Xysticus cristatus, Common ground crab spider

Xysticus cristatus (Clerck, 1757) (Common ground crab spider)

≤ 1900

1901-1979

1980-2005

2006 ≤

Description: The dark triangle on the carapace extends back about two thirds of the length of the carapace from the posterior row of eyes, and ends in a well-defined dark point. The female abdomen is very variable in colouration and markings. Male as female but smaller and darker. Size: Female 6-8 mm; male 3-5 mm.

Genus: Xysticus C. L. Koch, 1835. (Ground crab spiders). Characters of genus: These spiders are medium sized and crablike. Most species are in various shades of brown and grey with patterns made of white and yellow blotches and bars. Males are often darker than females and with more vivid tints. The carapace is brownish with central whitish-yellow band enclosing a darker triangle behind the posterior eyes and pointing backwards. The carapace is armed with long black spines which are round, Hereby they differ from the related genus, Ozyptila which have short blunt or clavate spines. The median ocular trapezium forms almost a square or is slightly wider than long. The anterior lateral eyes are clearly larger than the rest, the lateral eyes of both rows on independent tubercles. The abdomen is wider at rear bearing a folium dorsally and usually with white blotches and transverse bars. The legs are short, stout and spiny. Most species ambush prey on low vegetation, while others are found in leaf litter, under stones and bark.

Family: Thomisidae Sundevall, 1833 (Typical Crab Spiders). Characters of family: The thomisids belong to the group of araneomorph, ecribellate spider families having 8 eyes and 2 tarsal claws. The eyes are arranged in two recurved rows of four with the posterior row usually more curved than the anterior row. The median eyes are the smallest, the laterals on confluent tubercles, with the posterior laterals facing somewhat backwards. The secondary eyes are provided with tapetum. Thomisids belong to a morphologically very diverse family of spiders generally characterized by broad, moderately flattened carapace and abdomen. The carapace is about as long as wide being semicircular, ovoid or slightly elongated sometimes with protuberances. Usually, it is thinly covered by a few erect simple or clavate setae sometimes arising from warts. Most species have lateral bands on the carapace; sometimes the bands reach the edge. The sternum is heart-shaped. Chelicerae are relatively small and weak, adapted for quick kills by biting prey in the head. Cheliceral teeth are absent except in one subfamily. Sometimes there are small teeth (denticles) present on promargin. Endites and labium are frequently longer than wide. Legs I and II are longer and sturdier than legs III and IV. Legs articulate in plane of the body (laterigrade legs). The anterior legs are often provided with series of strong spines on tibia and metatarsi (e.g. Xysticus and Ozyptila). The abdomen is variable in shape and colour. It may be round, ovoid or elongate, nearly always widest at rear half. It is often covered by scattered simple setae or clavate hairs. Abdominal colours vary from bright hues of white, yellow, green, and pink to shades of grey and brown in obscure patterns. The anterior spinners are short and conical and situated close together. A colulus is present in front of the spinners. The tracheal spiracle is situated close to the spinners. The epigyne is small and weakly sclerotized in some species. The epigynes of Xysticus species can be highly variable in depth of sclerotization within the same species and females are therefore sometimes difficult to identify by examination of epigynes. The tibia of the male palp is provided with ventral and retrolateral apophyses. Embolus is often long and curved along the rim of the cymbium.

Female

Female with egg sack

Female

Male

Female

Male

Female