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 Theridiosomatidae ("Theridiosoma gemmosum", described by L. Koch, 1877 as "Theridion gemmosum"), Titanoecidae ("Nurscia albomaculata", described by Lucas, 1846 as "Epeira albo-maculata") and Uloboridae ("Uloborus glomosus", described by Walckenaer, 1842 as "Epeira glomosus"). "Epeira cylindrica" was at a time placed in Linyphiidae and is considered "incertae sedis", as is ""Araneus" cylindriformis" . "Epeira" was synonymized with the genus "Aranea" by Leach, 1815, and with "Araneus" by Simon, 1904. Throughout the 19th century, "Epeira" was used as a catch-all genus, similar to the once ubiquitous salticid genus "Attus". However, from 1911, to its last mention in 1957, only very few authors continued