I have studied insects and spiders for many years, yet the first time I came upon this caterpillar had to be one of my most memorable insect encounters. Without a doubt, the fully grown caterpillar of the Royal Walnut Moth is a creature you will never forget. When I was a young adult, my father and I were walking down his road when he reached down and picked up a writhing creature. “Look, he smiled, “ a Hickory Horned Devil!” I had seen pictures of this caterpillar and seen the adult moth, but had never seen the huge caterpillar in the wild. It was about 5 inches long, with an aqua body, huge black and reddish brown horns around its head, and smaller prickly horns along its body segments. My father assured me that it didn’t sting, that the “horns” were largely a protection against predators, and warned me that I would be surprised at how heavy it was. He was right on all counts.
When I picked up the caterpillar, it curled into a ball, but soon began to crawl up my arm. I did feel a slight prickle on my arm, but easily put it in a cup I was carrying in order to observe it later at home. The next day, I offered it to the local Nature Center , who gladly accepted the unusual guest.
It was many years before my next encounter. My teenaged daughter found an adult female beneath a street light on a busy street. It was unable to fly, so she put it in a container and brought it to me. We feared she was dead, but left her in the container inside our house. The next afternoon when we checked on her, she had surprised us with over 30 yellow eggs about the size on a lower case “o” on a twelve point typeset.
The moth, itself is large and quite beautiful. The female can have a wingspan of 4-6 inches. She has an orange body, about an inch and a half (or more) in length. Her wings have yellow markings on a grey background. The wings are lined with orange veins. Many of the adult females have pinkish tint to areas of their wings. They look like no other moth and because of their size and color are easy to identify, She is fuzzy and when disturbed, will flap her wings wildly, in order to escape. Because she is so heavy, she doesn’t fly a long distance and will calm down if confined to a box or container.
We did some research on the moth and found out their adult lifespan is very short. They do not feed at all. They are born one evening, mate the next, with the female laying her eggs on the leaves of the host plant the next evening. Exhausted, both male and female soon die. Resources such as the Golden Guide and the National Audubon Society Guide list their preferred natal plants as hickory, sweet gum, walnut, ash, sumac and persimmon. Because the female lays her eggs on the leaves of large trees, we don’t often see the caterpillars until they come down to form into cocoons, made of leaves and silk. There they lie, under the cover of leaves until they hatch the next spring. Likewise, with a three day life as an adult, chances of seeing them are small.
As amateur naturalists, my children and I decided to raise the caterpillars and see if we could watch them through their life cycle. We gathered walnut and persimmon leaves and scattered them in a cardboard box covered with screen. In about six days, the eggs began to hatch. The tiny caterpillars appeared black at first, but after several molts, the looked more like bird droppings, with black and white markings. This was obviously to deter predation. As they continue to grow, they become more colorful and start to develop the classic “horns” which give them their nick name. I enjoyed picking them up, observing their weight and features as they grew. The “horns” are, indeed, ominous looking, but they have no sting and do not bite.
The caterpillars became so large that the box was crowded with the huge hungry creatures. We decided to release some onto their natal plants in order to have more room and in hopes that a natural environment would be more likely to produce adults the next season. After a few weeks of voracious feeding and amazing growth, the caterpillars stopped eating, appeared to shrunk in size and soon began their transformation into cocoons.
Unfortunately, many of our caterpillars died before they turned into cocoons. The few that did pupate, we kept in an aquarium in the basement over the winter, trying to add a bit of moisture and light. Unfortunately, none of the ones we kept survived to hatch the next spring.
It has been over ten years since our first attempt to raise the “Hickory Horned Devil” caterpillars. Today, my teen son, who was three years old the last time we raised them, found an adult female at a gas station and brought her home. Whether she has laid her eggs or mated is yet to be seen. She is quite active, living as her predecessor did, in a cardboard box with a screen covering it. We enjoy any opportunity to watch the life cycle of any insect we find. Perhaps we will get another chance to observe the life cycle of this huge, beautiful but rarely seen moth..