Anuroctonus phaiodactylus

Distinguished from similar scorpions by the presence of an enlarged, bulbous swelling on the telson (stinger segment). This feature is the basis for the common name California swollen stinger scorpion. Under UV light, the fluorescent exoskeleton aids in detection. Differentiation from other Anuroctonus species requires examination of pedipalp and metasomal segment morphology.

Medium-sized scorpion with a distinctive enlarged bulb or swelling on the telson (terminal segment bearing the stinger). The body is divided into the cephalothorax and abdomen, with eight walking legs and large pedipalps (pincers). Like all scorpions, the exoskeleton fluoresces bright blue to green under ultraviolet light.

Found in ground-level habitats including under stones, logs, boards, and in cracks and holes in the ground. Occurs in milder regions of California including the Sierra foothills and coastal mountains. New housing developments may encounter this species when encroaching on natural habitat.

Native to western North America, with confirmed presence in California including the Sierra foothills and coastal mountains. Distribution records indicate presence in North America and Middle America.

Nocturnally active year-round in suitable conditions; diurnal retreat to shelters during daylight hours. Specific seasonal activity patterns not documented.

Preys on ground-dwelling insects and other small animals. In captivity, has been observed to attack and consume crickets and cockroaches immediately upon presentation.

Live-bearing (viviparous); females produce 20-30 live young at a time. Young are carried on the female's back for the first 5-15 days of life. Adults generally live two to three years and do not begin reproducing until nearly one year old.

Nocturnal predator. Exhibits aggressive behavior: stinging prey immediately upon encounter and attacking water when poured into enclosure. Hides under cover during daylight hours. Prey capture involves rapid stinging response.

Predator of ground-dwelling arthropods and small invertebrates. May serve as prey for larger vertebrates. Population persistence limited by availability of suitable shelter and prey base.

Poses no more threat to humans than ordinary bees and wasps. Sting venom not considered medically significant for most individuals. Occasionally enters homes in new housing developments that encroach on natural habitat, but populations typically disappear within several years due to habitat loss. Used in educational outreach and research settings.

• Anuroctonus pocockiClosely related congeneric species with similar swollen telson morphology; distinguished by subtle differences in pedipalp and metasomal segment characteristics
• Other California scorpion species (e.g., Paruroctonus, Hadrurus)Lack the distinctive enlarged bulb on the telson; Hadrurus species are significantly larger (up to 6 inches)

• BugGuide
• GBIF taxonomy match
• NCBI Taxonomy
• Catalogue of Life
• Meet Awesome Annie, the Scorpion, at UC Davis Biodiversity Museum Day | Bug Squad