idiosoma

The idiosoma is the posterior part of the body in arachnids, also known as the abdomen or opisthosoma. It is one of the two main body segments, the other being the cephalothorax (prosoma). The idiosoma contains vital organs such as the gut, heart, and reproductive organs. In some arachnids, like scorpions, the abdomen is further divided into a mesosoma (preabdomen) and a metasoma (postabdomen). The size and segmentation of the idiosoma vary greatly among different arachnid species. For example, in mites and ticks, the body is often rounded with no visible segmentation, while in spiders, the abdomen is attached to the cephalothorax by a narrow stalk called a pedicel. The idiosoma generally lacks appendages, with the exception of spinnerets in spiders.1234567