The METASOMA is the posterior part of the body, or tagma , of arthropods whose body is composed of three parts, the other two being the prosoma and the mesosoma . In insects, it contains most of the digestive tract , respiratory system , and circulatory system , and the apical segments are typically modified to form genitalia . In a few of the most primitive insects (the Archaeognatha ), the metasomal segments bear small, articulated appendages called "styli", which are often considered to be vestigial . There are also pre-apical appendages in most insect orders, called cerci , which may be multi-segmented and almost resembling a posterior pair of antennae ; these may be variously modified, or lost entirely. Otherwise, most adult insects lack appendages on the metasoma, though many larval insects (e.g., caterpillars ) have some form of appendages, such as prolegs or, in aquatic insects, gills .
In scorpions , the metasoma is the tail. In other chelicerates, such as spiders , the mesosoma is fused with the metasoma to form the opisthosoma .
* ^ A B D. R. Khanna & P. R. Yadav (2004). "Segmentation in
arthropods". Biology of Arthropoda. Discovery Publishing House . pp.
316–394. ISBN 978-81-7141-897-8 .
* ^ Donald L. J. Quicke (2009). "