diff orb WEB NEW

diff orb WEB NEW - Optimal Area Use in Orb Webs of the...

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90 Naturwissenschaften 87, 90–93 (2000) Q Springer-Verlag 2000 Optimal Area Use in Orb Webs of the Spider Araneus diadematus T. Krink Department of Computer Science, Aarhus University, Ny Munkegade B 540, 8000 Aarhus C, Denmark e-mail: krink 6 daimi. au.dk, Tel.: c 45-89-423358, Fax: c 45-89-423255) F. Vollrath Department of Zoology, South Parks Road, Oxford OX1 3PS, UK Received: 26 April 1999 / Accepted in revised form: 26 November 1999 Abstract We studied the abilities of the garden cross spider Araneus diadematus regarding adapta- tion of web geometry to spatial constraints. Spiders reacted to a spatial reduction in their building site from a square-shaped frame to a slimmer, rectangu- lar frame (side ratio 1:2) by maintaining overall web geometry while reducing the web area covered by the sticky capture spiral. However, when the frames were changed further to a rectangular side ratio of 1:3, the spiders changed specific web properties in such a way that a further reduction in the capture spiral area was prevented. Construction of the threads making up the web frame and the auxiliary spiral requires that the spider explores the spatial constraints of its building site. The geometry of both frame and auxiliary spiral threads in turn determine the geometry of the capture threads. Since in very narrow frames the spider adjusted the auxiliary to suit the subsequent capture spiral, we suggest that an initial spatial survey led to the final adaptation of overall web geometry to a web site. Introduction The garden cross spider Araneus diadematus is able to adapt its highly structured orb web to the envi- ronmental conditions. Factors influencing web con- struction are numerous and varied. They include ex- ternal variables such as prey type (Schneider and Vollrath 1998) as well as wind, humidity, tempera- ture and spatial constraints of the building site (Vollrath et al. 1997). They also include internal var- iables such as weight, size and state of hunger (Voll- rath and Samu 1997; Witt et al. 1972). Thus, al- though the building behaviour follows a fixed gener- al schema, it clearly has the ability for special local adaptations. The orb web of a spider such as Araneus is con- structed by the spider first laying the lines that form the spokes (or radii) and frame threads. The radii are then linked by a scaffolding auxiliary spiral laid from the inside out. This temporary spiral is super- seded (and in the process cut down) by the perma- nent and sticky capture spiral built from the outside in. The entire process consists of a sequence of be- haviour patterns that rely on measuring geometric parameters such as distances and angles (Witt et al. 1972); it might conceivably be using path integration (Peters 1937). It can be shown that A. diadematus constructs a web with spatial information that is ex- clusively local (Krink and Vollrath 1999b). Howev- er, the spiders also seem to be able to use global in- formation, for example, by first inspecting a web
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This note was uploaded on 01/27/2012 for the course ECOLOGY 300 taught by Professor Zumdahli during the Spring '11 term at St. Mary NE.

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diff orb WEB NEW - Optimal Area Use in Orb Webs of the...

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