Egg

Butterfly eggs have an appearance that is different from any other egg that you may find.  See the picture below.  They can have many different colors such as green, yellow, brown, white, red, or even blue.  The eggs vary in size.  "Some eggs are round like balls, where other eggs take on many different shapes such as barrels, pancakes, or pickles. Usually their shells are covered with lines and dots that cannot be seen to the naked eye, but with a microscope or telescope it can be seen." The mother  has a natural glue that is used so that the egg will stay put on the leaf and not fall on the ground. The buttlerflies can lay one egg on the leaf or possible hundreds.

Resource: http://www.uoregon.edu/~rarditi/page1/butterfly.htm