Polyphemus Caterpillars Ecdyse into Second Instar

Our oldest first instar Polyphemus caterpillars (Antheraea polyphemus) have ecdysed into second instar.

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As expected, many of our Polyphemus caterpillars (that entered apolysis yesterday) began ecdysing into second instar beginning at around 2:00 PM this afternoon. We caught the third just as it was starting to do it and took some photos as seen below. 

Unlike many caterpillars that have a dramatic change from first to second instar like the Cecropia caterpillars, the Polyphemus second instars don't look much different than the first instar ones, but there are a few changes. First, the two black lines on each segment that run along the side of the base of the tubercles are completely gone now, but there seems to be a faint line in the middle of the segments that bisects the spiracle instead. The spiracles are also surrounded by a brownish red ring now as well. In addition, the body color is now much more vibrantly green and the tubercles are larger and brighter yellow. They carry the same number of hairs on top as first instar, with eight on the four large dorsal ones on T2 and T3 and a ring of five on most of the others. Interestingly, these are the same numbers as the Cecropia and Ceanothus second instar caterpillars, and the three species look remarkably similar in shape in this instar. The Polyphemus tubercles look nearly the exact same as the Hyalophoras at this age and probably many other Saturniids that we haven't reared, but they will eventually be reduced increasingly smaller as they age, while the Hyalophoras will become larger and more developed. When the caterpillars first molted, their head capsules were pale green as seen above, but eventually they became a coffee brown which differs from the more reddish, burgundy brown in first instar, though the shade seems to be slightly different between each caterpillar, but we can't say for sue until they've all fully tanned. 

These Polyphemus caterpillar growth rates seem to be on par with the other Saturniids we have raised, taking about 7 days and 2 hours from 7/15-7/22. So far they haven't diverged in age very much; most seem within a day apart of each other which is expected since most hatched within a day of each other. However, two caterpillars in the youngest dish, one of which was the late hatcher on 7/17 look very weak for some reason, though it is definitely not disease. 

Anyway, here is the count for today: L2: 13; L1+: 17; L1: 7; dead: 1 (died shortly after birth).

- Alan