Movements of adult aquatic insects near streams in Southern Ontario

Sticky traps placed across a stream in southern Ontario in June and September showed that only females of the mayfly Baetis intercalaris and the caddisfly Lype diversa were flying upstream and so conforming to the concept of the colonization cycle. Other species, B. vagans, Cheumatopsyche oxa, C. campyla, Hydroptila consimilis, Chimarra aterrima and Polycentropus centralis seemed to be flying at random along the stream. There was a distinct downstream movement of Baetis subimagos near the water surface. It is shown that a series of 4 traps across the stream gives a better indication of directional movement than a single one.In March the winter stonefly Allocapnia vivipara was shown to walk away at approximately right angles to the stream and to ascend trees at the edge of the woods 16 m away.