Hog caterpillar (left) and sphinx caterpillar (right). Photo by D. Pifer.
Last summer I was lucky to find two amazing-looking sphinx moth caterpillars. They were feeding together on a Virginia creeper vine growing up the bricks next to our back door. My wife had been asking me to remove the creeper vine before its tendrils penetrated the recently restored brick and mortar of our historic house. Having procrastinated enough, I went to remove the vine only to discover a large caterpillar had eaten off nearly all the leaves. Fully three inches long, the caterpillar had hairless skin that was a pleasing chocolate brown color. Six white dots surrounded the breathing pore on each of its segments. The spots looked as if they were painted on and got progressively larger toward the rear of the caterpillar. I recognized the caterpillar as a Pandora sphinx by these spots but was surprised by its color. Pandora caterpillars can be bright green, brick red, orange or black, but seldom brown.
Like the tomato “worm” so well known to gardeners, my caterpillar was the immature life stage of a thick bodied, narrow winged hawkmoth. A sphinx caterpillar is a natural shapeshifter. When disturbed or attacked, it tucks its head in while rearing and inflating its front end into a pose that resembles the great Egyptian sphinx. Thin skinned and totally harmless, sphinx caterpillars feed constantly and voraciously on the leaves of their host plant until they attain full size. Then they burrow into some loose soil, shed their caterpillar skin and spend several months as a pupa or resting stage, with a characteristic “jug handle” where the mouth parts of the adult moth will be.
Most sphinx caterpillars have a curved horn projecting from the rear end, which may look fearsome but is mostly ornamental. But the Pandora caterpillar has a curly tail instead. Resembling a tendril of grapevine, this strange appendage allows the young caterpillar to blend into its surroundings. As it grows larger, the young Pandora caterpillar sheds its skin and finally loses its curly tail. In its place appears a very realistic fake eye. Bright brown with a dark center, surrounded by a thin white ring, and further enhanced by a glassy transparent “lens,” the “eye” is remarkably realistic. Presumably this misplaced staring eye would startle or confuse any would-be predator.
While focusing my cell phone camera lens to take a picture of this strange insect, I spotted a second caterpillar feeding next to it. About half the size of the Pandora, it looked more like a tomato sphinx, except its sides were decorated with blue-green ocean waves with “whitecaps.” A series of pink dots marked the breathing pores on each wave, and larger pink studs formed a line down its back. The rear end of this caterpillar sported a downward curving horn, green tipped with yellow. The entire caterpillar was covered with tiny white tubercles, resembling stars. Despite the bright pastel tints, it was all but invisible among the leaves of the Virginia creeper. This was the larva of the hog sphinx, another night-flying hawkmoth.
An adult Pandora sphinx moth looks as sensational as its caterpillar. Shaped like a fighter jet with a four-and-a-half-inch wingspread, it looks like it’s wearing jungle camouflage. Broken patterns of strongly contrasting light and dark green are interspersed with dashes of dull black and pink. This wild pattern, coupled with the moth’s streamlined shape, looks as if it was created by either a military flight engineer or a fashion designer. But the insect is nearly invisible while resting among the grape and Virginia creeper vines where it typically lives. A hog sphinx moth is similar in shape, but much smaller. Its wings are modestly camouflaged in alternating bands of light and dark gray, tan and reddish brown. Its hind wings are sometimes brighter orange.
Both hog and Pandora moths appear in the late spring and visit night blooming flowers such as petunia, campion, and evening primrose. Moving back and forth in the darkness, they uncurl their long tongues and probe deep into the throats of these flowers for nectar, pollinating the flowers in the process.
Doug Pifer is an artist, naturalist, and writer. He has a Master’s Degree in Journalism from Penn State and has been an editor and art educator. His illustrations have appeared in various books and magazines and he has been a contributor to The Observer for several years. He lives with his wife and assorted animals on 5.7 acres in a historic farmhouse near Shepherdstown.By Doug Pifer