If you had a chance to save a piece of the natural world and all you had to do was flip a switch, would you do it? Believe it or not, many of us have that power at our fingertips. For example, if you have nightlights on the perimeter of your property and turned them off or put them on a motion-sensor trigger, you would add to a feature of suburban life that is fast disappearing—pitch darkness. Instead, so much in the summer night seems to be illuminated, to the detriment of clearly seeing the stars, planets, and the August meteor showers at night, but also some of the most spectacular creatures on Earth.
One such species frequents our backyards and woodlands, The Prometheus moth, named after the Greek God who gave humans the gifts of fire and wisdom. Its food plant is the most common woody shrub found along the banks of the Potomac River, spicebush (Lindera benzoin), a member of the laurel (or avocado) family. The leaves and bright red fruits of spicebush are incredibly fragrant especially if, like me, you think of a turpentine aroma as a kind of natural perfume. The fruits, rich in lipids, are a favorite of birds heading south in early fall. The leaves are just as aromatic and in many ways also serve as a caterpillar fast-food outlet for two of our loveliest flying insects. On some of the leaves you can find the caterpillars of the spicebush swallowtail, a beautiful metallic blue butterfly (previously covered in this column). Another fan of spicebush leaves is the stunning Prometheus moth (Callosamia promethea), measuring over four inches in length. The feathery antennae are typical of the species in this moth’s family, the Saturniids, which includes more than 1,300 species, mostly tropical. But it’s the wings that are works of art, especially in the female, with a palette of rich reddish-browns highlighted by a black eye spot in each wing. The male is more subdued in a tuxedo of dark charcoal trimmed in tan.
You are much more likely to see the spicebush swallowtail than the Prometheus silk moth because the brilliant female is only active at night. In fact, that is one common way to separate moths from butterflies—moths fly at night and butterflies fly during the day. There are other distinguishing features: butterflies typically have little clubs at the end of their antennae and moths have anything but clubs. There are exceptions to these rules, as nature’s way is to create exceptions to virtually every rule as a byproduct of evolution by natural selection. As if to highlight this point about nature’s never-ending exceptions to the rule, the Prometheus moth is the only known member of its family where the males fly during the day and the females only fly at night (the males and females do overlap briefly in their activities at dusk in order to mate). How do male Prometheus moths avoid predators in the daytime? By mimicking a type of butterfly, the poisonous pipevine swallowtail, a cousin of the non-poisonous spicebush swallowtail.
If the creator had an inordinate fondness for beetles because he made so many of them (numbering around 330,000 species), as noted in a previous column, some such fondness must also have been showered on moths along the way. We think of butterflies as super diverse, with about 17,500 species, yet that is but a speck in the butterfly net compared to moths, of which about 160,000 species have been identified, just half the number of beetles.
Human urban dwellers have unfairly attributed an ignoble reputation to these diverse creatures because of the clothes moth, whose preferred habitat is the beloved cashmere sweater in the drawer (with food stains on it), or the pantry where grains are stored. But once you are out in nature, the variety and beauty of moths is plain to any nighttime beholder. Instead of the dull gray-brown of indoor moths, the Saturniids and other giant moths are some of the most attractive of all insects.
They also have an outsized role to play in three main areas. First, and most narrowly human-centered, certain moth species have been cultivated for centuries to produce silk for the finest clothing and carpets. Second, and of considerable ecological importance, far more species of plants are pollinated by moths than by butterflies, and many flowering plants have evolved unique signaling mechanisms to reel them in. Moth-pollinated plants produce the flowers that open only at night and have strong, often pleasant aromas. In the cloud forests of Costa Rica, I’ve had the privilege of seeing one species of moth, the hawk moth, visiting a flowering plant in the nightshade family with a flower eight inches long. Nectar puddles at the base of the corolla of this plant, called Solandra, attract the hawk moth, its only known pollinator, which reaches the nectar with its extraordinary proboscis, which is just over eight inches in length when unfurled. But even many plants that flower during the day keep their flowers open at night and the nectar flowing to take advantage of the abundance of moths. Third, and also ecologically important, is the role of the moth in the food chain. Moth caterpillars have been described as tubes of protein, so vital to the menu of our beloved backyard birds. In the late spring and summer, caterpillars are a featured item in the diets of warblers, vireos, catbirds, and all our other backyard singers that can locate them. Adult moths, after they emerge, are a mainstay for our local bats, that themselves also help us by keeping down the populations of mosquitoes when not feeding on moths.
So why do we need to turn out the lights at night? The lights attract moths and the light pollution of our suburban landscapes may cause them metabolic stress and cellular damage. In many cases, these lights are unnecessary. If you must have outdoor lights, please consider buying motion-sensor activated lights. These are more likely to scare off intruders by adding the element of surprise than lights that stay on all night. And if we all turn off unnecessary lights, another lost treasure might reappear—the multitude of stars visible agai on a clear night.
If you have kids and want to turn them on to the diversity of nature, or reawaken the kid in you, go purchase a black light on the Internet, and on a warm humid moonless night, put a white sheet over your black UV light and be amazed at the moths that appear. You might even come face-to-face with Prometheus.
By Eric Dinerstein
Illustration by Trudy Nicholson