Sternum (arthropod anatomy)

: sterna) is the ventral portion of a segment of an arthropod thorax or abdomen.

In insects, the sterna are usually single, large sclerites, and external.

However, they can sometimes be divided in two or more, in which case the subunits are called sternites,[1] and may also be modified on the terminal abdominal segments so as to form part of the functional genitalia, in which case they are frequently reduced in size and development, and may become internalized and/or membranous.

For a detailed explanation of the terminology, see [2] Kinorhynchs have tergal and sternal plates too, though seemingly not homologous with those of arthropods.

Sternites on the pleon (abdomen) of a crustacean may be referred to as pleonsternites.