I found this and want to catch it, but I get an error when I try to use my traps. What do I do?

The Luminescent Lunemara is what is called a "Named"- or a Boss, basically.
She cannot be caught by the player, the same way other Named pets can't be caught.
Named sylesti opponents almost always have an NPC owner- such as, say Bolt and Thunder, Lord Talon's vulnyxes (Hence capturing them would be... sylestinapping?)

Aww... what if I want to kidnap them anyway? ;w;

Thanks for the help!