A Comparative Study of the Supercontraction of Major Ampullate Silk Fibers of Orb-Web-Building Spiders (Araneae)

An improved and simple technique is described for determining the magnitude of the recentl y observed phenomenon of supercontraction of major ampullate silk fibers of orb-web-building spiders . Supercontraction ratios obtained by the use of that method and also from an instrumental method are given . It is seen that only three levels of supercontraction are found among twenty two species of orb-web-building spiders. The data are presented on the basis of taxonomic classification and ar e subjected to statistical analyses in order to determine which ones may be effectively differentiate d from the others . A contribution to the integerity of the wetted web is suggested as a function for the retractive driving force which underlies supercontraction. Mention is made of the possible usefulnes s ofsupercontraction as a taxonomic symptom .