Doug Wechsler / Poison ivy vine (Toxicodendron radicans) climbing up White oak tree (Quercus) Fort Washington State Park, Pennsylvania, USA October

Doug Wechsler / Poison Ivy (Toxicodendron radicans) Schuylkill Center, Philadelphia, Pennsylvania, USA, April.

Doug Wechsler / Poison Ivy Sawfly (Arge humeralis) on goldenrod, Morris Arboretum, Philadelphia, Pennsylvania, USA, July.

Doug Wechsler / Poison Ivy (Toxicodendron radicans) climbing round tree trunk, Schuylkill Center, Philadelphia, Pennsylvania, USA, April.

Doug Wechsler / Poison Ivy (Toxicodendron radicans) on tree, Schuylkill Center, Philadelphia, Pennsylvania, USA, April.

Jeff Foott / Eastern Poison Ivy (Toxicodendron radicans) in autumn, Colorado Plateau, Utah