See Observations

1. Oak Fern (genus: Gymnocarpium)
2. --- Oak Wilt ( Ceratocystis fagacearum)
3. --- Oakleaf Mountain Ash ( Sorbus hybrida)
4. --- Oakmoss ( Evernia prunastri)
5. --- Oblique-lined Tiger Beetle ( Cicindela tranquebarica)
6. --- Olive Angle Shades ( Phlogophora iris)
7. One-eyed Sphinx ( Smerinthus cerisyi)
8. --- One-flowered Wintergreen ( Moneses uniflora)
9. One-sided Wintergreen ( Orthilia secunda)
10. Orange Jelly Spot ( Dacrymyces chrysospermus)
11. Orange-and-Black Ichneumon Wasp (genus: Therion)
12. Orange-spotted Drone Fly ( Eristalis anthophorina)
13. --- Oriental Bittersweet ( Celastrus orbiculatus)
14. Osprey ( Pandion haliaetus)
15. Ostrich Fern ( Matteuccia struthiopteris)
16. --- Ovenbird ( Seiurus aurocapilla)
17. --- Owl-eyed Bird Dropping Moth ( Cerma cora)