Garden tiger moth

Arctia caja belongs to the tiger-moth subfamily Arctiinae within Erebidae. Its caterpillar is one of the densely hairy larvae commonly called woolly bears. [2][1]

The forewings carry irregular brown patches separated by cream-white channels. Orange hindwings bear rounded blue-black spots. The relative area and arrangement of these markings vary between individuals; the two sides of one moth can also differ. [1]

The species has a Holarctic distribution, extending across Europe and temperate Asia to Japan. In North America it occurs in the northern boreal belt and western mountain regions. [2]

The caterpillar overwinters in low vegetation and later pupates in a silken web near the ground. European accounts describe a predominantly single annual generation, with nocturnal adults flying in summer. [2]

Adults do not feed. The energy available for flight and reproduction is accumulated during larval growth, a reproductive strategy termed capital breeding. [3]

When disturbed, an adult can expose its brightly patterned hindwings and release yellow fluid from behind the head. These are distinct components of its defensive display. [1]

In a split-brood rearing experiment published in 2025, offspring of wild-caught females experienced either brighter artificial night lighting or a dim control treatment. Larval mortality increased under brighter lighting in both generations. Female pupal mass was lower in both generations; male pupal mass was higher in the first and unchanged in the second. [3]