Sternum (arthropod anatomy)
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, 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 
Ventrites are externally visible sternites. Usually the first sternite is covered up, so that vertrite numbers do not correspond to sternid numbers.
The term is also used in other arthropod groups such as crustaceans, arachnids and myriapods. Sternites on the pleon (abdomen) of a crustacean may be referred to as pleonsternites. These are the sites of attachment of the pleopods (swimming legs). In spiders, the sternum is the ventral part of the cephalothorax.
- W. Patrick McCafferty (1983). "Identifying aquatic insects". Aquatic Entomology: the Fishermen's and Ecologists' Illustrated Guide to Insects and their Relatives. Jones & Bartlett Publishers. pp. 17–27. ISBN 978-0-86720-017-1.
- Hood (1958). "THE TERMS TERGUM AND STERNUM, TERGITE AND STERNITE" (PDF).
- Sørensen, M. V. et al. Phylogeny of Kinorhyncha based on morphology and two molecular loci. PLoS One 10, 1–33 (2015).