Ok...I have had this game for a while now and the butterflies seem to hate my farm. I have seen 2 and collected them both. I am on Level 16 now and would like to get this challenge out the way but they seem to be staying well away.
I have tried re-arranging my farm as suggested and leaving open spaces (which is hard to do on Level 16 as I now have so many machines/workshops).
Is there another trick?!