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.
