Calculation of capture thread length in orb webs

This study provides ecologists and ethologists with an accurate tool to investigate the web investment of orb web spiders in the field. A crucial foraging investment for orb web spiders is the length of silk invested in each web. However, the different types of orb web silks have different costs for the spiders and must be treated separately. As the viscid silk material used to construct the capturing spiral in webs is more costly to produce and more likely to become limited than other types of silk, our study focuses on the length of these capture threads. We evaluate 3 formulae used to calculate capture thread length, by comparing their estimates with the actual total capture thread length measured from photographs of Nuctenea sclopetaria Clerck webs. The formulae used are from the literature and newly proposed ones. The results suggest the use of a newly proposed formula that not only provides agreement with the actual thread length but also is efficient and convenient for field studies.