Hello!
I have bred this species many times, but I haven't encountered such a problem before.
For some reason the moths couldn't get out of the pupae on their own. And when I took them out of the pupae myself, they could no longer spread their wings, some were already dead. Only a few individuals hatched successfully. Very strange...
What happened to them?
Smerinthus ocellatus pupae were kept in the same conditions and all hatched successfully.