Largest order of arachnids

Araneae, the taxonomic order containing spiders, is the largest order of arachnids. As of 29 October 2015, some 45,732 species have been officially described and named, and are collectively housed in 114 taxonomic families, but there are many still-undescribed species awaiting formal documentation in museum collections as well as awaiting discovery and collection in the wild. Indeed, it has been estimated that between half and two-thirds of all spider species alive today are still undescribed.

The spider order, Araneae, is the seventh largest taxonomic order of animals, and its members occur on every continent of the world except Antarctica, and exist in every type of habitat except the air and the marine environment. Having said that, although spiders lack wings or other flight-related body structures, by casting forth streams of gossamer into a wind current they can drift considerable distances through the air, even crossing seas – a process known as ballooning.