The number of spider species currently known stands at about 40,000 (Platnick, 2007), of a total of perhaps 170,000 species (Coddington and Levi, 1991). The

worldwide spider fauna is thus still far from completely known, especially in the Neotropics in general, and northern South America and the Caribbean in particular. The spider fauna has not been documented in print at the species level for any Caribbean island, though this has been done at the family level for Trinidad (Sewlal and Cutler, 2003; Cutler, 2005; Sewlal and Alayón, 2007; Sewlal & Alayón 2007; Sewlal 2009 and Sewlal 2010).

Trinidad is separated from South America by only 14 km (the southern passage or Serpent's Mouth), and was part of that continent until the end of the last ice age. Trinidad thus shares a similar climate and biota with Venezuela and the Guianas, but is a fraction the size making it a much more manageable area to sample. Knowledge of the spider fauna of Trinidad is therefore of interest as a guide to the biodiversity in northern South America, and as one of the sources of spiders of the Windward Islands and the rest of the West Indies.

There are currently 50 families and 276 species of spiders known in Trinidad, although the latter is expected to be only a third to a half of the true total. A complete biodiversity survey of the spiders of Trinidad would be a very large project. This study therefore focuses on some of the web-building spiders, one of the three ecological guilds of spiders (the others being long-sighted and short-sighted hunters), since their webs make detection easier.