Insects that are not of aquatic origins. Commonly blown into the water with the wind, or when startled. Others fall in from branches above. There are many different taxa in various sizes. Population numbers vary through spring, summer, and autumn, often peaking during a species-specific time period. Look around before you cast.
Hymenoptera, Bees, Hornets and Wasps
Various species and sizes. Not infrequent addition to stream drift and a good source of protein. Various colors. Sizes 8-24