Source : Webster's Revised Unabridged Dictionary (1913)

Tanystomata \Tan`y*stom"a*ta\, n. pl. [NL., fr. Gr. ? to stretch
   + ?, ?, mouth.] (Zo["o]l.)
   A division of dipterous insects in which the proboscis is
   large and contains lancelike mandibles and maxill[ae]. The
   horseflies and robber flies are examples.