When a Goldenrod Flower Moves with Intention 🐛

The Caterpillar in the Florets

I was inspecting the flower clusters of sweet goldenrod (Solidago odora) at Hatches Harbor, looking for galls. At this time of year, I often linger over the flowers because so much is happening at that scale. A goldenrod inflorescence is not simply a display of yellow. It is a small, crowded habitat: pollen and nectar, developing seed, insect eggs and larvae, predators, parasitoids, gall makers, and innumerable lives that find food or shelter among the florets.

Then one flower cluster moved.

Not with the larger, shared sway of wind moving through the goldenrod. This was a smaller, uneven motion, a twitch that seemed to belong to one small piece of the inflorescence. Looking closer, I realized that the “florets” were partly an animal.

I am leaning toward a camouflaged looper, perhaps the larva of the wavy-lined emerald moth (Synchlora aerata). The caterpillar itself appeared yellow beneath an extraordinary covering of borrowed goldenrod. It had clipped small pieces of its host plant and attached them to its back, making a costume from the very florets in which it fed. The result was not merely camouflage by color. It was camouflage by construction: a caterpillar becoming, in outline and texture, a loose little cluster of goldenrod flowers.

Camouflaged loopers are geometrid caterpillars, or inchworms. They are known to clip flower fragments and foliage, fastening them to raised projections on their backs with silk. Goldenrods are among their host plants.

The costume is not permanent. When the caterpillar molts, moves to a different host, or finds that its existing disguise no longer matches, it replaces the decoration. What looks from a distance like passive imitation is an ongoing behavioral practice: cutting, carrying, fastening, and replacing plant material.

By the way, I found the flower galls I was looking for, consistent with Schizomyia racemicola, the goldenrod flower gall midge. I also found a little party of three small bees, possibly Andrena species, still sleeping, clumped tightly among the goldenrod florets on another stem. Another story for another time.

I had set out to find evidence of an insect reshaping goldenrod into a cluster of galls. I found that, but I also found a caterpillar remaking its own exterior from the plant: becoming, for a while, a moving piece of flower. And the giveaway was not shape or color, but motion that did not belong to the wind.

📷 Wavy-lined emerald (Synchlora aerata) | © Claire O'Neill, please credit accordingly