Around the end of September, we found ourselves with a handful of Hickory Horned Devil (Citheronia regalis) caterpillars to raise. (If you missed that post, check it out here.) Although they seemed to be about full-size when we found them, they spent another couple of weeks in our lab feeding on Sweet Gum leaves and leaving behind frass the size of garden peas. At last they could eat no more, and turned a gorgeous turquoise color, indicating they were ready to begin the next stage of their life cycle.
When caterpillars of any species are ready to pupate, they first expel all extraneous material from their body, including any waste products and undigested plant material. This compresses their body size down to the bare essentials. Our Hickory Horned Devils went from the size of hotdogs (about 6 inches long) to less than half that, ending up about a couple of inches long.
This happened over a period of a day or two. Then, they simply rested on the soil we placed in their tank for about three more days. During this time, they did not eat or move around, although they would wiggle fiercely when poked. Finally, we came in one morning to find they had shed their final skin, shown below with the fearsome horns still attached.
With their final moult behind them, the Hickory Horned Devils had become pupae – a deep dark brown (almost black) little package about two inches long.
The pupa is firm and dry to the touch, but it will wiggle a bit if handled, to scare off any potential predators. Inside that little package, metamorphosis is slowly taking place, as the adult moth forms from the same genetic material that made the caterpillar. This process will happen over many months, since this species generally only breeds once each year. It will likely be eight or nine months before the Regal Moths emerge to begin the cycle over again.
We’ve bedded our pupae down for the winter in a container of soil and leaf litter, mimicking the conditions they would experience in the wild. We have them in a safe place in our lab, where we can keep an eye on them until they’re ready to emerge next year and show off their brilliant wings and giant fuzzy bodies. We can hardly wait!
Did your Regal Moth ever emerge this summmer? One of my students found one of these caterpillars (amazing creature!) yesterday, and we were debating whether to keep it and give it some soil to bed in, or let it go. Most likely we'll keep it and give it a try. Thank you for your resource here! I found it last night, and we'll be looking at in class this morning!
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