September

Inescapably, September is a month of change and transition. Some aspects of September are highly predictable. The rapid decline in day length is inexorable, and we can’t help but mourn the disappearance of the many summer visitors, from hummingbirds to ospreys that retreat to warmer climes. Equally, we are cheered by the brilliant yellow of goldenrod flowers and, in the final days of the month, by the bright orange pumpkins that appear for sale at roadside farm stands and in grocery stores. The timing of other shifts is uncertain. We can be confident that the month will begin framed by the vivid deep green of late-summer tree leaves, but we cannot predict how many, or if any, of these leaves will start to senesce to yellow, brown, or red before the month is done. It all depends on rainfall, the depredations of insect pests and fungal disease, and whether we have any early frosts.

The first essay for this month of change is devoted to hummingbirds (“Rubythroats”), their presence in our summer backyard, and their September departure. I then consider two insects in turn: the Carolina grasshopper, which stays busy whenever the September sun shines warmly (“The Carolina Grasshopper”), and the elusive harvester butterfly and its meat-eating caterpillars (“The Hunt for the Harvester”). I conclude with a celebration of the quintessential plant of the month: the Canada goldenrod (“Goldenrods”). Somehow, this magnificent plant sums up the closing down of summer and signals the start of the countdown to winter.

Rubythroats

Here in New York State, we have one species of hummingbird, the ruby-throated Archilochus colubris. These wonderful birds arrive in mid-May and are gone by the third week of September, back to their overwintering world of Mexico and Central America.

The name ruby-throated comes from a patch of feathers, known as the gorget, at the throat of the male bird. These feathers are dark, almost black, but they contain tiny structures called platelets that are arranged in layers so that they reflect and refract light. If the light hits at just the right angle, it is refracted and appears . . . the most glorious ruby red. This is called structural color because there is no red pigment, nothing like the carotenoids that make male cardinals bright red all over. The male rubythroat with the biggest, most glittering gorget will win every dispute over territory, probably without a fight, and will win the biggest and best female. The females don’t have a ruby throat.

Ruby-throated hummingbirds never fail to amaze me. They are tiny, weighing just 0.1–0.2 ounces, the same weight as a lump of sugar, and they have a ridiculously long beak and short tail. Through the summer, they feed on the sugar solution in our hummingbird feeder nailed to a low branch of the red maple tree by our deck. This year, we have been particularly favored by a female. She perches quietly on the base of the feeder, green on her back and head, white with a little gray shading on the front. She dips her fine, black beak into the opening, surrounded by bright red plastic petals, then raises her head. She flies to a dead twig on the maple tree, where she remains perfectly still. About five minutes later, she returns for another snack of sugar solution. Then she is gone, flying swiftly straight over the privet hedge.

In those five minutes of perfectly still birdy meditation between the snacks at our feeder, the hummingbird is processing the sugar. This is tough internal work. She drinks enough to fill the bag-like crop at the front end of her gut. Before she can consume any more sugar solution, the first snack must be delivered, rather slowly, into her narrow, loopy intestines, where it is digested and absorbed across the gut wall into the bloodstream.

By September, the hummingbirds are crazy for sugar. In the week to ten days before they start their long journey south, they need to accumulate lots of fat and increase their body weight by up to 40 percent. There is no time or purpose to forage for insects and spiders during this period when their priority is to fill the tank with fat fuel. Our hummingbirds will soon be gone. Most likely, they will stop to refuel on their journey, especially just before flying across the Gulf of Mexico to their final destination in southern Mexico, Guatemala, or Honduras. A few individuals will sit out the winter in Miami or the Florida Keys. Whatever the details, their eighty wingbeats per second and one thousand heartbeats per minute make these tiny birds the ultimate gas guzzlers.

The hummingbirds are not only one of the migratory wonders of the world but also precision performers. The other day, we were eating lunch on the deck when a rubythroat came to the feeder. We could tell that it was a juvenile, and not our regular female, because it had dark speckling on its throat. It wasn’t settling at the feeder but hovered close to one plastic flower, then shifted sideways to the next, and so on, without feeding. Then it flew straight at us and hovered really close, close enough to touch. We could hear the hum of the beating wings: the reason why the first European colonists called them hummingbirds. Pursuing the hum a bit further, the hummingbirds’ base wingbeat frequency is about 40 Hz (toward the bottom of the piano range) with readily audible harmonics going up to about 400 Hz (close to the middle A used as the tuning standard at the start of a concert and about the same as the buzz of a female mosquito as she identifies me as her next meal).

Our hovering juvenile hummingbird wasn’t just humming. It was also making stabbing thrusts toward us and then backing off, all with perfect control, and it was calling a regular chip, chip, chip. We were glad that our eyes were protected by glasses because we sensed that this bird was very cross, out of its brains mad at something. Then there was a slight breeze and the bird returned to the feeder. Still hovering, it drank its fill. Our best explanation is that this young bird was frustrated with the wasps that were also enjoying the sugar solution. Perhaps the wasps left as the breeze rustled the leaves in the maple tree, leaving the feeder free for our adolescent hummingbird.

This is not weird behavior for a hummingbird. There are many reports of hummingbirds coming close to humans, even peering into a human’s face. Hummingbirds have excellent vision that is much more acute than human vision. It has even been claimed that they recognize the person who puts out the hummingbird feeder and bother that person if the feeder needs attention. Perhaps the chirps of our juvenile were intended to tell us about the wasps.

Proportionately speaking, hummingbirds have big brains, accounting for some 4 percent of their body weight (compared to 2 percent for humans). Please don’t get carried away by this percentage. The total brainpower of a hummingbird is less than ours. After all, hummingbirds can’t write about me and then press a button to deliver their scribbling to other hummingbirds anywhere in the world. But then, I cannot fly unaided to Mexico . . .

The Carolina Grasshopper

What a weird butterfly! It flies up, as if from nowhere, several yards ahead of me as I walk along the sidewalk or path, its wings flapping in glossy black with a fetching off-white band along its posterior margin. It flies purposefully in a curve or straight line, then zigzags as if struggling to decide exactly where to land, and finally drops down from a height of ten feet or more to a point farther ahead or to the side in the nearby vegetation. And then it’s gone. Sometimes, it is a singleton, but often, especially in a stubble field, approaching human footsteps can disturb clouds of the insects. They look like mourning cloak butterflies in desperate need of remedial flying lessons.

The weird butterfly is, of course, not a butterfly at all. It’s one of the band-winged grasshoppers, specifically the Carolina grasshopper (Dissosteira carolina). Despite its name, this conspicuous insect is widespread across most of the US and southern Canada.

When at rest, the Carolina grasshopper is nothing special to look at. It is quite big, up to two inches long, and a mottled dull brown-gray all over, providing perfect camouflage on the sidewalk, path, or any bare patch of ground. When the grasshopper prepares to fly, it opens its leathery front wings and unpacks its much larger, paper-thin black hindwings that do all the flapping work. That’s how the black-winged insect appears to come from nowhere. As it lands and swiftly repacks its hindwings, it returns to perfect camouflage. It is the classic startle-and-escape response that distracts and confuses any approaching ground predator.

At first sight, it makes little sense that the Carolina grasshopper spends so much of its time hanging around on the sidewalk in harm’s way, instead of hiding in the vegetation where it can munch in peace on its standard menu of just about anything green. The explanation is that, unlike many bees, wasps, beetles, and some flies, grasshoppers don’t indulge in the trick of shivering their muscles to warm up. For a Carolina grasshopper, getting up in the morning is a slow business, and the daylong progress with its to-do-list depends entirely on the weather. A cool, cloudy, or rainy day will find our Carolina grasshopper a sluggish mover with persistent fog in the brain, while a warm day with bright sunshine sees our grasshopper become an overachiever in its two all-consuming priorities of eating and making more Carolina grasshoppers.

There’s much to the task of making more Carolina grasshoppers. Like other grasshoppers, the male Carolinas use sound to advertise their beauty and prowess, but, unlike many grasshoppers, the Carolinas and other band-winged grasshoppers sing with their wings as they fly. The key to their alluring music is in their paper-thin hind wings, which are supported by stiff veins. When specific portions of the wing between two veins are stretched taut, they make a snapping or popping noise. No self-respecting lady could resist the elegant spread of black wings that go snap, crackle, pop. Biologists describe this romantic gesture with the ugly name of crepitation.

Of course, crepitation is just the start. True love can be a long-winded affair for Carolina grasshoppers; mating can last for twelve to sixteen hours. That’s it for the male, who presumably then has a relaxing bask in the sunshine and a large meal before he goes back to crepitating. For the female, it is just the start. Her next responsibility is to provision each of some forty fertilized eggs with a large gloop of yolk and some antifreeze and then stick her abdomen in the ground to make a shallow cavity. Lifting her abdomen slightly, she extrudes her eggs, which are stuck together with a maternal glue, into the cavity. She then covers her offspring with soil and smooths everything over with a delicate sweeping motion of her legs. The eggs remain underground and unattended until spring, when the youngsters hatch out and dig their way to the surface. Not all egg batches make it. They run the risk of drowning, being disturbed by a burrowing animal, or getting eaten by a hungry beetle.

And that would be the end of my story, except that crepitation is not the only nomenclatural indignity that our delightful Carolinas have to suffer. Far worse is that they are often referred to as Carolina locusts. This is a grave insult to these good citizens of the natural world. To explain, I need to go back to the beginning of the story. That’s some 55 million years ago, relatively soon after the dinosaurs went extinct. This is when the real McCoy grasshoppers evolved, probably in South America. They ate plants in the daytime, had prodigiously long back legs for hopping, and could fly. It was a winning strategy, and these guys—plus their many descendants—conquered the world. Generally, these grasshoppers are called short-horned grasshoppers (meaning they have short antennae) or acridids, and they are related to, but different from, crickets and katydids, which are also known as long-horned grass-hoppers. Alas for the rest of us, some acridid grasshoppers can build up enormous populations and then go on a rampage, eating everything in sight, occasionally forming massive swarms. I don’t mean dinky little swarms like swarming honey bees but swarms so large (up to billions of insects) that they can darken the sky for hours, even days, as the insects fly through. Acridid species that do this can validly be called locusts: the desert locust of northeastern Africa to southwestern Asia, the red locust of Sub-Saharan Africa, the Australian plague locust, the Central American locust . . . I could go on. These various locusts aren’t necessarily closely related to one another, but they are defined by their effect. Some (but not all) short-horned grasshoppers are locusts, just as some (but not all) plants are weeds.

To call the delightful Carolina grasshopper a locust is defamation. Carolinas rarely eat enough to upset humans, and they don’t swarm. The Wikipedia entry for this species vaguely alludes to Carolina-inflicted carnage, including “considerable damage” to crops in Saskatchewan in 1933 (I wonder whether the grasshopper was identified correctly) and declares that “there have been no detailed studies on [its] economic importance” (Wikipedia n.d.). Rubbing salt into the wound, several other grasshoppers, including the very common differential grasshopper, are regular and tiresome crop pests but are never called locusts. For the most part, the Carolina is an upstanding and mostly well-behaved short-horned grasshopper that does not deserve to be branded with the name locust.

The Hunt for the Harvester

The harvester is in a class of its own, in a manner of speaking. I will start with the qualifiers. The first is that there is nothing special about its place in the animal kingdom: class Insecta, order Lepidoptera (butterflies and moths), family Lycaenidae (meaning the blues and fellow travelers, see last essay of August). The harvester belongs to the fellow traveler category because it is not blue. It has orange wings with many large, rich brown spots, each ringed in white. It is pretty in its own way but rather small, just an inch across and, by all accounts, easily confused with a skipper. I should point out that I am describing the butterfly from pictures because I’ve never seen one in person. That’s one reason for the hunt. The other incentive to find this butterfly relates to its behavior, which is unique. I mean unique for North America, though not globally, and that’s my second qualifier for the harvester being in a class of its own.

It’s not the adult butterfly that makes the harvester special. Like other butterflies, its jaws have been converted into a flexible straw, called a proboscis. When not feeding, butterflies keep their proboscis rolled up below their head, a bit like a hose neatly packed on the side of a fire engine. When the butterfly alights onto a flower, the proboscis is swiftly unrolled, ready to probe deep into the nectary. The harvester adult has a proboscis, just like other butterflies, but it is very short. That seems odd until you discover that harvesters feed on the honeydew released from aphids. Honeydew is the polite word for the poop of aphids and other insects that feed on plant sap. Little honeydew puddles can often be found on the leaves of aphid-infested plants. As the name implies, honeydew is sweet, although it is generally more viscous and less easy to digest than floral nectar. It is an acquired taste. More accurately, it is a taste that has rarely been acquired by butterflies.

The real classiness of the harvester butterfly relates to the caterpillars. The adult female sets up her strange offspring by always laying her eggs singly on the branch of a tree that harbors one particular kind of aphid, a woolly aphid. The wooliness of the aphid is important to the story. These aphids are covered in brilliant white and often curly filaments, making them appear fluffy . . . or woolly. You could say that woolly aphids are the sheep of the insect world, except that aphid wool is made of waxes, which are highly complex lipids, not protein, as in the wool of sheep. Like sheep, woolly aphids flock together. The white, fluffy mat of the aphid flock looks like a fungal growth on the plant, and any insectivorous bird or carnivorous insect that suspects otherwise is educated rapidly by the noxious taste of the wax.

Woolly aphids lead a good life, except when a harvester butterfly lays one of her eggs nearby. The hungry little caterpillar that hatches out lacks the gastronomic sensitivities of most other creatures. It munches its way through the mat of woolly aphids and swallows the soft insides of each aphid, spitting out the wax-covered skeleton. This spitting out is done with great care and perfect aim so the waxy skeleton lands on the caterpillar’s back. Then the caterpillar extrudes a short thread of silk from its salivary glands, tying the aphid remains into place. Before long, the back of our munching caterpillar is covered in discarded bits of woolly aphids. The harvester caterpillar is like a wolf in sheep’s clothing, but not for long. That’s because it takes less than a week for the caterpillar to mature—far faster than other butterfly caterpillars that feed on plant material. But aphids are a superfood, as any ladybug, hoverfly larva, or chickadee knows.

The harvester butterfly has several generations each summer, and both the adults and their wolfish offspring are found all summer long—in principle. The complication is that this butterfly is highly unpredictable and not at all common. In our area, it favors the woolly alder aphid (Prociphilis tessellatus). During the summer, we kept our eyes open for the little harvester butterflies and colonies of woolly aphids on alder trees. I am referring here to the speckled alder Alnus incana, which predominates in our region both in mosquito-infested swamps, where it grows as impenetrable thickets and, more accessibly, as small trees on the edge of creeks.

Last weekend, we made a concerted effort to find the harvester. After all, the days are shortening, the leaves on the black walnut tree are starting to yellow, and it is often too cold for breakfast on the deck. In short, our days of butterfly hunting are numbered. More importantly for the harvester, the woolly alder aphids will soon be growing wings and abandoning the alder trees, returning to their winter quarters on the silver maple, where they will lay their overwintering eggs.

We traipsed along the section of East Hill Recreation Way that runs alongside Cascadilla Creek. The multiuse trail is broad and asphalted, and it is loved by runners, cyclists, roller skaters, and skateboarders, as well as by families with small children and dogs. At this time of year, the brilliant yellow of the dense stands of goldenrod and the bright purple of the asters under the basswood trees make the trail an especially cheerful place. Our task, though, was to spot the telltale leaf of alder trees that should be growing, here and there, on the creek side of the trail.

We scrambled down from the trail through the dense vegetation toward the creek. Just five yards from the trail, we found a different world. The water ran smoothly over the rocks and stones, two frogs jumped from the bank to the water—plop, plop—and a small, orange butterfly darted around. Then it settled, holding its fore-wings and hindwings at different angles . . . in the usual skipper way. There was no harvester butterfly here, nor was there any sign of woolly aphids on the alder trees.

We tried a second spot. I was briefly entangled in a thorny bramble en route, but it was worth it because the alders at the edge of the creek were particularly fine. What’s more, several mats of woolly aphids had taken up home on one of the branches overhanging the creek. Still, there was no sign of any caterpillars. We checked around. No small, orange-brown butterflies, either.

Perhaps we will have no luck this season. We’ll try again next year. As everyone says, the harvester is uncommon and unpredictable. In the meantime, we will look out for the pupal stage of the harvester on branches of alder trees. No one knows for sure how the harvester overwinters, but the pupa is the prime suspect. The pupa is a striking, bright white; is slightly elongated; and has two brownish blobs, as if eyes, above a more irregularly pigmented blob, as if an open mouth saying ooooh.

The hunt continues. . . .

Goldenrods

I suspect that, for many people, the word goldenrod conjures up an image of one species: the Canada goldenrod (Solidago canadensis). This tall plant with myriads of tiny, bright yellow daisylike flowers makes a wonderful show at this time of year, whether in our backyard, along unmown roadsides, or in unmanaged meadows and drainage ditches. It thrives in the full sun, attracting a zoo of different insects—bees, butterflies, beetles, flies, and more—that crawl from one tiny flower to the next and then fly to the next flower cluster, all collecting nectar and pollen.

We can think of S. canadensis as the house mouse or house sparrow of the goldenrod world. What I mean is that S. canadensis gets along with humans very well. It colonizes any patch of disturbed soil, thanks to its many, tiny windborne seeds, each of which can potentially germinate, take firm root, and spread by its underground rhizomes to form dense, impenetrable monocultures. Individual clumps can persist for a century or more. To keep the goldenrod in our backyard under control, I go on patrol every spring, spade in hand, and dig up any plants that have escaped from the designated goldenrod patch. Some of the escapees have diminutive roots, but many sport strong root systems with long, pink-white rhizomes.

S. canadensis differs from house mice and house sparrows in one important respect: although humans tolerate or resist the mice and sparrows, they tend to appreciate S. canadensis. So much so that, a mere twenty-five years after the Mayflower brought the Pilgrim Fathers to North America in 1620, S. canadensis seeds were transported in the reverse direction to be sold to English gardeners. It appears that nothing much happened, or people didn’t notice, until the Victorians decided that every flower border must include a patch of S. canadensis goldenrod. By 1849, S. canadensis had escaped from gardens and was flourishing in the British countryside. Gardeners across continental Europe and in temperate Australasia were similarly beguiled by the golden beauty, and goldenrod was introduced, for example, to Russia in the 1700s, Germany in 1857, Poland in 1872, Australia in 1935, New Zealand in 1940, China in the 1950s, and Japan in the 1970s.

Everywhere, S. canadensis has responded to the hospitality by running amok. There have been various attempts to shut the stable door after the golden horse had bolted into wasteland, native meadows, pastureland, forestry nurseries, and wetland edges. However, the stable door remains open in many countries, where ornamental goldenrod can still be purchased for gardens. Some of the plants available in garden centers and by mail order are said to have been bred to be more showy and less invasive, but I am astonished that people are prepared to take the risk.

One of the chief routes to modify the goldenrod for gardens is to use hybrids between S. canadensis and other goldenrod species. This takes me back to the beginning. The common perception of goldenrod as a single species is totally wrong. Come to North America and enjoy the task of discriminating among nearly one hundred species, including twelve that flourish in the meadows, woods, swamps, and roadsides around Ithaca.

Everyone agrees that North America is the center of diversity for goldenrods. There is just one native goldenrod in the UK, Solidago virgaurea. We can’t call S. virgaurea the “British species,” though, because it is exceptionally widely distributed throughout Europe, extending into Asia and North Africa. S. virgaurea is half the height of S. canadensis and bears flowerheads of small yellow flowers. To be honest, it is no beauty; it is as exciting as a ragwort. Even more mortifying, S. virgaurea and the invasive S. canadensis have ignored their description as different species. They hybridize rather readily, and the hybrid, known as S. x niederederi, produces viable seeds and has been reported in most European countries, including the UK. So far, it doesn’t appear to be highly invasive, partly because it lacks the rhizomes of its North American parent. Perhaps we should be watching that space.

At this point, I want to digress briefly to John Burroughs (1837–1921), a naturalist who wrote persuasively and at length about the environmental and spiritual importance of the natural world. A few years ago, we visited his home, a farm in West Park, in the Catskills. It was late summer, and the meadows were ablaze with goldenrod. Burroughs was an astonishingly influential person. Important people, including President Theodore Roosevelt, paid attention to everything he said and wrote. In particular, he was great friends with industrialists Henry Ford and Harvey Firestone and with the inventor Thomas Edison. This gang of four called themselves the Vagabonds and went on camping trips together, where they thought great thoughts and solved the world’s problems.

All of this is relevant to goldenrods. The story starts with Thomas Edison. He was bothered that the supply of rubber from Southeast Asia, which was needed by his pals Ford and Firestone, might be cut off by political uncertainties, and he experimented with various alternative sources of the product. Goldenrod was by far the most promising. Edison bred a twelve-foot-tall high-producing variety. When Ford gave one of his cars to Burroughs, he arranged for the tires to be constructed from goldenrod rubber. Unfortunately, Ford’s plans for commercial goldenrod rubber production came to naught, just as his prototype car made of soy-derived plastic instead of steel failed to reach the factory floor.

I can’t help but wonder whether the wheels of fashion and need will turn again. One day, goldenrod may be developed as a sustainable source of rubber and other latex-derived products, building on the groundwork of Edison and friends.