Black Swallowtail Caterpillar

Description:

When provoked, the larvae of this species sprout eversible orange horns called osmeterium, which release a foul odor in order to deter predators. The osmeterium is a defensive, glandular organ that is coated in stinky chemicals, and is located at the base of the caterpillar's head (see photo 4 for slit that osmeterium pops out of). The osmeterial odor changes between species and within the life stages of the caterpillars. This particular caterpillar's osmeterium smelled like rancid citrus. The larvae of this species changes color quite dramatically with each molt. This caterpillar was mostly black with white stripes and yellow dots.

Habitat:

I spotted this caterpillar on fennel (Foeniculum vulgare) in a rural garden.

Notes:

Spotting #1,000!