Castianeira

Keyserling, 1879

Ant-mimic Sac Spiders, Ant-mimic Spiders

Species Guides

16

Castianeira is a of -mimicking sac spiders in the Corinnidae, first described by Eugen von Keyserling in 1879. The genus contains approximately 127 distributed across Eurasia, Africa, and the Americas, with notable diversity in North America (26 species) and Mexico/Central America. These spiders are recognized for their remarkable ant-mimicry, achieved through body shape, coloration, and behavioral adaptations.

Castianeira trilineata by (c) Gordon C. Snelling, some rights reserved (CC BY), uploaded by Gordon C. Snelling. Used under a CC-BY license.Castianeira crucigera by (c) Luke, some rights reserved (CC BY), uploaded by Luke. Used under a CC-BY license.Castianeira crucigera by no rights reserved, uploaded by Lyn Roueche. Used under a CC0 license.

Pronunciation

How to pronounce Castianeira: //ˌkæstəˈnaɪərə//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from similar -mimic spiders in the Micaria by having two procurved rows of eight (upper row slightly wider than lower), whereas Micaria almost always have straight eye rows. The opisthosoma is elongate to oval, not constricted, with white -like setae contributing to ant-like appearance. Rear legs are longest, front legs second longest. Some species display pale bands on the that create the illusion of three body segments.

Images

Habitat

Woodland , particularly forest floor leaf litter. Rocky habitats in montane regions. Found in oak-hickory forests, glades, and areas with decaying logs and rock crevices.

Distribution

Eurasia, Africa, and the Americas. Absent from Australia. In North America: northeastern U.S. and adjacent southern Canada, west to South Dakota, south to Arkansas and Florida. Also documented in the northern Rocky Mountains (Wyoming, USA), Colorado, and Vermont.

Seasonality

Active both day and night during warmer months. Can overwinter in dense silken sacks spun in sheltered situations such as rock crevices and recesses of decaying logs.

Diet

Insect prey. Some are known to prey on ants, including fire ants in Texas.

Behavior

Exhibits -mimicry including slow, deliberate movement while prowling, abdominal bobbing, and waving front legs like . Some appear in the company of ants to reinforce their disguise. Mating behavior has been observed and described for the first time in the field in Wyoming, USA.

Ecological Role

. Some function as specialized predators, using mimicry to approach prey.

Human Relevance

Not recognized as dangerously venomous to people. Occasionally encountered in domestic settings such as on doorknobs.

Similar Taxa

  • MicariaSimilar -mimic sac spiders, but distinguished by straight rows versus procurved rows in Castianeira.
  • MyrmekaphilaOther -mimicking spiders; Castianeira may be distinguished by specific ant species mimicked and arrangement.

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Sources and further reading