What are the similarities and differences between crabs and butterflies?

crab 1. eyes of the crab are quite small.

2. they enable the crab to look all around.

3. the crab can sense even if the enemy approaches from behind.

butterflies 1. butterflies has a large eyes that seem to be made up of thousand of littel eyes.

2. they can see not only in the front and the sides but back as well.