BAD IDEA
Can I have a pet butterfly to find out if they sleep?
You can try, but a pet butterfly won't answer if they sleep — and it probably won't survive your place long.
Butterflies are delicate little creatures not meant for pet life, and keeping one to spy on its sleep habits is as practical as herding cats — but cats that fly. They don’t have eyelids and their 'sleep' is more like rest periods, so observing them won't be straightforward. Plus, your butterfly will likely survive longer in the wild than in a jar.