prescutum

from The Collaborative International Dictionary of English v.0.48

Prescutum \Pre*scu"tum\, n.; pl. {Prescuta}. [NL. See {Pr[ae]-},
   and {Scutum}.] (Zool.)
   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.
   [1913 Webster]