alderfly(redirected from Alderflies)
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Any of various insects of the family Sialidae, having two pairs of dark many-veined wings, long antennae, and aquatic larvae.
[Probably so called because the mature insects can be found resting on foliage in the moist habitats near lakes and streams where alders typically grow.]
(Animals) any of various neuropterous insects of the widely distributed group Sialoidea, such as Sialis lutaria, that have large broad-based hind wings, produce aquatic larvae, and occur near water