Order Phalangida is a term used to describe a group of arachnids commonly known as harvestmen or daddy long legs. In scientific terms, they are also called Opiliones. There are various synonyms for the Order Phalangida, including the Old World harvestmen, cheliferous harvestmen, and the arachnid harvestmen. These synonyms reflect the diverse geographical distribution of harvestmen and the various morphological characteristics that distinguish them from other arachnids. The Order Phalangida comprises over 6,500 species with diverse behavioral patterns, ecological niches, and phylogeny. Despite their varied characteristics, all harvestmen have a similar body plan consisting of a fused thorax and abdomen and unique elongated legs.