tracheobranchia

from The Century Dictionary.

• noun A breathing-organ of certain aquatic insect-larvæ, combining the character of a gill with that of an ordinary trachea.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) One of the gill-like breathing organs of certain aquatic insect larvæ. They contain tracheal tubes somewhat similar to those of other insects.