alderfly

[awl-der-flahy]
noun, plural al·der·flies.
  1. any of several dark-colored neuropterous insects of the family Sialidae, the larvae of which are aquatic and predacious on other aquatic insects.

Origin of alderfly

First recorded in 1820–30; alder + fly2
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018