Understanding the web construction behaviour of theridiid (comb-footed) spiders is fundamental to formulating specific evolutionary hypotheses and predictions regarding the reduction of orb-webs. We describe for the first time in detail the web construction behaviour of Achaearanea tepidariorum , Latrodectus geometricus , Theridion sisyphium and T. varians as well as webs of a range of other theridiids. In our survey we distinguish four major web types. Among webs with gumfooted lines, we distinguish between webs with a central retreat ( Achaearanea -type) and those with a peripheral retreat ( Latrodectus -type). Among webs without gumfooted lines, we distinguish between those which contain viscid silk ( Theridion -type) and those with a sheet-like structure, which do not ( Coleosoma -type). Theridiid gumfoot-webs consist of frame lines that anchor them to surroundings and support threads which possess viscid silk. Building of gumfooted lines constitutes a unique stereotyped behaviour and is most probably homologous for Nesticidae and Theridiidae. Webs remained in place for extended periods and were expanded and repaired, but no regular pattern of replacement was observed. We suggest that the cost of producing and maintaining viscid silk might have led to web reduction, at least in theridiids.ADDITIONAL KEYWORDS: behavioural patternscharacter evolutioncapture threadresource allocation viscid silkweb constructionweb reduction. Figure 8. Schematic representation of theridiid webs (not to scale): A, Achaearanea-type web with a central retreat. B, Latrodectus-web with a peripheral retreat. C, Theridion-type web with viscid elements. D, Coleosoma-type without viscid elements but with a sheet and KN structure.Benjamin SP, Düggelin M, Zschokke S. 2002. Fine structure of sheet-webs of Linyphia triangularis (Clerck) and Microlinyphia pusilla (Sundevall), with remarks on the presence of viscid silk. Acta Zoologica 83: 49-59. Benjamin SP, Zschokke S. 2002. A computerised method to observe spider web building behaviour in a semi-natural light environment. In: Toft S, Scharff N, eds. European Arachnology 2000. Aarhus, Denmark: University of Aarhus Press, 177-122. Breed AL, Levine VD, Peakall DB, Witt PN. 1964. The fate of the intact orb web of the spider Araneus diadematus Cl. Behaviour 23: 43-60. Bristowe WS. 1958. The world of spiders. London: Collins. Carico JE. 1986. Web removal patterns in orb-weaving spiders. In: Shear WA, ed. Spiders -webs, behavior, and evolution. Stanford: Stanford University Press, 306-318. Coddington JA. 1986. Orb webs in non orb weaving ogrefaced spiders (Araneae: Dinopidae): a question of genealogy. Cladistics 2: 53-67. Comstock JH. 1940. The spider book. Ithaca, NY: Comstock Pub. Assoc. Eberhard WG. 1972. Observations on the biology of Achaearanea tesselata (Araneae: Theridiidae). Psyche: A Journal of Entomology, Boston 78: 209-212. Eberhard WG. 1979. Argyrodes attenuatus (Theridiidae): a web that is not a snare. Psyche: A Journal of Entomology, Boston 86: 407-413. Eberhard WG. 1981. The single ...

The fragmentation of natural habitats is generally considered to be a major threat to biodiversity. We investigated short-term responses of vascular plants (grasses and forbs) and four groups of invertebrates (ants, butterflies, grasshoppers and gastropods) to experimental fragmentation of calcareous grassland in the north-western Jura mountains, Switzerland. Three years after the initiation of fragmentation - which was created and maintained by mowing the area between the fragments - we compared species richness, diversity and composition of the different groups and the abundance of single species in fragments of different size (area: 20.25 m, 2.25 m and 0.25 m) with those in corresponding control plots. The abundances of 19 (29%) of the 65 common species examined were affected by fragmentation. However, the experimental fragmentation affected different taxonomic groups and single species to a different extent. Butterflies, the most mobile animals among the invertebrates studied, reacted most sensitively: species richness and foraging abundances of single butterfly species were lower in fragments than in control plots. Of the few other taxonomic groups or single species that were affected by the experimental fragmentation, most had a higher species richness or abundance in fragments than in control plots. This is probably because the type of fragmentation used is beneficial to some plants via decreased competition intensity along the fragment edges, and because some animals may use fragments as retreats between foraging bouts into the mown isolation area.

Arthropods in several orders use traps to capture prey. Such trap-building predators expend most of their foraging energy prior to any prey contact. Nevertheless, relative investments in trap construction and actual prey capture may vary among trap builders, and they are likely to face a trade-off between building very effective but energetically costly traps and building less effective traps requiring faster reaction times when attacking prey. We analysed this trade-off in a field experiment by comparing the prey capture behaviour of four different sympatric web-building spiders (Araneae: Araneidae, Nephilidae, Tetragnathidae, Theridiidae) with the retention times of five different prey types in the webs of these spiders. Retention times differed greatly among webs and among prey types. The vertical orb webs retained prey longer than the horizontal orb web and the sheet web, and active prey escaped more quickly than less active prey. Among spiders with orb webs, the spider with the web that retained prey for the shortest time was the fastest to capture prey, thus confirming the expected trade-off between building long-retaining webs and attacking slowly versus building short-retaining webs and attacking more rapidly. The sheet web, however, neither retained prey for an appreciable period of time nor facilitated rapid prey capture. We suggest that this low capture effectiveness of sheet webs is compensated by their lower maintenance costs.

Web-building spiders are an important model system to address questions in a variety of biological fields. They are attractive because of their intriguing biology and because they can be fairly easily collected and maintained in the laboratory. However, the only published instructions for working with web-building spiders are somewhat outdated and not easily accessible. This paper aims to provide an up-to-date guide on how to best collect, keep and study web-building spiders. In particular, it describes how to obtain spiders by capturing them or by raising them from cocoons, how to keep and feed spiders in the laboratory and how to encourage them to build webs. Finally it describes how to document and analyze web building and web structure.

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