How are the butterflies built? In AE? From Photoshop or Illustrator files? How did you import them?
They were built in Illustrator, and imported as 3 separate layers - body, Lt wing, Rt Wing
Were these three separate documents, or did you prepare an Illustrator document in three LAYERS -- Illustrator folks tend to forget the fact that you can make layers -- and import it as a comp?
When you import an Illustrator document as a comp, you have two options. One of them takes the anchor points from the layers and one doesn't. I forget which is which.
I would have set this up in Illustrator Before you started. Start with a rectangle that has either fill or stroke on a layer but the opacity is set to 0. The center of the rectangle will be the anchor point for that layer when you import as a comp maintaining layer size. Now create your left left side contents on the left side of the rectangle and repeat for the right side. Import as a comp and you'll be golden.
Here is a sample file and what the file looks like imported as a comp. Notice the x values of all anchor points are identical.
The artwork isn't great, it was created in less than a minute but it porves the workflow.