sternite

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A sclerite making up part of the sternum of an arthropod.

from The Century Dictionary.

• noun In Arthropoda, as an insect or a crustacean, one of the median ventral sclerites of the crust or body-wall; the median ventral piece of any segment, somite, or metamere, whether a distinct piece or only that undistinguished ventral part or region which lies between the insertions of any pair of legs or other appendages.
• noun In entomology, specifically, the under or ventral sclerite of an abdominal segment.
• noun One of the pieces of the sternum or breastbone of a vertebrate; a sterneber.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) The sternum of an arthropod somite.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The ventral plate of each segment of an arthropod