From the first time I saw pictures of the larvae of the Royal Walnut Moth (Citheronia regalis) I had wanted to try raising some of these spectacular caterpillars. This summer I finally had the opportunity. The year before I had purchased pupae from a breeder, but the female failed to attract a mate, and the male of the purchased pair never emerged from the pupa. This year, both male and female emerged on the same day.
The details of their mating were somewhat amusing, so I’ll share those here. I put the pair together in a large cage, expecting them to mate during the night. Instead, they immediately moved apart, and were on opposite sides of the cage in the morning. As I had read that siblings were sometimes reluctant to breed, I decided that this could be the problem. However, I decided to try putting them in the small breeding cage and moving it to a more open area in hope of attracting a wild male. The breeding cage is a wire mesh cylinder open at the top, so I placed each moth in from the top. However, I accidentally dropped the much heavier female in on top of the little male. When she landed on him, he threw both wings up over his back and just sat there, quivering all over. Rather than interfering, I just left them to straighten things out and covered the cage. Well, the next A.M. I found they had mated. Guess he liked his ladies rough!
They remained attached most of the next day, and then she immediately began to lay eggs. These moths lay translucent yellow eggs, through which the larvae can be seen as they develop. I was not able to see them clearly until a few days before hatching, but at about 7 to 9 days the head darkens, and a striping of brown on the body can be seen.. Since I had kept only the eggs from one day’s laying, hatching was rapid once it began. These fellows can grow to 6 inches long, and I only had space enough to raise a limited number if they were not to be over crowded. Crowding of any living thing is a sure recipe for disastrous results.
As recommended by the breeder from whom I had obtained the parents, I separated the tiny hatchlings four to a quart size plactic container and offered pieces of black walnut leaves. Within a fairly short time they had outgrown the little tubs and were moved into larger quarters. The contrast between their growth and that of the Luna caterpillars I was also raising was striking. The fearsome appearance of these caterpillars has earned them the common name of “Hickory Horned Devils”, and you can imagine the comments I got when taking them to speaking engagements. Mine finally reached 5″ to a maximum of 5 1/2 ” in length. When ready to pupate they changed from green to blue and began to wander away from their food. I provided the plastic tubs with paper towels for them to burrow into and shed that final caterpillar skin in exchange for the brown pupal shell, in which they will spend the winter safely tucked away in my spare refrigerator until next spring. Most of my 36 pupa were carefully wrapped and shipped back to the breeder from whom I had obtained the parents. I did keep a few for myself, though, in hope of having the opportunity to again witness this wonder of nature’s cycle.