Marcescence – the art of not letting go

I think this is the alpine hairy cap moss, Polytrichastrum alpinum
I think this is the alpine hairy cap moss, Polytrichastrum alpinum

I was in Denmark, Maine, this weekend doing very Maine things. Shoving sclerotized sunshine (wood) into the belly of an iron wood stove. Walking alongside a mountain brook with moss-covered rocks licked with a verglas (ver-glaze) of ice. The verglas an art of steely-eyed primeval monsters frozen in time or a hundred fingers overlapping each other to grip the rock. For a time the ice held my imagination as it held the rocks.

I, for the first time in my life, enjoyed a superheated sauna. And once my body reached the right temperature, a local convinced me to jump in an icy brook. The mercurial abuse I gave my body made me superhuman. It detoxified my spirit and I bravely walked in the nighttime air shirtless, immune to deep fall’s icy breath. It was the crunch of snow under my tender feet that reminded me that I was a mortal.

Absorbing the painful joy of steep hikes on a snow-dusted mountain, I took in the tinkling spread of sunshine of moss that held tiny bits of ice, like tinsel on a tree. It was the American beech (Fagus grandifolia), however, that drew most of my attention. On its branches were papery brown leaves – leaves that will loiter on the branches all winter unlike the rest of the foliage that was now underfoot. Marcescence is the term for deciduous trees that do not shed their leaves though they’ve lost their color. Throughout the mountainside was a forest of leaves that refused to fall despite the namesake of the season.

American Beech, Fagus grandifolia, Denmark, Maine (1)

The American beech. Onto its leaves it holds.
The American beech. Onto its leaves it holds.

The hypotheses about why a tree may keep its leaves throughout the winter range from deterring the nibbling deer to preserving its nutrients. I am too lazy to do the research on the science of marcescence. Fortunately, my good friend David Haskell (another great wordsmith scientist) has done that work already.

I have my own marcescence, hanging onto things that I should have long ago shed. In my closet loiters a pair of jeans that I won’t wear because they are more holes than jeans, but keep because they are extremely comfortable. I say I will fix them one day. No. No, I won’t. I should dispose of these vagrants.

My mind holds onto memories that I don’t need. From worthless minutiae about the fact that I had only one egg with my pancake last Wednesday (I only had two eggs left and I broke one of them trying to flip it for over-easy and I threw it away frustrated – why do I need that taking up space in my brain?) to painful memories of anger. Of recriminations. Of hurt and of heartache.

And it is my heart that is the guiltiest of marsescence. I have lingered too long in relationships where we enjoyed a hopeful spring that erupted into a frenzied summer that then reached a fall withering. In the winters of those relationships I have held onto the leafy reminders of those summery days, hopeful of their return when I should have let those dead leaves drop.

It is not yet clear why the leaves of the beech do not drop. Maybe the beech is like me. It simply cannot let go.

And the winner is…

Galloping hordes of marsh snails!
Galloping hordes of marsh snails!

I have just returned from the New England Estuarine Research Society meeting in Groton, Connecticut (don’t be jealous). One of my students, Bethany Williams, gave a talk on the coffee-bean snail, Melampus bidentatus, and the effect of sea-level rise. I don’t want to give any spoilers, but as the salt hay in the Great Marsh is lost as sea-level rises, it could be bad news for the snail. But in sunnier news, Bethany, an undergraduate from Florida State University, gave her first talk ever and won best Undergraduate Oral Presentation! Very exciting! Congratulations Bethany!

Bethany's first scientific talk, NEERS, Rankin Prize Winner (11)

Below is time-lapse video of snails moving in and out of an abandoned footpath in the marsh. It demonstrates how snails avoid the path during the daytime heat, but when the temperature lowers and the humidity rises they gallop out from the grass to gobble the algae in the open. When the sun (and the heat) returns they ebb back into the grass. It’s a cool video that demonstrates potential impacts of climate change on these, turns out, sensitive snails. When Bethany’s thesis is complete, we’ll post more of the story. For now, enjoy the video.

To be a bee or not to be a bee? Oh. Mimicry.

A fly takes a sweet drink
A fly takes a sweet drink

A warm mid-October day has invited the flies and the bees to get a last sip of supper from the white daisies that bob their heads in an autumnal zephyr. The six-legged sippers dance and swirl on a yellow stage of the flower disks at the center of the white-petal apron. The tongues and siphon mouths probe each floweret for nectarel treasure. I pull out my camera to sip the nectar of the scene. I focus on a fastidious honeybee who doesn’t mind a close-up, or is too concentrated on tasting each floweret to notice. I watch her letter-opener of a tongue plunge and retract. The large, dark oval of her eyes are set on either side of her fuzzy head of dingy yellow hairs. The wings attached to the fuzzy tennis-ball of her thorax. Her abdomen appropriately the color of light-honey. She hop-flies to another flower.


I find another bee.


She is turned away from me so I only get a shot of her abdomen and wings. I change my angle. Another shot, but still not her head. A few more shots and she turns to me. My mind tells me something’s not quite right, there is a subtlety of appearance that my mind can’t reconcile. Then with the clarity of focus, I see it. Instead of two eyes set on the side of the head, two eyes cover most of the front head like grossly-oversized aviator glasses. I look at the insect again carefully. The abdomen is darker and wider than the honeybee’s. The thorax is fuzzy, but not as hirsute as the bee’s. I am not looking at a bee. I am looking at a fly wearing a honeybee costume. This is the hoverfly, Eristalis tenax.


In a gathering of flies, the hover flies almost always show up in costume. This may startle guests because the hover flies are costumed as bees and wasps.


In its history, the hover flies have co-evolved with their hymenopteran kin to mimic the motorcycle sleek vespid form of the wasps or the fuzzy patterns of the bees. The hover fly not only mimics the bees and wasps, it also mimics its behavior to clearly signify its bee-ness. The advantage of this mimicry is that other species conduct themselves around a harmless dipteran as though it was a stinging, noxious hymenopteran. The fly gets the benefit of the protection given to a behavior and a pattern that announces danger, without the energetic investment into poisons and stingers.


Had I not taken the time to admire the bobbing beauties of the daisies and their six-legged sojourners, I would have simply assumed all the ‘bee-looking’ insects were indeed bees and been careful to avoid an injection from an agitated nectar forager. My childhood lessons of Ozarkian ecology in Arkansas taught me to avoid danger signs. Many a harmless watersnake, which are not pit vipers but look like cottonmouths, which are venomous pit vipers, did not find itself in my hands because I dared not get close enough to its face to see if it had pits or a cottony mouth of white.


Being a harmless animal while looking like a dangerous one is called Batesian mimicry and is thought to protect mimics (in this case the fly) from predators who have learned the danger of attacking the model (in this case, the bee). Danger-bluffing may also confer a competitive advantage in the search for food. Bees and wasps can be aggressive and attack other species, particularly during foraging forays. As a result, less aggressive species are less likely to land on a flower already occupied by a hymenopteran bully, or what it thinks is a hymenopteran bully – such as the hover fly. Thus, a hover fly can dine at the daisy’s dinner table with plenty of elbow room.


As I watch the fly use its permanent Halloween costume to trick others so it can delight in floral treats, I am confused further. The honeybee is the European honeybee, Apis millefera, which arrived in the United States with the English colonists in the 1600’s. 400 years is not nearly enough time for an American hover fly to adopt the fashion of a European bee. Later I learn that the hover fly is the European hover fly and introduced to the U.S. in the 1800’s. It was, therefore, in Europe that the hover fly, like an evolutionary little sister who wants to do just as her big sister does, began following the honeybee’s fashion sense. It was to the hover fly’s benefit to arrive after the honeybee because the bee-costume might not have worked. Mimicry is predicated on predator’s learning which color patterns are danger and which are food. Without the stinger of the honeybee first arriving, predators would have gobbled up the bee-looking fly.




I have since learned that I have met this fly before, and it was wearing a more grotesque costume.


While sampling for invertebrates in a salt marsh pond in Ipswich a new form caught my eye among the wriggling fish, the water beetles, and the dragonfly larvae which look like flattened, alien grasshoppers. A small, dirty white pill of a maggot with a tail twice as long as its body whiplashed awkwardly at the bottom of the bucket like an anemic sperm. I held it in my hand, fascinated by its strangeness and slightly disgusted by its maggotiness. I had heard the term ‘rat-tailed maggot’ before and what wallowed in my looked both rat-tailed and maggoty. I failed to confirm the identity once I returned to the lab. Had I done so, I would have found that I was holding the larval stage of the hover fly.

Upon reflection, it’s strange to find fly larvae in the marsh ponds, which is not an easy way of life. It’s incredibly briny and low in oxygen. For the hover fly, however, a marsh pond is perfect habitat as they thrive in low-oxygen pools and sewage lagoons regularly. And on occasion, in the anus of bipedal mammals who drink water infected with drone-fly eggs.

The maggot is able to live in fetid habitats because the ‘tail’ is a snorkel that it can periscope above the filth for fresh air. Like the mosquito, the low oxygen of tire water, a sewage lagoon, or a marsh pond is not a problem because it gets oxygen from the air, not the water. This also permits the maggot to take up a rectal residence. The snorkel protrudes not only from its anus, but also of the host.


We’ve come a long way from the florid prose of daisies of the beginning of this essay, haven’t we?


In its evolution, the hover fly has dabbled in two interesting life strategies. As a larva, use a long snorkel so you can live in habitats that most would not dare to occupy. As an adult, don a mask of venom without investing in such.



I have returned to the daisies. Today is warm again, hot even at 73 F. The hungry mouths of flies and bees and flies that look like bees lap at the daisies. Today’s warmth mimics that of late summer. But, as with the hover fly, there are clues that signal the autumnal truth. The trees are flashing their oranges and reds and yellows like slow turning stoplights. The daisies reside here at Tendercrop Farm and on every shelf of the outside patio orange pumpkins have blossomed. The calendar tells me that in two weeks many of us will wear a costume and a mask to hide the truth of ourselves for a day.

But, if you’re like me, some last longer than a day.

I consider the masks I wear. The mask of bravado and humor for my sister and brother and mother. One that hides the anxiety and fear. The mask of knowing in a conversation with a colleague or superior to hide my blatant ignorance. The tense smile and ‘It’s okay,’ to hide my utter frustration and irritation with a partner. I costume myself in these lies for the same reason the hover fly wear’s its bee-costume, for protection.


Okay, let’s play a game. Which is the bee and which is the fly? If you hover your mouse over each pic it will tell you the answer (look in the bottom left corner of your screen).

Honeybee, Apis millifera, Newbury, Massachusetts (3)

European hover fly, Eristalis tenax, Newbury, Massachusetts  (2)

European hover fly, Eristalis tenax, Newbury, Massachusetts  (1)

Honeybee, Apis millifera, Newbury, Massachusetts (7)

European hover fly, Eristalis tenax, Newbury, Massachusetts  (4)

Honeybee, Apis millifera, Newbury, Massachusetts (1)

Go ahead and peep. I won’t tell.

Unknown ornamental, Newbury, Massachusetts (2)
A magnificent ornamental beauty along Route 1 in Newbury.

The North Shore, Massachusetts

The autumnal paintbrush has dabbed the trees here north of Boston. The red maples scream, me first, me first with their red and sometimes ghostly oranges – colors I cannot adequately describe nor capture on film. For those of you who can’t make it up this way for a little leaf peeping (it’s a thing), here’s a tour.

But first! Science.

Leaves change colors because the chlorophyll (the light-harvesting pigment that makes leaves green) is being broken down and its nutrients, particularly nitrogen are being packed into the tree to overwinter. The colors are other pigments that were there all along (in most cases), just overshadowed by chlorophyll. Now is there time to shine. Below is a great graphic that explains the most common pigments you see.

A great graphic from: Check them out for other cool stuff!

Oh, and if you want to see pictures of maybe the biggest, oldest organism on the planet (hint: it’s a tree), see here.

And now pretty, pretty pictures. Go ahead and peep. I won’t tell.

At the corner of Route 1 and Glen Street, Rowley
At the corner of Route 1 and Glen Street, Rowley

Fall colors, Rowley, Massachusetts, Oct 2014 (2)

Red. Asphalt.
Red. Asphalt.
Cemetery colors, Oak Hill Cemetery
Cemetery colors, Oak Hill Cemetery
Cemetery colors, Oak Hill Cemetery
Cemetery colors, Oak Hill Cemetery
Even the lichens like to show their colors
Even the lichens like to show their colors
Picture taken in 2013 on Newman Road. The sugar maples, shown here, have not yet turned the road into a golden tunnel so you still have time to see some great color! You've got three weeks!
Picture taken in 2013 on Newman Road. The sugar maples, shown here, have not yet turned the road into a golden tunnel so you still have time to see some great color! You’ve got three weeks!

Pantyhose ingenuity

How would you catch this dragonfly?
How would you catch this dragonfly?

In the fall of 2012, I was to teach entomology at Sewanee: University of the South, whose campus is 13,000 acres of largely undeveloped forested land on the Cumberland Plateau. All about Lake Cheston dragonflies maneuvered like jet fighters. I didn’t know how to catch these lightning-fast aerialists. Field guides offered no suggestions, but the scientific literature did: shotguns.
From a 1972 paper by T.M. Neal and W.H. Whitcomb in the Florida Entomologist, “High flying…dragonflies were shot down with a 20 gauge shotgun; the shot in the shell replaced with fine sand.”

I immediately asked my colleagues what they thought about letting my students use shotguns on Sewanee’s 13,000 acre campus to collect dragonflies. My colleagues were, I’ll say, intrigued by the idea, but said I’d have to get approval from the administration for my ‘shotgun pedagogy.’

Could I really get the University to not only buy shotguns as an entomological supply, but also let the students blast bugs out of the air?

I don’t know what the answer because I never asked the administration. I thought twice about arming my students with shotguns and instead armed them with nets and traps and cameras. The dragonflies, and likely the faculty, are probably better for it.

But I really liked the ‘shotgun ingenuity’ of Neal and Whitcomb’s approach. I imagine them sitting around beers saying, “How are we going to catch these things?” And then Whitcomb suggests, half as a joke and half serious, “What if we blasted them with a shotgun?” They both laugh and sip their beers. Then they both get quiet for a moment. Then Neal says, “You know, if we pepper them with a smaller shot, it might just work.”

Field biology and ecology requires a large number of tools, but the most important one is ingenuity. Often there is not a ready-made, manufactured piece of equipment for your particular needs. A field scientist must be able to think on his feet or engage in what I call, ‘shoot-from-the-hip-ecology.’

One of my own moments of ‘shotgun ingenuity’ came in 2007 when I was conducting an experiment where I needed to keep grasshoppers in cages in a salt marsh to determine how many grasshoppers it took to severely damage plants. But first I had to catch hundreds of grasshoppers. The problem is, how do you put 100 grasshoppers into a bucket without some escaping every time you open the lid to put one in?

Let’s go to that moment:

Prarie grasshopper (Melanoplus sp.) in the saltmarsh. Plum Island Estuary, Massachusetts
The quarry: a prairie grasshopper (Melanoplus sp.) in the saltmarsh. Rowley, Massachusetts

July 2007
The Great Marsh
Rowley, Massachusetts

The grasshoppers thumped like popcorn in the five-gallon bucket. I had 10 but needed hundreds more. Every time I opened the lid to put one in, two jumped out. I needed to be able to add grasshoppers to the bucket without opening the top.

I wandered around the local Kmart and found the answer in hosiery. Pantyhose.

I stared at the pantyhose size chart which was some sort of cryptogram that correlated letters to weight. I tried to figure out how much I would weigh if my legs were the size of five-gallon buckets. Would I be a B or a Queen Petite or a Queen 2? It depended on how tall I was.

Not able to crack the code I asked a sales associate.

“Excuse me. I’m trying to put pantyhose on a five-gallon bucket. Can you help me figure out what size I need?”
She asked immediately, “On a bucket?”
“It’s for grasshoppers,” I said as if that explained it all.
“Grasshoppers?” she asked.
“I’m a scientist,” I added.

Possibly not wanting to hear anymore cryptic answers she consulted with me about sizes. She also taught me about control tops and the different colors (nude, taupe, black!). She told me the difference between pantyhose (which go to the waist), stockings (which go to the thigh like long socks), and leggings (long socks with no feet). So many grasshopper options!

After some experimentation, I found that the best fit for a five-gallon bucket was a queen size control top. Stretching the waist over the bucket top and cutting off one of the legs let me plunge my closed fist holding a grasshopper into the bucket, release it and pull my hand out without the grasshoppers escaping. It also allowed for sufficient airflow and temperature regulation, which minimized mortality during collection.

The scientific term is:  orthopteran retention vessel. Or a bucket with pantyhose on its head.
The scientific term is: orthopteran retention vessel. Or a bucket with pantyhose on its head.

The significance of the result of my ‘pantyhose ingenuity’ can be found here. The data on the difference between ‘taupe’ and ‘nude’, however, remain inconclusive.

Have you used ‘pantyhose ingenuity’ in your own work?


Underwater walking

I wade into a marsh pond and see a funny speck of dirt crawling on the surface of the water. But on the underside of the water’s surface . And it’s not dirt, but a minute snail from the family Hydrobiidae. This particular snail is not content enough to walk with its stomach foot on the ground or the plants, but to fancy itself on the underside of the water’s surface.

If you are small of mass, gravity pulls on you very weakly. If you are small enough and a snail, you can spread your stomach-foot out wide and can take advantage of the water’s surface tension to walk on the ceiling.

But first you must get to the ceiling. This minute snail can simply crawl up the side of the pond bank or a plant stem. Or create a tiny bubble of air to carry it up to the water’s surface. Often they will do this when it gets to crowded on the bottom. How nice it would be to simply create an escape bubble anytime you were uncomfortable.

I cannot walk on water, on the surface or underneath, and my legs create tsunami sized waves relative to the tiny water-walker as I walk. The snail’s grip on the surface relinquished and it sinks awkwardly to the bottom, like a coin dropped in a bucket of water. Now it must decide how comfortable it is and whether to stay on the bottom, or rise to the top.