Alderflies are typically mistaken for small hellgrammites as larvae and large caddisflies as adults. They turn up often enough in nymph samples that it's nice to know what they look like. There are rumors of their occasional importance to trout, but the average anglers is not likely to encounter it. Where & WhenTime Of Year (?): Early season
24 species aren't included.
Hatching BehaviorPupae burrow into the ground near to, but not in, the stream. Because the emergence takes place on land it is unimportant to trout.Egg-Laying Behavior
Time Of Day: DaytimeThe mating adults gather over the water in good numbers but do not usually fall into the water unless wind knocks them off course.
They lay their eggs on dry objects near the water. Ernest Schwiebert describes their egg placement in Matching the Hatch:
The egg masses are deposited on rocks, limbs, leaves and bridges where they are over running water and in the sunlight. They are placed so that the hatching larvae fall into the stream.Larva & Pupa Biology
Current Speed: SlowThe larvae are burrowers like the Ephemeridae mayfly nymphs, digging down into the silt.
Pictures of 5 Alderfly Specimens in the Genus Sialis:
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