Nature: Hot dog! The hickory horned devil is one giant caterpillar!

A hickory horned devil in a hotdog bun for scale/Jim McCormac

Nature: Hot dog! The hickory horned devil is one giant caterpillar!

Columbus Dispatch
September 18, 2022

NATURE
Jim McCormac

A hidden army reaches a crescendo about this time of year. Its tubular soldiers are largely out of sight and mind, but wage battle with vegetation on an epic scale. Mostly emerging under cover of darkness — the better to avoid threats like hungry songbirds — caterpillars play an enormous but largely unsung role in ecology.

The ranks of caterpillars include scores of spectacular creatures, some seemingly lifted from the works of Dr. Seuss, or Alice in Wonderland. Accompanying this column is a photo of eastern North America’s largest species, the hickory horned devil (Citheronia regalis). It is often likened to a hot dog as a size scale, which is why I placed one in a bun for the photo. The horned devil was released unharmed on a black walnut (a common host plant).

If all goes well for the devil, it will eventually morph into a regal moth, a bat-sized behemoth clad in cinnamon scales punctuated with cream-colored spots. So different are the larva and adult moth that they go by different common names. Such bifurcated nomenclature is not uncommon in the world of moth caterpillars.

Although butterflies are far better known in the Lepidopteran world, it is moths that rule. About 140 species of butterflies have been found in Ohio. Moths crush them in diversity, with at least 2,000 documented species and scores more awaiting discovery. Both butterflies and moths have a four-part life cycle: egg, larva (caterpillar), cocoon (moth) or chrysalis (butterfly), and winged adult.

The caterpillar phase is perhaps the most interesting. Virtually all of our “cats” eat vegetation, and more often than not, a species is tied to a small group of flora, or even one plant. Native plants drive the caterpillar train. Our cats have no co-evolutionary history with nonnative invasive plants and mostly shun them.

Caterpillars are the frontline agents that transform plant tissue into nutritious protein that’s easily assimilated by other animals. They are steaks on legs, preyed upon at epic levels by all manner of predators. In response, moths, especially, engage in carpet-bombing reproduction. Females of some species might lay hundreds of eggs. This is necessary to get some offspring through the predatorial gauntlet and to the reproductive stage.

A highly conspicuous caterpillar consumer group is birds, mostly our songbirds. Without caterpillars to fuel them, many species would quickly vanish. Forests would literally fall silent. The melodies of orioles, tanagers, warblers and others would disappear. Perhaps kings of the caterpillar-eaters are the vireos. Our most common species is the red-eyed vireo, which winters in South America and temporarily occupies eastern North America to exploit the seasonal bounty of caterpillars. About one million red-eyed vireos summer in Ohio, and collectively they eat some 30 million caterpillars daily.

At the recent Mothapalooza sponsored by the Arc of Appalachia, we were fortunate to have the Caterpillar Lab on hand. Founder Sam Jaffe began doing educational programs on caterpillars in 2008, and in 2015 launched the lab, which is based in New Hampshire.

Jaffe and crew enjoy visiting Ohio and have been here numerous times, including several Mothapaloozas. They bring many fascinating specimens and entrance audiences with wee beasts that are all around, but rarely seen. The lab directly contacts about 40,000 people a year, which includes many school visits.

Jaffe and company are pied pipers for caterpillar conservation, and by extension, overall preservation of biodiversity. In addition to educational outreach, the lab does a variety of research, such as the effect of the loss of ash trees on caterpillar species due to the emerald ash borer.

We hope to have the Caterpillar Lab back in Ohio for the next Mothapalooza, which will be July 14-16, 2023, at the Highlands Nature Sanctuary. It’s an event probably quite unlike any other you’ve experienced, and attendees will see legions of interesting moths and caterpillars. Mothapalooza fills quickly, so watch the website for details. Registration will open sometime next spring: https://arcofappalachia.org/Mothapalooza

Naturalist Jim McCormac writes a column for The Dispatch on the first, third and fifth Sundays of the month. He also writes about nature at www.jimmccormac.blogspot.com.