Sac-spiders
Guides
Castianeira
Ant-mimic Sac Spiders, Ant-mimic Spiders
Castianeira is a genus of ant-mimicking sac spiders in the family Corinnidae, first described by Eugen von Keyserling in 1879. The genus contains approximately 127 species 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.
Cheiracanthiidae
Long-legged Sac Spiders
Cheiracanthiidae is a family of araneomorph spiders established by Wagner in 1887, with priority over the synonym Eutichuridae. The family contains approximately 15 genera and 385 species as of 2026, with Cheiracanthium being the largest and most species-rich genus. Members are commonly known as long-legged sac spiders. The family's phylogenetic placement has been historically contested, having been assigned to Clubionidae, Miturgidae, and Eutichuridae before recognition as a distinct family. Molecular analyses indicate Cheiracanthium is paraphyletic, with divergence estimated at 67 million years ago.
Corinnidae
corinnid sac spiders, ground and ant-mimic sac spiders
Corinnidae is a family of araneomorph spiders comprising over 800 species in 71+ genera worldwide. Formerly part of the catch-all family Clubionidae, the group was redefined in 2014 to include only subfamilies Corinninae and Castianeirinae. Members are wandering predators that construct silken sac retreats, with many genera exhibiting ant-mimicry as a defensive strategy. The family includes notable ant-mimicking genera such as Castianeira, Myrmecotypus, Mazax, and Myrmecium.
Liocranidae
sac spiders
Liocranidae is a family of araneomorph spiders first described by Eugène Simon in 1897. They are commonly referred to as 'sac spiders' due to their habit of constructing silk retreats. The family contains 35 genera and approximately 357 species as of January 2026. The holarctic genus Agroeca is the best-known member, while many other genera remain poorly studied and lack formal diagnoses. Recent taxonomic work has significantly expanded the family, including the description of numerous new species from China, Vietnam, and other regions.
Miturgidae
Prowling Spiders
Miturgidae is a family of araneomorph spiders commonly known as prowling spiders. The family includes approximately 160-200 species across 33 genera worldwide. Members are small to medium-sized, active hunters that do not construct permanent webs for prey capture. The family has undergone substantial taxonomic revision, with the former family Zoridae synonymized and the genus Cheiracanthium (longlegged sac spiders) transferred to the separate family Cheiracanthiidae.
Xeropigo
Xeropigo is a genus of sac spiders in the family Corinnidae, first described by O. Pickard-Cambridge in 1882. The genus comprises 17 described species distributed across South America and the Caribbean, with the majority of species occurring in Brazil. Recent taxonomic revisions have significantly expanded the known diversity, with seven new species described from Brazil in 2016. The genus shows notable species richness in northeastern Brazilian states, particularly Piauí, Ceará, and Maranhão.