al·der·fly 
(ôldər-flī′)
(ôldər-flī′)n.
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.]