Butterflies: California Tortoiseshell
The California Tortoiseshell butterfly is often found in Oregon, as I came to find out. We have had a series of them land on our front gardens, which happen to be shaded by some lilac bushes that have been in our yard for more than a decade. Despite the name, the range of these insects is vast, extending north from Mexico to British Columbia and east into most western states.
These butterflies, identified by their bright orange wings with black and white patches, inhabit various habitats, including mountain slopes and meadows. Interestingly, they are known for their mass migrations and population explosions, where vast numbers of the butterflies can be seen, even making headlines in areas like Oregon’s Crater Lake. We were surrounded by a vast conflagration of these flying insects many years ago, when we visited the trails around Crater Lake National Park.
The species is also known for its clever camouflage of darker grey/brown colors, which blend in well with the landscape, as seen below.
Key Characteristics
- Appearance: Bright orange upper wings with black spots, black and white patches on the leading edge of the forewing, and a dark border. The underside is two-toned with a darker inner half and a brown outer half, often with a dark gray-blue submarginal line.
- Host Plant: The larvae feed on various species of Ceanothus (Wild Lilac), such as snowbrush.
- Life Cycle: Adults overwinter and become active in late winter to lay eggs on the young Ceanothus growth.
- Behavior: After emerging in late spring or early summer, adults may migrate north or east, sometimes creating mass gatherings.
Henry E. Hooper 