I was hiking through the Ouachita National Forest in Arkansas early one October morning when something bright caught my eye. Crawling along a low branch near a hickory tree was a creature that looked straight out of science fiction. It had long, curved black and red horns and a thick green body covered in spines. I had no idea what I was looking at, but I knew I needed to photograph it.
When I got home and did some research, I learned this was a Hickory Horned Devil, the caterpillar stage of the Regal Moth (Citheronia regalis). The name fits perfectly. It’s one of the largest and most striking caterpillars in North America, and seeing one in person is unforgettable.
Wildlife Notes
The Hickory Horned Devil is the larval form of the Regal Moth, also called the Royal Walnut Moth. Fully grown, it can reach six inches long, about the size of a large hot dog. Despite its fierce appearance, it’s completely harmless. The horns and spines are for show, not defense. They don’t sting or puncture skin. The look is pure bluff meant to scare predators.
These caterpillars feed on hickory and pecan leaves, and sometimes walnut, sweet gum, persimmon, or sumac. They eat heavily through summer and early fall before crawling down to burrow into the soil. There, they spend the winter as pupae and emerge the next summer as the beautiful Regal Moth, which has a wingspan of about six inches.
Finding a Hickory Horned Devil in the wild is a lucky moment. They’re solitary and only remain caterpillars for about five weeks before heading underground. They play a role in forest health by pruning foliage and providing food for birds and small mammals. Even underground, their tunneling helps aerate soil.
Photography Notes
This shot was handheld with my Canon EOS R7 and Canon RF 100–500mm F4.5–7.1 L IS USM lens at 500mm. The caterpillar was about five feet above the ground on a thin branch.
Camera Settings:
Focal Length: 500mm
Aperture: f/8
Shutter Speed: 1/800 second
ISO: 1000
Exposure Compensation: -4/3
At 500mm, depth of field is razor thin. f/8 was just enough to keep the entire caterpillar sharp from horn tips to tail. I used 1/800 second to stop minor movement from the caterpillar and my own hand shake. The R7’s 1.6x crop factor gives an approximate 800mm field of view, which is great for wildlife reach but also magnifies vibration, so image stabilization was essential.
The bright green color tempted the camera’s meter to overexpose, so I dialed back exposure by 1⅓ stops. That preserved texture in the caterpillar’s body while keeping the background soft and unobtrusive.
Soft, overcast light made this photo possible. Harsh sunlight would have blown out highlights and caused glare on the caterpillar’s smooth skin. The diffused light revealed every ridge and color shift beautifully.
Closing Thoughts
Encounters like this remind me why I carry my camera everywhere. The Hickory Horned Devil may look like a tiny monster, but it is a harmless and essential part of the forest cycle.