breastbone
From ZooTerms (Dictionary of Invertebrate Zoology)
sternum.
breastbone (noun; Anglo-Saxon breost, front of the chest; ban, bony): 1. The
2. (Arthropoda: Insecta) In certain dipterous larvae, a horny ventral process behind the oral opening, representing the labium; anchor process
See also: sternal spatula.