The year 2009 marked the first of what is hoped will be annual monitoring of the butterfly populations at Weir Farm National Historic Site. Two walks, taken in late June and mid-July, yielded the first ever list of species. A total of 12 species were found. Following is the list:
- Great Spangled Fritillary, Speyeria cybele
- Question Mark, Polygonia interragationis
- Wood Satyr, Megisto cymela
- Clouded Sulphur , Colias philodice
- Cabbage Butterfly, Pieris rapae
- Summer Azure, Celastrina ladon
- Tawny Edge Skipper, Polites themistocles
- Hobomok Skipper, Poanes hobomok
- Silver-spotted Skipper, Epargyreus clarus
- Tiger Swallowtail, Papilio glaucus
- Monarch, Danaus Plexippus
- Little glassy wing, Pompeius verna