| | The spider families of Britain and Ireland |
Excluding Philodromidae
Crab Spiders.
Morphology. The adult spiders 2–10 mm long; mostly decidedly plump-bodied, or of medium build (in some males); decidedly short-legged, or with legs of medium length, or decidedly long-legged (from about as long as the body to over three times as long); markedly crab-like in stance and locomotion; with eight eyes (black and beady, occasionally dark blue-grey). The eyes in two horizontal rows of 4 (the laterals often on tubercles); all dark. The palpal organs of the male of complex structure and enclosed by the specialized, hollowed tarsal segment (the cymbium). The front legs not short and stout. The first two pairs of legs forwardly directed, laterigrade; conspicuously longer and often stouter than the third and fourth pairs (resulting in the characteristic, crab-like stance and sideways locomotion). Metatarsus IV of the females without a calamistrum. Scopulae absent. Tarsal claws 2. The tarsi without claw tufts. The abdomen angular in shape (sometimes, e.g. in Thomisus onustus), or angular in shape; conspicuously patterned dorsally (usually, occasionally green), or plain dorsally; occasionally exhibiting red or pink colour, but neither predominantly bright red and black nor predominantly bright red and yellow (or at least pink, e.g. in female Thomisus onustus), or without any red coloration; with a single, inconspicuous tracheal spiracle. The anterior spinnerets close together. The abdomen of the females without a cribellum. The reproductive openings of the females associated with an epigyne.
The adults not making snare-webs; lying in wait for their prey (on the ground, in vegetation or in flowers, often cryptically coloured and some, e.g. Misumena vatia, actively changing colour to match the background; the prey being seized with the large and often spiny front legs).
Representation in Britain and Ireland. 25 species in Britain; in the genera Diaea, Misumena, Ozyptila, Pistius, Thomisus, and Xysticus.
Comments. These species have legs I and II longer and stouter than III and IV, reflecting the characteristic, crab-like posture and locomotion.
Illustrations. • Diaea, Ozyptila, Thomisus and Xysticus. 37, Thomisus brevipes Bl., probably = Xysticus luctuosus (Bl.), female (see 45 for male). 38, Xysticus cristatus (Clerck): a, female; b, male; c, eyes; d, maxillae and lip; e, lateral view of cephalothorax and abdomen, in outline; f, claw of anterior leg; g, claw of palpus; h, male palpal organs. 39, Xysticus audax (Schr.), female. 40, Xysticus erraticus (Bl.): a, male palpal organs. 41, Xysticus sabulosus (Hahn): a, immature female (cf. 43); b, male; c, palpal organs of the male. 42, Thomisus atomarius Walck. (= ? - identity uncertain): female. 43, Xysticus sabulosus (Hahn), mature female (cf. 41). 45, Xysticus luctuosus (Bl.), male; a, palpal organs. 46, Xysticus bifasciatus (C.L.K.): a, female; b, male; c, palpal organs of the male. 47, Xysticus luctator (L.K.), female. 48, Ozyptila atomaria (Panz.), female (see also the next image, 49). From Blackwall (1861, with approximate lengths of females added). • Diaea, Misumena, Ozyptila, Thomisus. 44, Diaea dorsata Fabr.: a, female; b, male; c, palpal organs of the male. 49, Ozyptila atomaria (Panz.): a, female; b, male; c, palpal organs of the male (see also the preceding image, 48). 50, Ozyptila trux (Bl.), male; a, palpal organs. 51, Ozyptila praticola (C.L.K.): a, female; b, male; c, palpal organs of the male. 52, Ozyptila blackwalli Simon: a, female; b, male; c, palpal organs of the male. 53, Misumena vatia Clerck: a, female; b, male; c, palpal organs of the male. 54, Thomisus onustus Walck., female: a, side view of the cephalothorax, showing one of the projections on which the lateral eyes are seated; b, the frontal margin. From Blackwall (1861, with approximate lengths of females added).
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. The spider families of Britain and Ireland. Version: 5th August 2019. delta-intkey.com’.
