It's a tortoise beetle larva, possibly Cassida viridis.

It looks like the top one is a female and the bottom one is the male larva. The differentiating "parts" are in 3rd abdomen from the bottom so some photos with more bottom part included could help to confirm this. Males also often have bigger head capsules.

Has anyone bred Argynnis pandora, the cardinal butterfly? I saw these several times on holidays in Spain and Greece. Some of them looked huge. I was wondering, if anyone bred these?

Are you looking for a live beetle or dead specimen?