The arachnids from the late Eocene Insect Limestone of the Isle of Wight are reviewed. Only spiders (Araneae) have been recorded, of which several dozen are known, mostly juveniles. Nearly all are araneomorphs; the putative mygalomorph Eoatypus woodwardii McCook, 1888 was removed from that infraorder by Selden (2001), but new specimens, yet to be described, could belong in this group. Among the adult specimens, which are thus identifiable to family level, most belong to the argyronetid water-spider Vectaraneus yulei Selden, 2001; some resemble araneids, and a small number can be referred to other families. New morphological information on the holotype of Vectaraneus is presented, and three other specimens are described in more detail here, in Segestriidae, Araneidae and Salticidae. Segestriids are nocturnal sedentary hunters living in tubular retreats in rock or bark crevices. Araneids are the archetypal weavers of orb webs. Salticids are the familiar jumping spiders; the one described here is an ant mimic. Their presence suggests a drier habitat was present somewhere in the source environment for the fossil biota, and they were probably inhabitants of the raised hammocks suggested for the Insect Bed palaeoenvironment.

Two orb-web spider species, one diurnal and one nocturnal, were studied and shown to be highly flexible in their behaviour. Flexibility is discussed in relation to improving capture success and avoiding predation. Although earlier studies have revealed that spiders modify web design and web orientation according to light and wind direction, here we show that orb-web spiders can further respond to light and wind direction by choosing a side of the web to reside on. The diurnal species, Argiope keyserlingi, tended to orient its dorsal side into vegetation gaps and towards light, whereas the nocturnal species, Larinioides sclopetarius, tended to expose its dorsal side into the oncoming wind. While orientation on the web had little affect on prey capture success, in A. keyserlingi, orientation into vegetation gaps may reduce attacks by praying mantids which approach the spiders by walking along the vegetation surrounding the web. In contrast, exposing the dorsal side into the wind may increase stability on the web for L. sclopetarius, preventing the spiders from being dislodged from the webs by strong gusty wind.

A number of taxonomically diverse species of araneoid spiders adorn their orb-webs with conspicuous silk structures, called decorations or stabilimenta. The function of these decorations remains controversial and several explanations have been suggested. These include: (1) stabilising and strengthening the web; (2) hiding and concealing the spider from predators; (3) preventing web damage by larger animals, such as birds; (4) increasing foraging success; or (5) providing a sunshield. Additionally, they may have no specific function and are a consequence of stress or silk regulation. This review evaluates the strength of these explanations based on the evidence. The foraging function has received most supporting evidence, derived from both correlative field studies and experimental manipulations. This contrasts with the evidence provided for other functional explanations, which have not been tested as extensively. A phylogenetic analysis of the different decoration patterns suggests that the different types of decorations are as evolutionary labile as the decorations themselves: the analysis shows little homology and numerous convergences and independent gains. Therefore, it is possible that different types of decorations have different functions, and this can only be resolved by improved species phylogenies, and a combination of experimental and ultimately comparative analyses.