Polyphemus Moth Eggs Hatch

To our surprise, our Polyphemus Moth (Antheraea polyphemus) eggs have hatched today, just a day after we received them.

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Well, this is some very exciting yet surprising news. At noon today when we checked on the Polyphemus Moth eggs that we had just received in the mail yesterday, we were delightedly surprised to find a whole gang of newly born caterpillars crawling around their eggshells in the petri dish. We counted 21 in total, with one just making its way out of its shell, though four more hatched a few hours later making 25 hatchlings for today with 14 unhatched eggs remaining. We were extremely surprised that they hatched today because we had literally received the eggs yesterday and assumed they were freshly laid and would hatch next week. But since they hatched today, this means the eggs must have been oviposited over a week ago and we were very lucky none hatched during shipping. 

The Polyphemus caterpillar hatchlings are yellowish white with huge brown head capsules. Along the entire body are very small but hairy yellow tubercles on each segment, arranged in the same way as other Silkmoth caterpillars such as Cecropia and Luna. In addition, each body segment has two black lines that run along the sides of the bases of the tubercles.

After the caterpillars hatched, a few ate parts of their eggs shells but most didn't and wandered around the dish. Like most Saturniidae, they shouldn't actually settle down and begin feeding on foliage until around dusk, so we had some time to figure out what rearing method to use and find leaves. As discussed on yesterday's post, we wanted to try using either the native Coast Live Oak (Quercus agrifolia) which is extremely common here or the the few landscape deciduous oak species). Before we weren't quite sure what to use because agrifolia is abundant but has tough small leaves, while the red oak group of oaks are broad and smooth leaved but are very few and require us to walk quite a distance just to pick some leaves. However, when we took a walk around the city to look for oaks, we realized the live oak leaves were simply just unusable looking- they were so small, hard and prickly enough to pierce skin. Instead, we found a spot with three decently sized landscape oak trees that we later identified as scarlet oaks (Quercus coccinea) that had nice low branches for picking with pretty good condition leaves. We cut a small branch from it and headed to another location with a landscape oak tree. This oak was huge but with plenty of reachable branches that we later identified as pin oak (Quercus palustris). The leaves were broad and glossy and were in excellent condition, so we took a small branch from it as well to see which oak the Polyphemus would prefer. 

When we got home, we decided to use six large petri dishes for the 25 caterpillars, with five dishes of four and one dish of five. This is a different method from what we used for the other Saturniids we have raised where we used air tight plastic tubs, because we don't think the extra humidity is necessary; it'll just instigate disease and as long as the leaves are fresh enough the caterpillars shouldn't desiccate. We placed a pin oak leaf in four dishes and a scarlet oak leaf in the other two and stuck the petioles into a small tubes filled with water with a hole poked at the top in order to keep the leaves fresh. One of the pin oak dishes is the one dish of five caterpillars.

At night (10:00 PM) we took a brief check on the caterpillars to see if they had begun feeding and noticed that in the four pin oak dishes there were a few holes made by a few caterpillars but most of them hadn't settled down yet and were wandering all over the dish. On the other hand, every single one of the caterpillars in the two scarlet oak dishes were settled peacefully on the leaf and there were a few nibbles on the sides of the leaves. From this it appears they have a preference for the scarlet oak, so we actually took out the pin oak leaf from one of the pin oak dishes and replaced it with a scarlet oak leaf. We well see tomorrow how much feeding there will be on the leaves.

- Alan