Ricinulei are known as hooded tick-spiders. There are between 50 – 60 species of ricinuleids, all in one family (Ricinoididae). They occur in the rainforests of western and central Africa and in caves and forests from Texas to Peru. Fossil ricinuleids date back to the Carboniferous of Euramerica and the Cretaceous Burmese Amber.
These small arachnids (5 – 10 mm in length) have very thick, sculptured cuticle. The pdeipalps are short and end in pincers. They are active at night and all species are thought to be either completely lacking eyes or with just a pair of pale, light-sensitive organs. They are called hooded tick-spiders because their chelicerae (jaws) are covered with a hinged hood-like plate called the cucullus.
Ricinuleids have a locking mechanism between the prosoma (head region) and opisthosoma (2nd body part) that can be unhooked curing mating and egg laying. The 3rd leg of the male is specialized for sperm transfer. Ricinuleids have six-legged nymphs (1st post-egg larval stage), similar to Acarina. They can live 5 – 10 years.