Certain spider webs are composed of several types of micro-optical elements made from transparent optical materials.
The silks (radial and capture) are almost exclusively protein. The nearly cylindrical silks have diameters in the range 0.1
to several microns and cross-sectional morphology that is cylindrical-multi-layered,.as studied by transmission electron
microscopy, The capture threads are coated with aqueous adhesive that also forms into nearly elliptical micro-lenses
(adhesive droplets) mounted on the near cylindrical silks. The remaining elements of the web are the cement junctions
tying the radial and the capture threads of the web together. These are irregularly shaped platelets. Progress to date on
our research characterizing the optical properties and function of these transparent orb webs has been to interpret the
reflection and transmission properties of the elements of the web, and the web as a whole, in natural lighting; to evaluate
the optical finish of the surface of the silks and capture droplets; and to measure the principal refractive indices of radial
silks using new immersion based methods developed for application to micron-sized, curved optical elements. Here we
report the principal refractive indices, birefringence, dispersion and morphology of transparent spider silk subject to
various chemical treatments. The morphology is measured using TEM. Insight into the physical origin of the refractive
index properties will be discussed.