Harvestman

Opiliones are an order of arachnids commonly known as harvestmen. As of 2006, over 6,400 species of harvestmen have been discovered worldwide, although the real number of extant species may exceed 10,000. Well-preserved fossils have been found in the 400-million-year-old Rhynie cherts of Scotland, which look surprisingly modern, indicating that the basic structure of the harvestmen has not changed much since then.
Although they belong to the class of arachnids, harvestmen are not spiders, which are of the order Araneae rather than the order Opiliones.