Spider are apparently absent. In some species, the exocuticle of the legs and prosoma is modified by a tanning process, resulting in brown coloration. Bilins are found, for example, in "Micrommata virescens", resulting in its green color. Guanine is responsible for the white markings of the European garden spider "Araneus diadematus". It is in many species accumulated in specialized cells called guanocytes. In genera such as "Tetragnatha", "Leucauge", "Argyrodes" or "Theridiosoma", guanine creates their silvery appearance. While guanine is originally an end-product of protein metabolism, its excretion can be blocked in spiders, leading to an increase in its storage. Structural colors
Araneus quadratus wooded areas, or wherever there is vegetation to string an orb web across. This species builds its web close to the ground to catch jumping insects such as small grasshoppers. The female builds the more elaborate web, complete with a funnel-shaped retreat off to the side where she goes during inclement weather. The web is smaller and closer to the ground than those of other species of orb-weaver. Adult females can actively change their color. It takes about three days to take on colors that accurately match their resting surface. Araneus quadratus Araneus quadratus, the four-spot orb-weaver, is a common