Xysticus acerbus

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.

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.

Naming

Thorell, 1872

Distribution

Europe - There are scattered records in the south. The species is widespread in western and central Europe, but is absent from Scandinavia and has not been recorded from Ireland.

Status

The spider appears to be very local and at most sites only a few specimens have been found, but there now seems to be an increase in distribution and frequency happening, at least in some areas.

Threats are difficult to assess because of its varied habitats, but the loss of unimproved grassland in general is likely to be detrimental.

IUCN: Least Concern

Habitat

The spider occurs in a fairly wide range of grassland habitats, chalk or limestone grassland in Dorset, Hampshire and Somerset, short meadow grassland in Sussex and Glamorgan and sand dunes at Braunton Burrows (Devon). It has also been found on heathland and coastal under-cliff in Dorset. In 2005 numerous juveniles were found at a washlands in South Essex, with one adult being reared through. Both sexes are adult in April and May.

Predators

Preyed upon by the European Ground Beetle