Bye bye, butterflies

Here is the last of our beautiful little friends. Mason and Ash exercised amazing restraint, keeping their hands clenched tight so they wouldn't be tempted to poke or prod the butterflies as they slowly made their way out into the cool air of the front yard. The strangest thing happened though; we had four butterflies emerge yesterday, and two the day before- but we started with five caterpillars and had five cocoons. (I am quite certain of the numbers because Mason counted them every morning, and every night.) I was thinking it was a phenomena along the lines of two-yolks-in-one-egg, but the yolks are only chick food, not chicks, so that doesn't make sense. Two caterpillars would have had to have snuggled up in one cocoon to make two butterflies, and we only had 5 caterpillars. Maybe, the caterpillar split in half like human eggs do, to create twins. Maybe I am just extremely ignorant about basic butterfly science and I should have studied up on this before beginning this project. Maybe (and this is my personal favorite) we have witnessed a divine butterfly conception. A butterfly miracle.
In any event, the butterfly pavillion was a lot of fun (explaining that you can't keep the butterflies, not so much).
If anyone can clear up the butterfly mystery, please do!