First Two Cecropia Caterpillars Ecdyse to Fifth Instar

Our oldest two fourth instar Cecropia caterpillars (Hyalophora cecropia) have ecdysed into fifth instar.

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This morning when we checked on our Cecropia caterpillars, the fourth instar that entered apolysis on 7/6 had finally ecdysed into fifth instar after nearly four days, shown in the left and middle photos. We are not sure when it did it exactly, but based on the fact that the cuticle was mostly tanned and it has already eaten a portion of its old exocuticle, it had probably done it several hours ago during the night or early morning. When we checked on the caterpillars again in the afternoon (5-ish?), the plum eater that entered apolysis on 7/7 had just ecdysed as well, with its new cuticle still moist (right photo). Seems they were still very close in age after all since both ecdysed on the same day despite entering apolysis on different days, but the apple eater is still several hours ahead.

​There are many differences between the newly molted fifth instar caterpillar and the fourth instar caterpillars. First, the cuticle is much smoother and has a deeper turquoise green coloration than before, probably because the powdery white coating was shed off with the old cuticle, but will accumulate again in a few days. The head capsule, true legs and prolegs, spiracles, and tubercles are now huge in comparison to the body because it will grow an incredible amount during this final instar. The tubercles have changed quite a bit in size, shape, and color as well. They are at least twice the size as before, and they are much more elongated in shape, especially the abdominal ones. Many of the black spikes on the tips have been reduced into black spots, such as on the six large ones on T2, T3, and A1, or completely disappeared as seen on most of the other tubercles which only have one or two central spikes now instead of a ring of five. The tubercles colors have changes as well, with the four red ones now more of an orange red and the two large yellow ones on A1 now a yellow-orange. The blue lateral tubercles seem lighter in color now as well.

With two fifth instar caterpillars now with many fourths in apolysis, our Cecropia caterpillar journey is coming near to an end, and we hope most will survive to cocoon. This final instar should take a good two weeks and we hope we will have great fun with them in this coming time.

Anyway, here are the numbers for today: L5: 2; L4+: 9; L4: 12; L3: 1; dead: 12 (2 drowned, 10 disease)

​Finally, for the record, today is the 34th day since the first caterpillars hatched, and marks the end of fourth instar for the oldest individual, which lasted approximately 12 days and 11-21 hours from 6/27-7/10. Third instar lasted roughly 6 days and 17 hours from 6/20-6/27, second instar lasted for roughly 6 days and 1-2 hours from 6/14-6/20, and first instar lasted for roughly seven days and 6 hours from 6/7-6/14.

- Alan