See Observations

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