Marten Edwards knows just what to say when friends come to him and admit that they think they’ve seen an alien.
The Muhlenberg College biology professor shows them a picture of a hickory horned devil ? a neon-turquoise caterpillar that can grow to be the size of a hot dog and is crowned with menacing black-tipped red horns ? and asks, “Is this it?”
It always is.
The caterpillar is an uncommon find in Pennsylvania. But last week, a Riegelsville woman and her friend’s 11-year-old daughter found two just north of the Giving Pond in the Tinicum area of Delaware Canal State Park in Bucks County.
Nina Carlineo said she and the girl were riding their bikes when the bright color, dangerously close to her bike wheel, caught her eye.
She quickly hopped off her bike to check out the roughly 6-inch-long caterpillars.
“I felt like it was an Alice in Wonderland creature,” she said.
The caterpillars eventually transform into regal moths, which can have a wingspan of up to 6 inches.
The caterpillars spend much of their lives feeding in treetops, but this time of year they descend to the ground, burrow into soil and pupate over the winter.
The moths feed on hickory and black walnut, Edwards said. Studies suggest that the moth is uncommon in the area thanks to a parasitic fly that was introduced in 1906 to kill the invasive gypsy moth.
The parasitic fly didn’t stick to the menu and feasted on large native moths, including silkmoths, luna moths and regal moths.
Edwards said studies in 2000 pinned moth decline on the fly, but a follow-up study last year found few moth larvae are still being killed by the flies.
Michael Skvarla, the director of the insect identification lab at Penn State, said the caterpillars were common decades ago but have become scarcer. They’re not classified as endangered but are in decline, with their upper range once reaching to Massachusetts and now, seemingly, closer to northern Pennsylvania, he said.
In addition to being victimized by parasitic flies, the caterpillars have suffered from habitat destruction and deforestation.
The regal moths, which have large orange and gray wings, could also be harmed by light pollution. The moths are drawn to light, and they can get confused and become easy targets for bats.
“Rather than mating or laying eggs, they’ll fly around the lights at night and just exhaust themselves and die,” Skvarla said.
The caterpillars are harmless to humans, although their spikes are sharp, Edwards said. Skvarla recommends leaving the caterpillars where they are, unless they’re on pavement or on solid ground, in which case they can be moved to an area with loose soil they can burrow into.
Edwards does not recommend anyone keep them as pets.
“They don’t provide very good companionship, and the best thing you can do is leave them exactly where you found them because if you want these species to continue, they need to stay exactly where they are,” he said.
Morning Call reporter Michelle Merlin can be reached at 610-820-6533 or at mmerlin@mcall.com.
