A Honey Bee Swarm, and a Specialist Native Bee on Spring Beauty

A couple interesting sightings of bees in Herrontown Woods recently. Working on trails on April 12, I paused and heard what sound like a buzzing coming from somewhere nearby. With so many machines of transport shut down due to the pandemic, it was quiet enough in the woods to hear what turned out to be a swarm of honey bees 40 feet up in a snag, still erect but completely stripped of branches. They were flying around a hole in the trunk. I went to get another load of stepping stones from our stockpile, but by the time I returned a half hour later, they were gone.

Some internet research led me to an entomologist at Cornell University, Scott McArt, who was kind enough to reply:

"From what you describe, it’s very likely a colony that swarmed. During swarming, half of the bees will leave the hive with their old queen, while the other half of the bees will stay in the hive with a new queen. The exiting bees will typically leave the hive and congregate on a nearby branch for a few minutes or hours, then move on to the next branch (or their new home, once they’ve found it). It’s an impressive sight when thousands of bees assemble onto the branches and/or move en masse to the next location, hence why it’s called a “swarm”." 

"Mid-April is a bit early for swarming, but not unheard of, especially since there’s been some warm weather and flowers popping up over the past few weeks. Aside from a bear getting into the hive, it’s really the only reason you’d see thousands of bees up in a tree right now. So if you didn’t see a bear, I’d say you saw a swarm :)"

Another bee sighting was much more subtle. Over the past month, the most numerous spring ephemeral wildflower has been the spring beauty. Again working on a trail, I happened one day to look down and see a tiny bee visiting one. I was crouching down to catch a photo when the bee dropped off the flower and stood motionless among the dead leaves--reminiscent of the freezing behavior rabbits use when approached. The same happened another day when I again sought a photo.

I was able to find mention of a Spring Beauty Bee (a miner bee named Andrena erigeniae) in a list of specalist bees.

An article in the Baltimore Sun entitled "Searching the Forest for the Bees" describes the bee's lifestyle, which includes only a brief appearance in the spring. It's useful to know that honey bees are not native to America.

"Unlike honey bees, which congregate in hives, most of the forest bees are loners that spend the bulk of their lives in the ground. They emerge for just a few weeks in early spring to pollinate flowering plants, shrubs and trees before the forest leafs out and shades the understory from the sun.

Many are "specialists," Droege said, focusing on a particular type of plant or flower.

For example, he said, there's a bee that specializes in collecting nectar and pollen from spring beauty, a ground-hugging pink or white wildflower that's one of the earliest harbingers of spring. One can't exist without the other, he said. In fact, many flowers have features that attract particular pollinators, while discouraging or excluding others.

"Flowers were all designed by bees," Droege said, over millennia of co-evolution."

 As a botanist, I had naturally assumed that all bees were designed by plants.

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.

Entomologist Rachael Winfree Offers Advice on Catering to Bees

Some time back, Rachael Winfree, an entomologist at Rutgers, generously agreed to meet with us at the pollinator garden we're creating at Herrontown Woods, to discuss ways it might better fill the needs of bees. For an hour, she poured out information while I scrambled to take notes. More can be found at her website, at the bottom of this post.

DEAD WOOD: Her first thought was that she liked all the wood strewn about, in the form of trees felled by wind and ice storms over the past ten years. The bodies of trees live a long life after death, providing a home for all sorts of insect life. Fallen trees are one of the places bumble bees make their nests underneath.

SOIL: She liked less the soil--mostly heavy clay. The many kinds of bees that build their nests underground prefer looser, more sandy soil. Perhaps we could bring some sand in to lighten up some areas, she suggested, or dig up the soil here and there to make the bee's job of digging easier.

SLOPING GROUND: Slopes would be good, too. Water runs off a slope better, so there's less chance that the bee's underground home will be flooded. Our pollinator garden has no hills, but it does have the hillocks made when a tree is uprooted. The rootball angles up into the air, leaving behind a hole in the ground with slopes on all sides. America, it is said, was very lumpy back before western settlement, as each tree over the millenia would eventually fall, its raised rootball leaving a depression.

XERCIS SOCIETY: She mentioned the Xercis Society and its website on multiple occasions. She's on its board, and thinks it's one of the best sources of ideas for creating habitat for insects.

WASPS VS BEES: Wasps visit flowers not to collect pollen but to sip enough nectar to get through the day. They are therefore poor pollinators, since they don't collect pollen and therefore are less likely to spread pollen from one flower to another. To reproduce, they prey on other insects, which they collect and use to nourish their young.

BEES ARE VEGETARIANS: Bees are essentially vegetarian wasps. They use the protein in pollen to feed their young, collecting a bunch of pollen and then laying an egg in it. Different bees carry pollen on different parts of their bodies. The classic honey bee, the cow of the bee world, not native but widespread in the service of agriculture, carries pollen on the back legs, as do bumblebees. One bee carries pollen on its belly, which is very cute to see when one turns the bee over.

SOCIAL VS SOLITARY BEES: Social bees, such as honey bees and bumble bees, are in the minority. Most types of bees are solitary. These types are very unlikely to sting, because stinging is a very dangerous activity for a bee, and a solitary bee is on its own. Bumble bees and other social bees are "on the wing" longer than solitary bees, meaning that they are around all summer rather than for just a couple weeks.

BEES IN DECLINE?: Though the news media has been reporting that bees are in decline, Rachael contends that there isn't all that much evidence to back that up. There are no long-standing studies of bee numbers to reference. Complicating any effort to tally bee numbers, there are only three taxonomists who can identify all 160 or so species of native bees in New Jersey. (I didn't catch the names, but two of them may be John Ascher and Jason Gibbs. When googling John Ascher, I came across this very useful looking manual: How to catch and identify bees and manage a collection) Bees, unlike plants, must be killed in order to be identified, and though some of that is necessary for research, it's not necessarily an activity entomologists want to promote. Bees may actually benefit from the habitat fragmentation that comes with suburban sprawl.

SPECIALIZED BEES: I had wondered if there are specialized bees that depend on a particular plant species that we could then plant to help that bee species. She mentioned two to get me started: a bee called Andrena erigeneae that feeds exclusively on spring beauty (Claytonia virginica), and the Rose-mallow Bee (Ptilothrix bombiformis), which has a black velvet appearance and feeds on Hibiscus. (I found this informative article that lists many others: https://vnps.org/specialist-bees-need-special-plants/)

SMALL CARPENTER BEE (Ceratina sp.): a common bee around here.

NESTING: Bumble bees nest under logs, or at the base of bunch grasses.

MOBILITY: Small bees fly only a couple hundred feet.

PLANTS TO ATTRACT BEES: sweet bergamot, lavender, mountain mint--especially Pycnanthemum tenuifolium

MORE INFO: Her website has useful pdfs, including a primer on New Jersey bees.

Early Autumn Vignettes

Nature can sometimes come in close in the fall. This wooly creature, the caterpillar of a great leopard moth, not to be confused with a wooly bear, showed up on the floor in a corner of our bathroom.

Perhaps it came in with some firewood stacked in the sunroom next to the bathroom. I meant to take the caterpillar outside, but got distracted, and found it the next day in the hallway beyond the family room. At that point, it was given transport out to the back corner of our yard, where it will presumably find some cover for the winter.

Bumble bees can get soporific in the fall, dozing on a flower as if they've forgotten their reason for being, which all but the queens may well have. This one landed on my hand while sitting outside a cafe on Nassau Street. Its curiosity seemed harmless enough.

Another surprise came while walking home on Moore Street. Pokeweed (inkberry) is a large, fleshy plant that often looks rank and weedy, but every now and then, it grows in a place that reveals an elegance and beauty. Its perennial root sends up a new stem each year, unlike its close relative in Argentina, the ombu, which has a tree-like perennial top but lacks a real tree's xylem.

A subtle surprise of the ornamental seed variety came during a recent walk at Herrontown Woods, where the path intersects with one of only three hearts a' bustin' shrubs (Euonymus americanus) as yet to be found growing wild in Princeton. These three somehow grew tall enough to elude the deer, whose appetite for the plant has kept all other specimens in the woods only a few inches tall.

Also coming as a recent surprise is the University's native prairie planting next to the Firestone Library. It's off to a good start, with the classic eastern grassland species.

This ambitious planting comes after another attempt at a native grassland a few years back, at the psychology building, was mowed down after mugwort, Canada thistle and other weeds were allowed to invade until they became unmanageable. It's good to see the University didn't give up on the concept. This latest planting next to Nassau Street is higher visibility, which could prioritize its maintenance. If there's someone on staff who can provide the early, skilled intervention to keep the weeds out of this complex plant community, it should become a low-maintenance planting whose rich diversity echoes the book collections stored below.

A Mexican milkweed growing next to our carport turned into a miniature monarch butterfly nursery this summer. The monarchs are unpredictable as to which milkweeds they'll actually lay eggs on, but this one plant finally played host to some caterpillars late in the season.

Even harder to predict, oftentimes, is where the fully grown caterpillars will go to make their crysalises,  but these were easy to find underneath the shingles of the house. This particular one did not mature into a butterfly,

but a few others did, the evidence being the wispy remains of the chyrsalises coinciding with sightings of a couple monarchs whose flight looked tentative in the way one would expect first flight to be. Reports on fall migration back to Mexico have been promising thus far, though the next post on Monarch Watch should speak to any impact from the hurricanes.

(Note: The Journey North site has more frequent updates, and for NJ, check out the Monarch Monitoring Project in Cape May )

Fall is also a time for biking down to university soccer games, in the process crossing the pedestrian bridge, where the native persimmon trees planted there have finally risen high enough

to push their fruits close against the wire mesh. Not quite ripe when this photo was taken, but there are two home games to go. Catching them when they're ripe would be a fine surprise.

What's With the Witch Hazel?

Previous years' posts about the witch hazel growing along Shapiro Walk on Princeton campus were from mid-March. These photos are from late February, when the blooms had likely already been out for a week.

These are not the native witch hazel, which blooms in late fall, but are most likely a cross between the Japanese and the Chinese species (Hamamelis japonica × H. mollis).

It's hard to fully rejoice in their blooms while walking by in a winter hunch.

A few flies showed up for the party, but there were no bees to be seen.

Coralberry: Late-Bloomer in the Whole Earth Center Raingarden

The narrow little raingarden in front of the Whole Earth Center, along the Nassau Street sidewalk, is a bit of an anomaly. It flourishes beyond all expectation and despite several factors that could easily work against it. Portions of it are covered by a canopy, which means those areas receive no rain. And though I weed it periodically, do some thinning and trimming, and clean up any trash that blows in, there are others who take care of it as well. A professional landscape crew comes in each spring and lays down fresh mulch. I see signs now and then that someone on staff is also paying it some attention. That none of us communicate or coordinate would normally lead to problems, and yet it all works out.

There are, too, a few plants in the raingarden that wouldn't normally be considered ornamental. Fringed sedge and deertongue grass are wild natives, and yet provide a look of surprisingly attractive grassy opulence along the sidewalk's edge. And the native coralberry in these photos, taken a few weeks ago, makes a nice mound at the building's corner.

Bees, I discovered one day walking by, take an interest in coralberry deep into the fall.

A closer look was rewarded by this scene. Turns out the coralberry has its own brand of commerce--a sort of roadside stand set up in front of the Whole Earth Center, serving organic nectar to honeybees.

It's not coincidental that this native shrub looks reminiscent of the nonnative and frequently invasive honeysuckle shrubs. Both are in the family Caprifoliaceae. Grab your botanical latin books to find out the meaning buried in the scientific name, Symphoricarpos orbiculatus.

At the other end of the raingarden are the more mainstream native shrubs, favored for the showy flowers and bright fall colors that the coralberry doesn't deliver on. Fothergilla (witch alder) turns brilliant orange, contrasting with the purplish oak-leaved hydrangia behind it.

One nice trait of the corralberry for us lazy propagators is that it makes new plants when its branches touch the ground. Each can be dug and grown into a fullsize shrub. From old raingardens, new ones can be born.

July Flowers

Purple coneflowers greet passing traffic on Harrison Street.

Backyard buttonbush thriving in the runoff from the neighbors' yards.

Some leaves on the buttonbush were fashioned into a webby tent for a clutch of baby spiders--by the spider, not by me.

Culvers root just beginning to open its long lines of flowers.

Towered over by a pokeweed (Phytolacca americana), which looks like it has aspirations to rival its tree-like relative in the pampas of South America called the Ombu (Phytolacca dioica). Flowers tba.

Clouds of tall meadow rue attract tiny bees.

A good year for elderberry, and just about everything else.

The Bees in Your Backyard--A talk by Olivia Carril

Interesting talk at the Princeton Public Library on bees, by Olivia Carril, co-author of a new book on North American bees called "The Bees in Your Backyard". Most engaging was her clear passion for the subject, which is expansive, given the 4000 species of bees in this part of the world. Each species has its own story, its own special approach to living a bee's life, and new ones are being discovered all the time. Just in the process of doing her doctoral work in Utah, she found 46 new species, and a new species of bee was recently verified in Central Park.

She began with speculation about how bees came into being back in the days of dinosaurs, when primitive magnolia flowers served as the stage where early predatory wasps could evolve into bees that used nectar and pollen for food. Making the transition easier was the similar nutrients content of insects and pollen.

Along with explanations of how to distinguish bees from other insects and from each other, she gave some insights into the myriad lifestyles bees have evolved: where various bees sleep through the night, and the underground preparations for spring.

I asked about how the presence or absence of various species of bees could affect habitat restoration efforts. She said that the first bee species to be lost when habitat is disturbed are the ground-nesting bees and those that are highly specialized and therefore specific about which flowers they pollinate. The specialist pollinators are highly vulnerable when the particular native plant species they've adapted to utilize are lost. Plant species reintroduced to an area after a long absence, and whose specialized pollinators have long since disappeared, will likely still get pollinated, she said, by generalists--bees that pollinate a great variety of flowers.

When asked about what to plant to accommodate the needs of bees, she listed three of the best plant families for attracting bees: sunflower (Composite), mint and pea families. I mentioned the phenomenal insect community (50+ species of insects and spiders) that comes together on our disks of boneset flowers each August, and a woman suggested that narrow-leaved mountain mint, a local wildflower found in meadows, also draws a very diverse insect crowd. Many posts having to do with boneset can be found on this website by typing the word boneset into the search box. Here's an example of the diversity to be found if one looks closely.

Some other notes:

• More bee diversity in dry climates, due to there being fewer fungi to prey on the bees. Southeast U.S., which has a hot, humid climate, has relatively low numbers of bee species.
• Carpenter bees use the same galleries year after year, enlarging them each time
• Bumble bees prefer abandoned rodent holes for building their nests
• Miner bees dig "gopher" holes in the ground. Most of their lives is spent underground. 
• Cuckoo bees parasitize miner bees, using a strategy similar to that of cowbirds. 
• Bee wolves paralyze bees and take them back to their nests for food

Master Gardeners of Mercer County are hosting a June 18 event on bees. 

One Good Garden Begets Another

A vision for attractive, low-maintenance curbside landscaping appears to be spreading across the municipal swimming pool's parking lot. The combination of mulch and perennials means little upkeep needed beyond an occasional watering.

The default lawnscaping still found elsewhere in the parking lot requires mowing, watering, and broadleaf herbicide, which I was told by a former rec dept director was necessary to keep white clover from growing. The clover flowers attract bees, which don't go well with barefoot swimmers.

The new garden looks to be the offspring of other gardens nearby. There's the Dogwood Garden Club's garden, here on the right, and Vikki's plantings in front of the parks and rec offices in the distance.

Vikki, a rec dept. employee, had already expanded her gardens beyond the walls and down towards the police department's parking lot. It's in the nature of well-tended gardens to expand, since the perennials benefit from occasional division, insuring lots of new plants that need new space to grow in.

At the other end of the municipal parking lot, another garden prospers, at Community Park Elementary. There's the edible portion in the front, and a more prairie-like garden in the back courtyard. Here, too, is a similar story of one garden inspiring another, until gardens now grow at all Princeton public schools.

A more detailed story of this greening of schoolyards--with Karla Cook, Dorothy Mullen, science teachers John Emmons and Martha Friend, and many other parents, students and teachers playing a role--can be found at the Princeton School Gardens website.

It may even explain what these cups signify--perhaps something to do with celebrating ten years of gardening at CP school.

Add to this the community gardens around the corner on John Street, overseen by the rec department, and one has a central example of a public gardening renaissance in Princeton.