Fine structure of cribellate spider silk

Sticky silk from webs of the spiders, Uloborus diversus and Filistata arizoniciis,were examined by election microscopy. The silk of U. diversus contains long fibrils, 200 –300 A˚ in diameter, consisting of an electron-dense central filament, 30 –60 A˚ across, embedded in a lighter matrix. Transverse banding is distinguished in the matrix at intervals from over 200 to less than 50 A˚. Similar features are observed in the silk of F. arizonicus . Extended fibrils have an altered structure.