Nice, I was hoping for butterflies. Moths are just as cool! (Assuming that is indeed the case.) There were some other eggs which looked like they had already hatched, and those looked darker.
I thought it was interesting. I wonder if they lay eggs like this on native Opuntia spines too, or if the height of Trichocereus makes them more suitable.
The eggs look a bit old - nearby spider webs swept over them and such - so I don't think they hatched too recently... but that's a good idea, I'll see if I can spot anyone left hanging around. Will be checking them every day now anyway, so I'll see the next batch for sure