Webster's Revised Unabridged Dictionary · 1913

alderfly

alderfly

1.
Any of numerous dark-colored neuropterous insects of the genus Sialis or allied genera. They have predaceous aquatic larva, which are used for bait.
2.
(Angling) An artificial fly with brown mottled wings, body of peacock harl, and black legs.

Also: Alder fly