Butterflies Myth

Grandma told me not to kill the butterfly which flews into our house. They are the spirits of our ancestors. Is it true?

I found some websites stating:

--"According to Native North American legend, the caterpillar transforms into the butterfly to teach us that all life is transitory. The Butterflies are ancestor spirits. Before they leave this Earth, they are permitted one last time, to return to the places of ceremony and celebration, the sacred places where as humans they experienced great joy"

--" butterfly is symbolic of rebirth after death.

This one had been sticking on my room wall for more than 24 hrs...Is that grandma? Why not it transform into a real person instead :(

~Fly Butterfly~