One of the most frequently seen butterflies in midwinter at low elevation, and often very common in the urban Bay Area, the Red Admiral occurs all around the Northern Hemisphere. It is multiple-brooded, overwinters as an adult, and may undergo altitudinal migration in the Sierra (where it is generally uncommon). Males are territorial in late afternoon in sites open to the W or SW, I.e. to the lowering sun. They often share these sites with West Coast Ladies and (when present) Painted Ladies, and sometimes other Nymphalids as well. Both within- and between-species chases are common. The Red Admiral and West Coast Lady hybridize, but very rarely. The hybrid phenotype is called edwardsi and is more frequently encountered in the South State for some reason.
The larval hosts are all members of the Nettle family, Urticaceae, including not only the familiar Stinging Nettles (Urtica holosericea and U. urens) but the tiny-leaved ground cover Baby's Tears (Helxine or Soleirolia) in moist, shaded gardens and the climbing urban weed Pellitory (Parietaria) in the Bay Area. The larva is solitary, in a rolled-leaf shelter.