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
The Covent-Garden Journal Advertiser" that the first number would be issued on 23 November 1751. The release was delayed until January because of work related to the publication of "Amelia". At the time of the publication of the journal, Covent Garden, although formally associated with the theatre industry, was more widely known as London's red light district. Fielding had earlier written "The Covent Garden Tragedy", a mock-tragic play concerning the tale of two prostitutes. The first number of the periodical was published on 4 January 1752, and sold at a price of three pence. For most of its run, the journal was issued