Fibrous and adhesive components of the orb webs of Araneus trifolium and Argiope trifasciata.

The minimum number of secretion products used by the spiders Araneus trifolium and Argiope trifasciata to construct their orb webs has been established by selective enzyme digestion and histochemical staining, as well as differential isotope localization in these webs. Three fiber types are present in the webs: (a) a major fiber found throughout the web, (b) a minor fiber found only in radial threads, and (c) the core fibers of the sticky spiral thread. Three nonfibrous secretions are found on these fibers. These include a water soluble viscid coating of the sticky spiral and two adhesives which fasten the threads of the web together; one found only at junctions of sticky spiral and radial threads and the other at all other thread connections. The possible glandular sources of these secretions are discussed.