Updated: Dec 13, 2017
. . . In your own backyard, as it happens, munching the foliage of native trees, shrubs and herbaceous plants. Many caterpillars eat a variety of leaves (they’re “polyphageous”!); others are limited to the leaves of one plant family or even one genus. With few exceptions, they eat only the leaves of the indigenous plants with which they’ve co-evolved. As prime beneficiaries of native plantings, caterpillars have appeared frequently in this column. But they’ve been mostly relegated to a supporting role, as an essential food source for birds--especially migrating songbirds and nestlings.
Caterpillars are indeed a key element in the food chain, but as I examined my recently planted oaks, black cherries and other natives to see what bird food they might be sustaining, I discovered a world of weird and wonderful creatures, fantastic beasts astonishingly-shaped by their mission to avoid becoming bird food, to simply eat their leaves in peace until pupation time.
Spotted Apatelodes (Apetalodes torrefacta). This caterpillar feeds on a variety of native woody plants; its presence on this herbaceous avens stem indicates that it is in
search of a place to pupate.
The most elegant caterpillar to grace my yard, the Spotted Apatelodes, perches openly, flaunting its extravagently long, silky white setae (hairs), set off by the ruby satin slippers of its prolegs (not true legs, anatomically, but similarly used for crawling and clasping). Apparently its flamboyant hairiness is enough to put birds off their lunch.
Checkered-fringe Prominent (Schizura ipomoeae), resembling the dead leaf
margin to which it clings.
Other caterpillars rely on camouflage to escape notice. The closely-related Unicorn and Checker-fringed Prominent wear leaf-green vests, but their brownish heads and the bulk of their bodies are intricately patterned to resemble the reticulate venation of a dead leaf. Add to this their humped profile and they become a curled, brown leaf edge as they graze along the margin. In my yard they partake of oak, black cherry, swamp rose, and black gum.
The tiny 1 cm-long Red-crossed Button Slug (Tortricidi pallida), lower left, mimics both the green leaf and its scarlet-bordered dark spots.
Slug caterpillars, reads my favorite guidebook “seem more fantasy than reality.”* They glide along their leafy substrate, and some, like the Spun-glass Slug (still on my to-see list), are exquisite creatures. Others are masters of camouflage: the Red-cross Button slug imitates the rusty specks mottling cherry leaves—right down to the spots’ scarlet borders.
Skiff Moth Caterpillars (Prolimacodes badia)
The Skiff Moth slug matches the green hue and venation of its leafy substrate, and--in a play for ultra-realism-- sports several brown patches, resembling the necrotic tissue that flecks green leaves. This tiny tank-like cat favors my sweet gum and black cherry trees.
Saddleback Caterpillars (Acharia stimulea): their sting is perhaps the most potent of any North American caterpillar (Wagner).
The first line of defense for the striking Saddleback slug may be its neon-green and brown-saddle pattern, which blends in with the sunlit undersides of leaves, but its most impressive defense is its bristling armament of stinging spines. Don’t touch—it packs a ferocious yellow-jacket wallop. For good measure, a close look at either end reveals scary alien-monster eyes. I’ve found this cat on oak, sycamore, hazelnut and dogwood.
Spiny Oak Slug Caterpillars (Euclea delphinii). The translucent cat in the top photo is a young one (first instar), only about 3/16" long.
The Spiny Oak Slug is a relatively mild stinger. The variable coloration of this caterpillar may render it subtle and almost translucent, or with vivid warning bands of yellow, green and red. Regardless, each individual displays a daunting perimeter of spiny appendages.
While Pokemon-Go was all the rage one summer, I happened upon a real pocket monster in my black cherry sapling: the White Furcula caterpillar. This whimsical cat perches placidly atop its only food source, the cherry leaf, and even in a stiff breeze rides the midrib like a champion surfer. Its coloration, leaf-green and rusty brown, gives it some camouflage in the dappled light among the foliage, and it packs a few spines. But the Furcula’s truly ingenious mode of defense is to separate and extend the red-tipped forks of its tail and flail them about while furiously gyrating its body. Thus the zen-like koala bear transforms into a terrifying dragon with stalked glowing eyes.
White Furculas (Furcula borealis): my personal faves.
I became quite fond of “my” trio of Furculas, and was dismayed one morning to find them gone from their customary perches on the cherry tree. Anxiously surveying the foliage, I let out a hoot of astonishment: the cherry leaves, now in late September, were turning bright yellow, spotted with flecks of brown and russet--and so, naturally, had the Furculas. Moreover, they were now all three hanging upside down like drooping leaves.
Fickle human that I am, I now think it such a pity that these caterpillars, in all their delightfully eccentric forms and behaviors, might become mere bird food. If a fraction of them do survive larva and pupa-hood-- avoiding predation by not only birds but assassin bugs, parasitic wasps and flies, etc, etc--the truly remarkable metamorphosis will occur, and these cats will change into (wait for it. . .): those modest, cryptically-colored-and-patterned moths that tend to go unnoticed by us unless we leave the porchlight on. Not uninteresting creatures, but lacking the eccentric forms they enjoyed as larvae. As adult moths, they’re likely to play their role in the food chain as well. But I hope, before they do, that they’re able to find the leaves of a native plant on which to lay the eggs of the next weird and wonderful generation.
*My favorite guidebook: David L. Wagner's Caterpillars of Eastern North America (Princeton Field Guides).
An earlier version of this column was published in my monthly (more or less) column, "The Wild Garden," Bloomington Herald-Times October 2017.