The Collaborative International Dictionary of English v.0.48:

Tracheobranchia \Tra`che*o*bran"chi*a\, n.; pl.
   Tracheobranchlae. [NL. See Trachea, and Branchia.]
   (Zool.)
   One of the gill-like breathing organs of certain aquatic
   insect larvae. They contain tracheal tubes somewhat similar
   to those of other insects.
   [1913 Webster]