• (n.) The first of the four pieces composing the dorsal part, or tergum, of a thoracic segment of an insect. It is usually small and inconspicuous.
Pre·scu'tum noun ; plural Prescuta [ New Latin See Præ- , and Scutum .] (Zoology) The first of the four pieces composing the dorsal part, or tergum, of a thoracic segment of an insect. It is usually small and inconspicuous. 
the anterior dorsal sclerite of a thoracic segment of an insect.