Invertebrates
Regal Moth
Citheronia regalis · also called royal walnut moth
A hiker spots what looks like a small, spiny green monster clinging to a hickory branch, and after a startled step back, realises the hickory horned devil is doing exactly what it evolved to do, bluffing its way through a life it has no real means of defending physically.
Overview
The regal moth, Citheronia regalis, is a large silk moth native to deciduous forest habitat containing hickory and walnut trees across a broad range of the eastern United States. Its enormous, intimidating hickory horned devil caterpillar and adult inability to feed at all make it one of the more visually striking and biologically compressed large moths in North America.
A bluff big enough to fool almost anyone
Every spike on a hickory horned devil caterpillar exists purely for show, an elaborate visual threat backed by absolutely no capacity to sting or bite, proving that looking dangerous can be just as effective as actually being dangerous.
Status
Least Concern, though decreasing in parts of its range — present across suitable deciduous forest habitat in the eastern United States, with declines noted particularly in the Northeast.
Regal Moth: common questions
Is the hickory horned devil caterpillar dangerous?
No, despite its intimidating, spiny appearance, the hickory horned devil caterpillar of the regal moth is completely harmless, unable to sting or bite, and relies entirely on its fearsome look to bluff potential predators into leaving it alone rather than on any actual physical defence.
How does a regal moth caterpillar pupate?
A regal moth caterpillar burrows into the soil to pupate rather than spinning a silk cocoon above ground, a pupation strategy shared with several other large silk moth relatives, spending the pupal stage hidden underground before emerging as an adult moth.
Why has the regal moth declined in parts of its range?
Regal moth populations have declined in parts of the eastern United States, particularly in the Northeast, likely due to a combination of habitat loss and other pressures affecting the hickory and walnut forest the species depends on, prompting monitoring efforts in some states despite the species remaining Least Concern overall.
Does the adult regal moth eat anything?
No, an adult regal moth has no functional mouthparts and cannot feed at all, instead surviving for roughly a week or two purely on fat reserves built up during its caterpillar stage, using that limited time solely to find a mate before dying.