Redwood-forest
Guides
Harpaphe haydeniana
yellow-spotted millipede, almond-scented millipede, cyanide millipede
Harpaphe haydeniana is a flat-backed millipede native to the Pacific coast of North America, recognized by its black body with yellow-tipped lateral keels. The species is notable for its chemical defense system, secreting hydrogen cyanide when threatened, which produces a characteristic almond odor. It plays a significant role in forest decomposition, particularly in redwood ecosystems. Despite its common names suggesting uniqueness, both the color pattern and cyanide defense occur in other flat-backed millipedes globally.