Difference between Spiders and OpilionesIntroductionAlthough spiders and Opiliones are arthropods and belong to the same animal class – Arachnids – opiliones are not spiders. Opiliones, sometimes confused with spiders, are known by some as "reapers"; others call them “daddy long legs.” Spiders in the Pholcidae family are also called “daddy long legs,” but they are more commonly called “cellar spiders.” (3) People confuse these two long-legged arachnids, and although they may look similar, many differences have been discovered and observed in all aspects of their lives. Body Spiders have two visible body segments: the cephalothorax, which is the rounded section of the head, and the cylindrical abdomen. (2) The body of opiliones appears to have a single oval-shaped body segment, but this is because it is difficult to discern a junction between the head and abdomen. (3) Spiders vary greatly in size, but the average body length of the cellar spider is less than half an inch and its legs can reach 1.25 inches. In comparison, opiliones, or reapers, have a body length of about half an inc...