Biology Faculty Research


Estimation of Capture Areas of Spider Orb Webs in Relation to Asymmetry

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We examined the utility of several popular formulae used to estimate the capture areas of orb webs across a large sample of Cyclosa Menge 1866 and Tetragnatha Latreille 1804 webs. All formulae evaluated contained at least some bias in estimation of the capture areas of webs. We identified two types of asymmetry in orb webs that affect capture area estimation differently. Web asymmetry measures the ratio of the horizontal and vertical diameters of orb webs while hub asymmetry measures the displacement of the hub from the geometric center of a web. An analysis of model webs that varied in web and hub asymmetry showed that most formulae overestimated capture area as web asymmetry increased and that some formulae also overestimated capture area as hub asymmetry increased. Only the "Ellipse-Hub" formula was unaffected by web and hub asymmetry. Although the "Adjusted Radii-Hub" formula provided a slightly more accurate overall estimate of capture area, we recommend that the "Ellipse-Hub" formula be used when comparisons of capture area are made between taxa or individuals that vary in web and hub asymmetry.

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Journal of Arachnology





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