The first three instars of the caterpillar are bird dropping mimics, coloration that helps protect it from predators.
In later instars, the eyespots on the thorax serve to deter birds.
Like all members of the family Papilionidae, the caterpillar of P. glaucus possesses an osmeterium, an orange, fleshy organ that emits foul-smelling terpenes to repel predators.
Normally hidden, the osmeterium is located on the first segment of the thorax, and can be everted when the caterpillar feels threatened.
The combination of eyespots and osmeterium makes the caterpillar resemble a snake.

Since adults are palatable, dark morph females use Batesian mimicry to protect themselves from vertebrate predators by mimicking the poisonous pipevine swallowtail.
Dark morph females are more prevalent in the south, where B. philenor is more common.
The first three instars of the caterpillar are bird dropping mimics, coloration that helps protect it from predators. In later instars, the eyespots on the thorax serve to deter birds. Like all members of the family Papilionidae, the caterpillar of P. glaucus possesses an osmeterium, an orange, fleshy organ that emits foul-smelling terpenes to repel predators. Normally hidden, the osmeterium is located on the first segment of the thorax, and can be everted when the caterpillar feels threatened. The combination of eyespots and osmeterium makes the caterpillar resemble a snake.
Since adults are palatable, dark morph females use Batesian mimicry to protect themselves from vertebrate predators by mimicking the poisonous pipevine swallowtail. Dark morph females are more prevalent in the south, where B. philenor is more common.
Papilio glaucus