A Pettable Blue-Winged Wasp's Mating Frenzy on Princeton Campus

This post gives a demonstration of wasp petting, and describes a funny thing that happened while helping our younger daughter move into her college dorm.

There's a wasp that's both pretty and pretty harmless. It's named after its wings, which reflect blue in the sunlight, and is easily identified by the rusty orange abdomen with two yellow spots. Scolia dubia, as it's called in latin, is a frequent visitor to the boneset in our backyard garden, more methodical in its nectar drinking than many other wasps.

It's understandable that people are afraid of wasps, given the stings most of us have endured after accidentally stepping on a yellow jacket's nest out in the field. But not all wasps are social like a yellow jacket, or even have nests. A female blue-winged wasp (males cannot sting) has no nest to defend, but rather digs down to lay its egg on an underground grub, then leaves the egg to hatch, consume the conveniently paralyzed grub (usually a larva of the June bug or the Japanese beetle), and emerge on its own as an adult.

Here's an example of how docile these creatures are as they peacefully sip nectar.



This year's visits seemed less frequent than in previous years, leading me to wonder how the species is faring, given all the talk of pollinators being in trouble.

That question was answered in the most unexpected way. Helping our younger daughter move into a dorm for her first year at Princeton University, I noticed one of these blue-winged wasps on a flower near the entryway. Then, on the third or fourth trip in with stuff, I happened to look over at the lawn in the courtyard, and noticed that hundreds of the wasps--let's call it an even thousand--were roaming in zig-zaggy patterns just above the grass. It wasn't at all obvious what they were doing. They looked lost, each flying around and back and forth in its own orbit. Perhaps the grounds crew had blocked their nest, leaving them to search in vain for the entrance. One passerby joked that the wasps were a metaphor for incoming freshmen. Another suggested that the University should take action on what seemed like a threat to the students.

My sense was that any danger was more perceived than real. Having spent many hours this summer photographing the various pollinators visiting the backyard boneset, seeing how harmless are the various bees and wasps when preoccupied with other matters, I waded out into the fray to have a closer look. Were they in fact lost? Or hunting? Or mating? There was no sign of prey, and if they were mating, then why was there so little interaction?

The first clue came only after watching them for awhile. Every now and then, some 20 or 30 of the wasps would suddenly converge on one location in what appeared to be a mad scramble in the grass. It's not easy to photograph wasps zipping around your ankles, but I did manage this photo.

And also this video of one of the sudden convergences. If they were fighting, it appeared brief. If they were mating, it looked pretty clumsy.



Some internet research made it clear that the goal of this mass, planar mingling of wasps was to mate. Some websites state that the males and females do a figure eight-shaped mating dance. Others suggest that those cruising the grass are males waiting for a newly mature female to emerge from the ground. They then converge on the female and compete for a chance to mate. If one's heart can go out to a wasp, my heart went out to the hapless female who, having just emerged as an adult from its underground birthplace, must immediately deal with a frenzied crowd of males seeking to pass along their genes to the next generation. If that is true, though, the sheer numbers and intensity of the gathering suggest that a whole lot of hatching was going on that day, and might the males have also just emerged from the ground? The explanations weren't quite making sense.

I did manage to get up close and personal with one of the convergences, close enough for a voyeuristic view of a male and female taking a tumble amidst the grass blades, clearly mating, with another male up next to them, bending its abdomen and probing in vain. What was surprising was how quickly most males gave up on the project, quickly returning to their holding patterns above the grass.

Here's the online description that best fits what I saw, in a 2016 paper entitled "The Scramble Competition Mating System of Scolia dubia" 

Males of the wasp Scolia dubia search for emerging females by flying low over the ground in areas, such as lawns, that contain the immature scarab beetles upon which the grubs feed. When an adult female emerges and is discovered by a searching male, other males often join the discoverer, forming a frenzied ball of males around the female. When captured along with these males by an observer, a freshly emerged female continues to attract males even after she has mated, presumably because her scent continues to be detected by other males. Some males of S. dubia also search for mates in shrubs and trees encircling a lawn as shown by the sexual response of these males to a frozen but thawed female placed in a shrub or tree known to be visited by flying males. Male flight activity peaks around midday but then diminishes as the afternoon proceeds. 

It was in fact late morning, sunny, warm, and some of the wasps were flying about the branches of the evergreen tree in the middle of the field. But there are many lingering questions. Do these gatherings happen only once per year, or multiple times in the summer? Was this lawn special in some way, or does this happen all over town? And how did these rituals play out before lawn mowers were invented?

One thing is clear. These docile wasps do us a favor by preying on a notorious garden pest--the Japanese beetle. Maybe some September, walking home from the Dinky station, you'll cut through campus and some late-flowering thoroughworts will catch your eye. There, in the clouds of white flowers, blue-winged wasps will be busy living their quiet lives, minding their own business while doing good deeds, their solitary pursuit of nectar giving no clue as to the elaborate choreography that brings them into being.

Attracting Pollinators With Boneset and Thoroughwort

Many people sing the praises of mountain mint and goldenrod for attracting pollinators, but my two favorites are a duo that produce large disks of small white flowers for a long stretch in mid to late summer.

This has been a banner year for boneset and its more numerous but lesser known sidekick, late-flowering thoroughwort.

With a name that spreads like the pagoda-shaped stems that carry its flowers, late-flowering thoroughwort adorns the sides of roads and railroads this time of year. I've seen it cover a whole abandoned field in Montgomery,

and there's a lone specimen blooming at the end of the track at the Dinky station.

It could be called a successful weed, and sometimes it can look a little ragged, perhaps influenced by how much rain comes. But this year it was the most elegant plant in the garden, its loose clusters of flowers like delicate hands reaching out to pollinators.

Late-flowering thoroughwort (left in this photo at the Westminster parking lot raingardens I care for) blooms just as boneset (right) is fading, which this year made for a seamless handoff between the two. Though boneset is comparatively rare in the landscape, it will make seedlings to increase its numbers when planted in a garden.

The two species can easily be told apart by checking the leaves. Boneset has pairs of leaves that are "perfoliate", which is to say they fuse to wrap around the stem. Thus the latin name Eupatorium perfoliatum.

By contrast, the leaves of late-flowering thoroughwort have petioles that extend the leaf away from the stem. The "serotinum" in its latin name, Eupatorium serotinum, means late summer. We could call it the serotinal thoroughwort, but we don't. In the common name, the word "wort" means plant, and if there's anything thorough about a thoroughwort, it's the copious blooms.

Both these wildflower species rise each year to the perfect height for viewing all the varied insect life they attract. Spend some time in that honey-scented space around the flowers and you'll discover an ecosystem in miniature, the flowers being a stage where the protagonists not only feed on nectar, but also look for mates, and sometimes put their lives on the line.

You might think it dangerous to be in proximity to the many kinds of bees and wasps that frequent this floral saloon, but I have never been stung in all my hours immersed in quiet observation.

I've even taken to petting the more docile creatures, like this "solitary" blue-winged wasp. Knowledge can cut through fear. It helps that the more aggressive insects, such as "social" wasps like yellow jackets, spend their summers elsewhere.

If anything, the pollinators are at much greater risk than I, with an occasional preying mantis showing up to snare a fly,

or a brilliantly disguised ambush bug lying in wait for a bumble bee.

Here's the ambush bug that was hiding in that previous photo.

Each plant has a time-release approach to flowering, with some clusters of flowers opening just as others are fading. Week after week in the summer, working in tandem, boneset and late-flowering thoroughwort continue to play host to a shifting cast of insect characters--each with its own traits, backstory and motivations--all the while adding ornament to the garden.

Synchronized Hazel Sawfly Larvae Pose for the Camera

This seems to be the summer for balletic poses by caterpillars and caterpillar wannabes. First came the dramatic pose of Datana contracta, happened upon in a patch of lowbush blueberries at Herrontown Woods.

Yesterday, fellow FOHW board member Sally Tazelaar sent a photo of another balletic display, this time seen on her husband Kurt's hazelnut tree in their backyard. The caterpillar-like creatures munch as a team, working from the edge of the leaf inward, and when disturbed, they pose as a team in surprising symmetry. Unlike humans who pose to be noticed, these larvae are more likely posing to hide. Maybe they are pretending to be dentations--part of the leaf--like the teeth in the uneaten leaf next to them. Doesn't fool us, but then again, we aren't the predators they are hiding from.

Some internet research suggests they are not caterpillars but instead the larvae of the hazel sawfly--Craesus septentrionalis for all the latin lovers out there. Hazelnut trees tend to be loners in Princeton's woodlands, the better to avoid being happened upon by hungry sawflies.

Thanks to Sally for the photo!

Oh Great! A Rice Weevil Infestation

They first appeared as specks on the floor when I was cleaning up the sunroom, which functions as a sort of mudroom where we store garden supplies, boots and charcoal. I had been cleaning out a plastic bin that held bags of long neglected birdseed and potting soil, plus whatever shoes and other items that had gotten thrown on top. The bugs looked harmless enough--small, slow moving--but they were a strange shape. For a moment I entertained the possibility that we were hosting a newly imported species, potentially invasive, that somehow had found its way into our house. But that thought seemed far too dramatic. I shrugged, figured they'd go away, and moved on to other tasks. A week or two later, my daughter found one climbing on the kitchen wall. I squashed it and continued cooking.

Then, one evening, a few of them appeared on the surface of a pot of hot water that I'd just poured a box of pasta into. That was the wakeup call. The pasta got thrown out, and an internet search began. They had weevil-like snouts, which was just enough information for the internet to work its magic. A search for "weevil, kitchen" instantly provided the answer: rice weevils.

That precipitated a closer look at the bag of birdseed that had sat largely unused in the sunroom for many months. "Economy mix," it said on the label, clearly one of those false economies where you get lots of birdseed for the price, and they throw the rice weevils in as a bonus.

The weevils had had abundant time to lay their eggs in the seeds, which provide the nourishment the larva need until they are ready to emerge as adults through holes in the seed coating. The bag should have been labeled "Rice Weevil Feed."

It was unnerving to learn that the weevils can fly, which may explain how they got up to the cupboards, where they infiltrated various boxes and bags of food.

There our detailed instructions on the internet for dealing with a rice weevil infestation. In my case, the bag of birdseed was poured into a vat of water outside to kill the weevils, then added to the compost with the food from the kitchen, far from the house; the packaging was put in a plastic bag and put in the trash.

All in all, it was a good motivation to clean the cupboards after years of accumulation. Haven't seen the tiny weevils since, but for the time being, all food in paper packaging is being stored elsewhere in the house, away from the kitchen. We were never very good at keeping the birdfeeder filled. Better in our case to keep feeding the birds indirectly, through all the seeds generated by the wildflower garden.

Monarchs Bring Dance, Delight and Larger Meanings to a Backyard

These are the glory days for monarch watching, with the backyard packed with flowers--a veritable feast that we are grateful to provide.

Lovely as it is, the levitated landscape of pinks and yellows, reds and whites, gains a deeper meaning when a monarch arrives to animate the garden with its fanciful, danciful flight. Brilliance of color is matched by brilliance of movement, with glides and hairpin turns, sudden dips or dartings upward, gracing a garden's contours as if its flight were a form of affection. With an uncanny mix of power and whimsy, the monarch looks to know what it's looking for, as it approaches then darts away or doubles back, each minute of its flight a hundred instant decisions. What makes it land on one flower after approaching and rejecting so many others, seemingly the same, is a mystery.

This morning we saw four at once, two of which flew together, then collapsed upon the carport roof, there to mate for a minute while I ran to grab my camera. The one in front looks to be the female, with thicker veins and no little black spot on the wing.

This one here is a male, judging from the less prominent veins,

and those little black spots on either side of its abdomen.

The monarchs were especially drawn to the joe-pye-weed that with the summer's heat and rain have grown to ten feet high, like a mountain range of flowers.

Sometimes, when a monarch flew and flew around the garden, looking, looking, I thought it might be searching not for nectar but for a milkweed plant to lay its eggs on. Our swamp milkweed disappeared some years back, and this year my wife bought this kind, with orange and yellow flowers. Turns out to be tropical milkweed, native to Mexico but not here. It's pretty, easy for nurseries to grow, and rebounds quickly if ravenous monarch larva consume its leaves. It's also said to have some aspects, given the nature of its more tropical growth, that would make our northern native species of milkweed a better option,

like this butterflyweed that is flourishing in a neighbor's garden.

Most of Princeton's milkweed is common milkweed, which is less ornamental, spreads underground, and can be found in fields, along roadsides, and in this case growing at the nearby Princeton High School ecolab wetland. Other species include purple milkweed, a few of which grow at Herrontown Woods, and green milkweed, found years back in the meadows at Tusculum.

The dominant ideology of our day has deprived us of the satisfaction of contributing to something beyond ourselves. I grow more garden and less lawn because I love native plants, but the monarchs connect the garden to something much larger. Each March, starting out from their wintering home on just a few acres in the mountain forests of Mexico, the monarchs stretch themselves across all of eastern North America, ambassadors of beauty, as if to tell us that all our small efforts, spread across the land, are additive in and to nature, that we can contribute to something profound. May the monarch teach us how to find that satisfaction in other aspects of our lives as well.

Monarch Butterfly Populations Down

Last year, monarch butterflies numbers were up in the Princeton area compared to previous years, but those heartening visits in our gardens and along roadsides did not translate into increased numbers at their overwintering grounds in Mexico.

The announcement of an official count was delayed this year for some reason. Numbers for the western population of monarchs, overwintering in pine and eucalyptus groves in southern California, came out a month earlier, in early February, and were down considerably. Finally, early this month, the announcement came that numbers of eastern monarchs have declined again. They've been lower the past two years, after small increases the two years prior, with 2014 having marked an all-time low. Over the past several decades, the overall trend has been down, with overwintering monarchs filling 44 acres of forest in Mexico in 1997, and only 6 acres this year.

So many factors affect the survival of monarchs. Illegal logging, windstorms, and coldsnaps can affect their overwintering success. This past fall's migration was affected by the series of tropical storms and the unusually warm weather that delayed the monarchs' flight south. Increased use of herbicides for farming genetically engineered crops has decimated the milkweed that monarchs need to reproduce. And then there's the looming hammer of climate change, as political and economic forces keep us trapped in dependency on fossil fuels. We see, in car commercials, town streets and new developments an ever expanding arsenal of exhaust pipes and chimneys aimed at the heart of nature.

There's some good news to mention. Gendarmes (armed police) have reportedly greatly reduced illegal logging in the monarchs' overwintering forests this past year. And people are showing an interest in planting and caring for milkweed. The stunning thing, which for the most part settles in the back of our minds, unthinkable but inextricable, is that the future remains optional.

While the world continues on its path of self-destruction, we can still find pleasure and joy in working with nature, and wonder why so much of humanity just "doesn't get it." This year, I'll be helping create a large native wildflower garden near the parking lot at Herrontown Woods. Except for a few spots like Tusculum, Princeton's open space is mostly forested, and so offers few flowers in summer and fall to sustain pollinating insects like the monarch. But the combination of windfall from storms and the clearing of invasive woody plants has created a clearing at Herrontown Woods that we can now plant. The aim is to replicate my backyard native garden in a publicly accessible space and on a larger scale, with signage so that people can become acquainted with Princeton's native flora. Much of my backyard garden is in turn modeled on the native flora to be found along the canal next to Princeton's Carnegie Lake. Anyone interested in helping the Friends of Herrontown Woods with this project can contact me through this website.

There's also a citizens' science initiative at this link, where you can provide data on monarch sites to a national survey.

A Spider Seeks To Catch the Sun

One evening, when the sun was dipping low, an ambitious spider thought to itself, "What if my web could catch the sun, and I could live upon its energy for all my days?

It tried from top and tried from bottom, but the slippery sun slipped, slipped, down and away.

Another spider, across the windswept bridge, saw the moon and thought, "What if I could catch the moon in my web, and feast upon its dreams? What a beautiful life it would be."

It tried from top and tried from bottom, and thought for a moment to have captured a lifetime of wondrous moonlight. But the moon climbed higher, higher and away.

Even the moon's reflection stayed stuck upon the glassy water.

Then another spider, having to cast its net like an airborne fisherman, looking down as the lake looked back, said to all the others, "Let us leave the sun and moon to their risings and fallings, and catch instead the bugs, who catch their energy from the plants, who catch the sunlight from the sun, and we shall feast upon the sun's energy for all our days."

And so it came to be, that the spiders lived in their village stretched across the water, catching bugs and summer sunsets, and moonlit dreams, while cars sped by, seeing nothing.

Afterthought: I didn't think about it at the time, but photographing the sun, even when close to the horizon, may not be the best idea. Even if I was only looking at the sun's image in the iPhone, not the sun itself, that's some pretty intense light. Keeping my eyes flitting about, not resting the gaze, surely helped. Lots on the web about this, due to the recent eclipse. Apparently the sun isn't bad for the iPhone, especially at sunset, but I wonder about the intensity of the image on the screen, and articles especially warn against using selfie mode with the sun because of the reflection of radiation off the iPhone onto one's eyes. Fortunately, I kept the camera pointed at nature rather than self, and it seems like no damage was done.

Wanted: A Few Good Herbivores

If you encounter a book or article that claims that, surprise!, invasive species aren't such a big problem after all (a few were written over the past decade), you'll probably find no mention of herbivory. They'll say that invasive plants are being falsely maligned, because actually they do wonderful things, like provide berries and nectar for wildlife. But it's to the plant's advantage to have its flowers visited and its berries consumed. What the plant doesn't "want" is to be eaten, and therein lies the problem with plants that become invasive. For whatever reason, be it an invasive's chemical defenses or ingrained dietary habits, the wildlife tend not to eat them.

Nature depends on consumption to keep things in balance. We love nature for its beauty and variety, but behind the scenes there's a whole lot of mastication going on. Take away predators and the deer population explodes. Introduce a new plant that the wildlife won't eat, and there's potential for that species to make habitat less and less edible as it displaces the natives. To fill this void in consumption, people have had to play the role of herbivores. What we do at Herrontown Woods, as we cut down dense groves of winged euonymus and other nonnative invasive shrubs, is to play the role of the missing herbivores, using our loppers for teeth.

There's some pleasure in the work--pleasing vistas created, serendipitous discoveries. But all things being equal, it would really be nice if the resident wildlife could show some flexibility in food preferences and fill the void in consumption. Invasives, after all, represent a huge, untapped food source for any animal willing and able to broaden its palette.

Given how much work it would be for humans to play the role of herbivores in the forest, any evidence of wildlife gaining an appetite for invasive plants stirs some hopefulness.

For instance, an invasive honeysuckle shrub was recently found stripped of its leaves. A closer look revealed something had been hard at work, its mandibles outshining our loppers: the caterpillar of a snowberry clearwing moth, also known as the "hummingbird moth" or "flying lobster", for its capacity to hover in front of flowers as it sips their nectar. Maybe if we had more summer wildflowers for the adult moths to feed from, their caterpillars would help control the populations of bush honeysuckle in Princeton's preserves. Nice to think, anyway.

And what's this orange plant growing on a dense expanse of invasive mugwort that grows as a monoculture along the gas pipeline right of way in Herrontown Woods? Dodder is a parasitic plant with little capacity to gather energy from the sun. Instead, it wraps itself around other plants and sucks out their juices.

Usually, its impact is small, but this must have been a particularly good year, because a sizeable patch of mugwort was sucked dry.

If only we could get the dodder (genus Cuscate) to preferentially neutralize the mugwort all along the right of way, some diversity might return. Again, a nice thought and tall order.

A new invasive trying to gain a foothold in Princeton is mile-a-minute vine, with a distinctive triangular leaf, a prickly stem, and a growth habit to match its name. Another post shows how invasive this annual vine can be , on farms just outside of town. Fortunately, after weeding out a small population back in 2007, I know of only two patches currently growing in Princeton, still small enough to control and hopefully eliminate altogether.

One's at the Princeton Battlefield. This year's growth was pulled out in early summer, and when checked in late August, the patch had only managed to produce a few leaves, all of which were being very effectively munched on by a weevil intentionally introduced to the U.S. to bring this rampant new species under control.

Ah, I concluded, to control mile-a-minute vine, simply reduce the patch in early summer, leaving enough for the weevils to sustain their population on. Their appetites appeared to be sufficient to prevent any flowering or fruiting that could lead to the patch spreading elsewhere.

Nice concept, but it wasn't working at the other site, down along the driveway into Rogers Refuge, where the vine had sprung back up, flowered and fruited, undeterred by the minor nibblings of the weevil. That patch had to again be pulled out by hand.

Another discovery was the work of the Ailanthus webworm moth, which had completely defoliated a young tree of heaven near the parking lot of Herrontown Woods. The moth, like the tree, is an introduced species.

If you have flowers like boneset growing in your backyard, you may be helping the adult moths to prosper.

Here again, though, the larvae have thus far been seen only on very young trees, with larger ones largely left untouched.

These are glimmers of hope, sprinkled across Princeton. It will take some concerted mastication by as yet unnamed herbivores to stem the tide of rapidly spreading species like porcelainberry, callery pear and stiltgrass--a giant uneaten salad that grows by the year. A little salt and pepper, perhaps?

The Viburnum Leaf Beetle's Gathering Harm

This fall, before the leaves fall off, check any Viburnum shrubs you know and love, whether in your yard or in your favorite nature preserve. Do the leaves look like this, pitted with holes, or even stripped down to the veins?

Most people have heard by now about the Emerald Ash Borer's rapidly multiplying demolition of our ash trees. Lest that devastation not be enough ecological and horticultural tragedy to absorb, there is another invasion underway in Princeton, by the Viburnum leaf beetle. This one--a European insect that first showed up in Canada before spreading to the U.S., is going after our understory, one Viburnum species at a time.

This and the above photo are of Viburnum dentatum, the arrowwood Viburnum, which grows here and there in our woodlands, preferring wetter soils. The light damage could have been done by a native insect, or by the first few Viburnum leaf beetles to show up, suggesting much greater damage the next year. Listed as "highly susceptible" on Cornell's website, the arrowwood Viburnum will be the first to succumb.

The maple leafed viburnum, frequently encountered along the Princeton ridge, is less susceptible and thus isn't showing any damage this year. As the Viburnum leaf beetle increases in numbers and exhausts the most susceptible species through complete defoliation, it will presumably begin attacking those that are less susceptible.

We are not completely helpless as yet another careless introduction to the continent wreaks slow motion havoc. This site offers some ways to prevent the beetles and their larvae from consuming your favorite specimens. As with all environmental damage done, the ecological and aesthetic services these shrubs were providing for free will now start coming with a price tag for human maintenance.

The Cornell site offers another ray of hope. An extension official in Rochester, NY asserts that even highly susceptible species may in the long term become viable again, as predatory insects and soil nematodes build up to prey on the Viburnum leaf beetles. Then, perhaps, the introduced species would come into some sort of ecological balance, doing some damage but not enough to kill the Viburnums.

It's a perfectly logical and reassuring scenario, and yet observation often brings into question the speed and effectiveness of nature's capacity to restore balance and sustain diversity. More often, invasive species remain dominant and destructive, be they Phragmitis, or Japanese stiltgrass, or porcelainberry. I called up the Frick Park Environmental Center in Pittsburgh, where I had first witnessed the devastating impact of Viburnum leaf beetle a decade ago. Asked whether they had seen any signs of balance being restored, they answered, "Not yet."

Related links:

The Pennsylvania extension service also has some useful information.

Past NatureNotes posts about the Viburnum leaf beetle, dating back to 2013, can be found here.

This post explores the likely aftermath of the Emerald Ash Borer invasion currently underway.