Life on the Leaf Edge
A series of six expertly disguised prominent moth caterpillars
- Finned Prominent
- Black-etched Prominent
- Checkered-fringed Prominent
- Wavy-lined Prominent
- Double-toothed Prominent
- White-blotched Prominent
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The long summer has taken its toll on a once lush New England leafscape. What was initially strong, green, and uniform is now decorated with burnt withered edges, pot-marked with spots of fungus and decay, speckled with the galls of tiny insects, and fragmented after a sustained onslaught from a myriad of herbivores. The perfect leaf image that we might hold in our minds rarely exists in nature, instead we find that any stand of late season foliage is a war-torn mosaic of consumption and infection.
As the year winds on and the leafscape matures, the diversity of color and texture in our natural environments dramatically increases. Compared with the crisp and uniform freshness of spring, the decay of fall provides a far more varied and interesting biological backdrop. It is in relation to this backdrop that many of our more incredible native caterpillars have evolved.
The series "Life on the Leaf Edge” shows but a small selection of our many remarkable leaf-mimicking caterpillars. These six caterpillars all belong to a group of medium sized moths called the prominents, a group that arguably contains this region’s most finely tuned leaf-mimicking organisms in both form and behavior.
The finned prominent is a spectacular caterpillar when seen in isolation and it can be hard to figure just how its camouflage functions. That is, until one observes the many dry, gray, and wrinkled edges on the leaves of a water starved big-toothed poplar sapling.
Resting along an arching leaf petiole, the black-etched prominent is a convincing mimic of a partially eaten willow or poplar leaf. But these caterpillars do not rely solely on their camouflage for protection. When disturbed a black-etched prominent's forehead flushes bright red with faint black eyespots and its already long spiny black tails inflate to many times their normal length with bright red, yellow, and white patterned filaments. Head held high, jaws spread wide, tails flailing and dancing above their backs, these prominents are clearly sending a threatening message to would-be attackers. I'm just not sure what they are saying!
The checkered-fringed prominent is at home when nearby to any sun burned and damaged leaf section. Green, tan, and with an irregular outline of peaks and valleys, this caterpillar easily hides in plain sight against a September oak leaf.
The wavy-lined prominent is a perfect match for its preferred host plant, hickory. A struggling hickory leaf scars deep brown to black and is often invaded by lines of white mildew. Earlier stages of this species are also adorned with branching antlers, perhaps used to battle the tiny parasitoid wasps and flies that plague them.
The double-toothed prominent exactly matches it's sole host plant elm with its unique saw-toothed profile. After removing a section of leaf, the caterpillar is able to position itself to fill the space. In this way both the caterpillar and any evidence of active feeding are hidden from predators.
The white-blotched prominent is a large, fat caterpillar, but it is no less expertly camouflaged than its relatives. From a single batch of eggs, individuals of this species can develop to be bright green, dull gray, deep red, or even neon orange. Always present on top of these base colors are a splattering of gall, fungus, and burn scar markings. I tend to find green caterpillars early in the year or during a particularly wet season, and red and orange caterpillars late in the fall, or during a particularly dry season. Whether they develop differently based on conditions, or whether predators gobble up any poorly camouflaged caterpillars before I can find them, is hard to say.
The aged textures and colors of summer and fall foliage are easy to take for granted. When looking at a forest as a whole, the intricate patterns and imperfections of each leaf all but dissolve against the mass of green. But for a caterpillar, a single leaf edge may serve as their primary relevant habitat, and through observing their evolved camouflage, we can gain a new appreciation for the diversity of our forests.
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