Xysticus lanio

Appearance

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.

A ground crab spider with earthy coloration
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.

Naming

C.L.Koch, 1835

Distribution

The genus Xysticus is distributed almost worldwide, but has not been recorded from South America. Of the about 360 species of the genus currently described, about 71 are present in Europe.

Status

Least Concern
In the UK despite some reports in literature that this is a common spider, this species is generally scarce, but may be fairly common in woodlands in parts of the south. In some southern counties such as Essex, it is definitely rare. There is some evidence of decline in the last 30 years.

Behavior

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.

Habitat

The only member of the genus usually to be regularly found on bushes or young trees in woodland, especially favouring young oaks. Adults of both sexes are found mainly between April and June, occasionally later.