Xystocheir dissecta taibona

As a subspecies of X. dissecta, it would share the general characteristics of the species: a flat-backed body form typical of Polydesmida, with paranota (lateral extensions of the body segments). Specific diagnostic features distinguishing taibona from the nominate subspecies are not documented in available sources. The subspecies was described by Chamberlin in 1912, but current taxonomic treatment considers it a synonym of Xystocheir taibona.

Oak woodlands of the San Francisco Bay Area, based on collection records of the species and observations of its predator Promecognathus.

California, United States. The range is restricted to the San Francisco Bay Area and surrounding regions, based on distribution records and studies of its predator-prey relationship with Promecognathus beetles.

Activity peaks in late winter to early spring, correlated with moisture availability from winter rains. At higher elevations and northern parts of the range, activity extends into late spring and early summer. During dry periods, the millipedes are difficult to locate.

Detritivore; feeds on decaying plant material in forest floor habitats.

When attacked, individuals twist violently and curl into a tight ball to shield the ventral surface. They deploy chemical defenses from glands along the sides of each body segment, releasing hydrogen cyanide gas and benzaldehyde. The cyanide emission can be produced in profuse amounts sufficient to cause eye irritation and headaches in human observers at close range.

Serves as a specialized food source for the cyanide-tolerant carabid beetle Promecognathus. The predator-prey relationship represents a unique ecological interaction involving chemical defense and tolerance rather than avoidance.

• Xystocheir dissecta dissectaNominate subspecies of the same species; taibona was described as a distinct subspecies based on geographic separation in California but is now treated as a synonym of Xystocheir taibona
• Other PolydesmidaMany flat-backed millipedes share the cyanide defense mechanism, but Xystocheir species are distinguished by their specific association with Promecognathus predators and their restricted Bay Area distribution

• millipede
• cyanide
• chemical defense
• Polydesmida
• Xystodesmidae
• California endemic
• Promecognathus prey
• oak woodland
• detritivore
• synonym

• BugGuide
• GBIF taxonomy match
• Catalogue of Life
• These Beetles Withstand Cyanide Blasts to Eat Millipedes
• Halictidae | Beetles In The Bush