“Settled in Quivering Contentment”
The Elegant Adaptation of the Primrose Moth
Like most of you, I spend my summer leisure time contemplating the proboscis of the Primrose Moth, which is about half the length of its body.
That anatomy alone might be enough to kindle your interest in this insect. But now consider that the Primrose Moth is Pepto-Bismol pink with a lemony margin at the tips of its wings. In that pink presentation and probing proboscis, the Primrose Moth offers us a lesson in form, function and evolution by means of natural selection.
Primrose Moths (Schinia florida) fly around searching for the Evening Primrose (Oenothera biennis), a common garden and roadside plant with a dangling, elegant yellow flower. The primrose flower opens at night to the moth, and then usually closes by day. So a moth lingering in the flower until dawn gets an intimate embrace of petals.
Besides the hug, the moth gets nectar. I’m not actually sure what the plant gets out this deal. The moth doesn’t appear to pollinate Evening Primrose, according to botanists and scientific literature published on this particular encounter of insect and plant. In fact, the moth seems to get the best of this relationship. The female lays her eggs on the Evening Primrose, and when the caterpillars emerge they start munching the plant where it hurts: the flower buds.
In any event, most of the action happens at night, when the primrose springs open its flower and the moth plunges head-long into the blossom. Even so, alert flower watchers among us can now witness, in broad daylight, this meeting of moth and bloom. Buried in a blossom after a night of binge-nectaring, the Primrose Moths are like a drunk passed out at the bar at dawn.
But this encounter also turns out to be an example of the struggle for existence and the shared evolution of insects and plants. Those pink wings are often buried out of sight in yellow flowers (as in the banner image above). The portions still visible are the trailing edges, the yellow edges, which conveniently resemble the yellow edges of the primrose petals. The moth has evolved with camouflage so that it can sit and drink nectar, presumably unnoticed by predators.
One of my favorite naturalists, William Hamilton Gibson, says we can hardly know the Evening Primrose until we know its nighttime visitor. Gibson was an exuberant 19th century writer and illustrator. In his 1892 book “Sharp Eyes,” a collection of essays and illustrations through the seasons (which you must own) Gibson revels in the moth and its blossom:
“Is this a mere withered, useless blossom that droops upon its stem? Is it not rather the prettiest luminous fairy tent that ever sheltered a day-dream? Last night, when its four green sepals burst from their cone, and sprang backward to release their bright, glossy petals, a small moth quickly caught the signal, and settled in quivering contentment, sipping at its throat. Its wings were of the purest rose-pink, bordered with yellow.”
“In the color of its marking, we find an outward expression of its beautiful sympathy, the yellow margins of the wings which protrude from the flower being quite primrose-like, and the pink being reflected in the rosy hue which the wilting primrose petals so often assume, especially at the throat.”
Did you catch that “beautiful sympathy?” First, the yellow match: wing tips and petal. But there’s another: a wilted primrose flower turns pinkish. So a primrose moth merely sitting on the stem of the plant may resemble an old flower and still find safety in the color pink. Evolution by means of natural selection (or so I assume).
What we cannot see in this little drama is the moth’s proboscis lapping nectar from the base of a primrose blossom. But we might deduce it. Take a close look at the flower at the upper left in the botanical illustration above. Below the base of the petals, the flower has a long, slender tube called the hypanthium, a long reach for a moth seeking nectar. No matter. In nature form follows function. The moth unfurls its built-in drinking straw for a sweet reward in that hypanthium.
So, this August, get your own sweet drink to go — and enjoy it in the good company of an Evening Primrose and its illustrious visitor. If you find one, and are so inclined, send me a photo. I’ve created a gallery of your images below.