Xysticus

Xysticus is a genus of around 300 ground crab spider species described by C. L. Koch in 1835, belonging to the order Araneae, family Thomisidae.

The genus name is derived from the Ancient Greek root xyst, meaning "scraped, scraper".

The spiders of the genus Xysticus do not build webs; like most Thomisidae they are ambush hunters and prefer to hunt near the ground (hence the common name "ground crab spiders"). They move slowly, and commonly hunt by stationing themselves in a high-traffic area and grabbing whatever arthropod passes close enough. Also like most other Thomisidae, they seize prey with their enlarged anterior two pairs of legs and kill it by a venomous bite.

Xysticus and Coriarachne are dark brown or reddish-brown crab spiders often encountered on weeds or trees. While similar to the 'flower spiders', they tend to have shorter, sturdier legs. Many, but not all, species have abdomens more patterned than most Thomisus species, rather like some of the Synema species. Some however, that are more terrestrial, resemble earth in colour and texture.

Most species of the genus Xysticus are small to medium sized spiders. They show a sexual dimorphism in size. Females of typical species reach a maximum of 10 millimetres (0.39 in) of body length, while their males are about 3–5 millimetres (0.12–0.20 in) long, about half the size of the females.

The basic colour of these species is usually brown, beige or gray. The prosoma is sometimes slightly smaller than the opisthosoma. In many species the front body shows in the middle a broad, pale longitudinal band. The opisthosoma is clearly flattened in most species and shows a median broad and dark leaf marking.

The species are often very similar to each other, and in most cases can be distinguished only by a microscopic examination of the reproductive organs.

Members of this genus have a smooth or granulated integument and their colour is cryptic fawn to reddish brown to blend in with the soil surface. The body and legs are covered with simple setae, rarely blunt. The tibiae and metatarsi I and II each have more than three pairs of setae ventrally. They are all cryptic and difficult to identify, with genitalia playing an important role in distinguishing between species.^[1]

• Xysticus audax
• Xysticus kochi, female
• Xysticus cristatus
• Xysticus bilimbatus

As of September 2025, this genus includes 275 species and ten subspecies.^[2]

These species have articles on Wikipedia:

• Xysticus havilandi
• Xysticus lanio
• Xysticus luctator
• Xysticus ninniii
• Xysticus ulmi

• J. H. Redner and C. D. Dondale (1965). A New Species of The Spider Genus Xysticus (Araneae: Thomisidae) From Arizona - Psyche 72(4): 291–294.
• H. Demir, O. Seyyar, and M. Aktaş (2008). A Poorly Known Species of the Spider Genus Xysticus C. L. Koch (Araneae, Thomisidae) in Turkey. Archives of Biological Sciences 60(4): 17P-18P.

• Citizen science observations for Xysticus at iNaturalist
• Xysticus BugGuide