Lady (July 27)

20200731_112938Eastern Tiger Swallowtail (July 28)

Resized_20200831_213504Viceroy (July 31)

20200831_213614Black Swallowtail (July 31)

Resized_20200831_213921Red Admiral (August 5)

20200807_141039Clouded Sulphur (August 7)

20200831_214325Pearl Crescent  (August 8)

The coneflowers have now gone to seed. But they will bloom again next July and  the butterflies will be back. I am also planning to be there.

Bur Oak: Singing Its Praises

Among the many different species of oak trees found in Eliza Howell Park, Bur Oak is one that, in my mind, merits special recognition.

My attention starts with the acorns. Ever since I was young, I have been fascinated by these large nuts, reportedly the largest of any North American oak, almostly entirely covered by a mossy cap.

I cannot resist taking pictures, even when the acorns are not yet mature.

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In bumper crop years — and this year appears to be one — these acorns are so noticeable that the tree looks a lot like a fruit tree.

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The leaves are also easily recognizable, large and wider near the end. This, too, I learned early and is one of the reasons I have always been able to identify this species in the midst of many other oaks.

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Bur Oak lives life leisurely, growing slowly and living a long, long time. And as it survives decade after decade after decade, it can get to be massive.

I have more than once measured one particular Eliza Howell specimen.

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At four and a half feet from the ground  the trunk has a circumference of well over 15 feet, which translates to a diameter of nearly 5 feet, perhaps the biggest tree in the park.

Using the standard method of estimating tree age based on diameter (and taking species growth rate into account), this individual is estimated to be nearly 300 years old.

In 1720, Detroit’s population was about 200 people.

Given how long these oaks have been growing, one can expect that Bur Oak is  native to this part of the country.

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As this map suggests, Bur Oak is more of a prairie tree than it is a forest tree. It has been one of the key oak species in “oak openings” or “oak savannas.” 

Grasslands have historically burned with some regularity. Bur Oak’s bark is fit for this environment, thick enough to make it fire resistent.

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There is a great variety of oaks — and acorns — in Eliza Howell and I am slowly getting to know many of them.

But I confess a stronger attraction to one of them than to (most of) the others. I am a Bur Oak fan.

Butterflies Battered and Torn

I enjoy taking pictures of butterflies and am excited when I come upon a “perfect” specimen. Butterflies, however, do not have an easy life and it is not unusual to see ones with damaged or torn wings.

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I recently found this Tiger Swallowtail as it was nectaring on Ironweed, probably the tallest wildflower in Eliza Howell Park. The setting was lovely and it is easy to think that the picture would have been better if the wings were not damaged, but danaged wings are also part of the reality of the natural world.

Here is another example of a Tiger Swallowtail carrying on despite missing a sizable chunk of its wing.

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What happened? There is no way of knowing, of course, but missing parts on butterflies might be the result of an attack by a predator.

Most bird species eat insects in the summer and they are the most common predators of butterflies. Missing parts of butterfly wings could very well mean that a bird just missed.

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This Viceroy looks like it barely survived whatever it experienced. But it too is carrying on.

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Earlier this summer, I was making a  photo collection of all the different butterflies that visit Purple Coneflowers and was pleased when I was able to add this Red Admiral. Note the wing damage.

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This is one of the very few Baltimore Checkerspots I see in Eliza Howell. It has wing damage and the colors are faded, but, especially because I don’t see them very often, I was very pleased to be able get a picture.

On addition to birds, other butterfly predators include insects such as dragonflies and praying mantises as well as spiders.

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This is the only picture I have in 2020 of a Great Spangled Frittilary, another butterfly that I see only occasionally.

In addition to being directly preyed upon, butterflies might suffer torn wings when snagged by plants or when they are freeing themselves from spider webs.

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Earlier this month, I took my first-ever pictures of a Tawny Emperor. It too had part of its wing missing.

I like butterflies, in part, for their beauty, a beauty enhanced by an undamaged body. As a student of nature, I am also interested in learning about the threats and challenges these butterflies face and how they continue to function despite being battered and torn.

Praying Mantis Watching: An Opportunity

As Praying Mantis season begins in Eliza Howell Park, I am pleased to announce that we are cooperating with  Detroit Audubon to provide an opportunity for those interested to watch — and perhaps to photograph — these fascinating insects.

DETAILS ON PARTICIPATING IN THE ELIZA HOWELL MANTIS WATCH CAN BE FOUND AT THE END OF THIS POST.

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The Praying Mantises are now reaching maturity and Kevin Murphy (my fellow mantis enthusiast) and I have been noting their increased visibility in and near their favorite wildflowers. They seem to be especially attracted to some of the goldenrods.

It can be a challenge, at times, simply to spot them, as they perch unmoving on plant stems.

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They can be so well camouflaged that even the best searchers miss many, maybe most. They are variously colored in shades of green and brown, and I find those almost fully green the most difficult to find when the leaves are still green.

The second of the following pictures is enlarged to show the mantis that looks like one of the goldenrod leaves from only a few feet away. The challenge is to find the mantis in the first picture

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Their stalking method —  avoiding most movement — has real advantages for our watching once they are found. There is a good chance that they will be in the same locations a little later if we return to point them out to someone else.

In addition, we can often get fairly close without scaring them away, allowing for some good views.

They don’t move much, until prey comes close. Then they snag the bee or other insect with their long grasping front legs. They eat on the spot, without killing the prey first.

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Praying Mantises have a limited lifetime once they reach adulthood. They will soon be mating, after which females lay eggs. It is not unusual for observers who visit the area frequently to see both of these events, each of which takes hours to complete.

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There are reports of females eating males after or during mating, starting by biting the head off. I have not seen this.

But I have often seen females laying eggs, first making the egg case into which she deposits the eggs. The case hardens and the eggs remain through the winter (when not eaten by some predator or otherwise destroyed) and energe from the case when the weather warms in the spring.

In Eliza Howell, they simetimes lay their eggs on goldenrods, but they often use the limbs of shrubs or small trees (something a little more sturdy than a flower) near their feeding and mating area.

Adults die shortly after mating and egg laying.

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We are hoping to schedule the field trip for the most active time, so we want to wait a bit longer before set the exact dates. But the indications are that it will likely be quite soon.

If you are interested, please let Detroit Audubon know* that you want to be on the list of those to be kept informed. As soon as we can, we will inform Audubon of the dates and hours when at least one of us will be available on site to assist you in locating the mantises when you arrive.

* To be on the email list, send a message to

programs@detroitaudubon.org

with “STOP field trips” in the subject line.

There are many marvelous seasons in the park. Praying Mantis season is definitely one.

Mid-August in Eliza Howell Park: Signs of Seasonal Change

For the last several weeks, much of my attention during nature walks in Eliza Howell Park has been on the summer meadow wildflowers and the insects they attract.

This week that began to change, as I became more aware of the fact that the summer is moving toward a close.

These images, from my most recent walks, remind me that the transition to Fall is, without a doubt, happening now.

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The Virginia Creeper leaves are beginning to turn and the berries have reached their full size. Before long, I will be admiring the lovely blue-colored ripe berries on red stems.

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I think of Goldenrod as the distinctive flower of September, though these are aleady blooming. Most of the Goldenrod varieties found in Eliza Howell are only a couple weeks behind these, budding to flower soon.

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The wild Black Cherry trees are filled with fruit that is red on the way to  black. Dozens of birds, especially Cedar Waxwings and American Robins, are feasting on this year’s bumper crop.

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The seedpods are forming on Common Milkweed plants. Though it will be some time yet before the pods mature and open to let the seeds be scattered in the wind, the process is well on its way.

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In late summer, a few scattered webs of the Fall Webworm Moth can be found on the ends of tree branches. The caterpillars spin the web to protect themselves as they eat leaves. As the “Fall” name suggests, these webs are another sign of seasonal change.

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Within the thick foliage of Sugar Maple trees, the samaras — the winged nuts/seeds — are now evident. While some maples drop their seeds in the Spring, Sugar Maples are getting ready for their Fall dispersal.

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Checking some other trees to assess how the Fall nuts are progressing, I note varying but clearly advancing stages of developnent in (from top left clockwise) Walnut, Chestnut, Hickory, and Oak.

This is August, but there are many signs of September in my favorite park in Detroit.

 

Great Golden Digger Wasp: Irresistible and Safe

I don’t see them on every summer walk in Eliza Howell Park, but I always look twice when I do.

There is much to like. The Great Golden Digger Wasp is colorful, impressive in size, and not a stinging threat.

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Wasps are often described as “social” or “solitary.” Social wasps nests in colonies with a queen and the workers aggressively defend the nests. Yellowjackets and Bald-faced Hornets are examples of social wasps.

The Great Golden Digger Wasp is a solitary wasp. Females make their own nests individually (digging holes in the ground) and, once eggs are laid, do not defend the nests. Humans are not perceived as a threat.

The adults feed on nectar.

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Lately, a favorite nectaring flower has been Culver’s Root. Here they are easy to see and are near eye level. Knowing that they are not a threat to sting (unless I do something like grabbing one!), I try to get close ups, close enough to see the golden hair on the head.

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This wasp is not a stinging threat to humans, but the nesting female does sting other insects. I have not yet been able to observe their nesting behavior in Eliza Howell, but the following is the reported practice.

After digging a vertical hole in the ground, with several side cells, the female hunts a katydid or cricket or similar insect. She stings it, paralyzing it, transports it to the nest, and places one in each cell. On the body of each  living but paralyzed insect, she lays an egg, then seals the hole. After the egg hatches, the larva eats the stored food before going into a cocoon to spend the winter.

The new adults emerge in the late spring or early summer for an adult life that usually ends in August. The first one I noted this year was nectaring on a milkweed flower.

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There is only one generation a year. I have enjoyed getting many good looks this year. Perhaps next year I will have an opportunity to observe the nesting behavior the Great Golden Digger Wasp.