Observation

A. Verrill Hyatt , Rivers and their mysteries , New York, Duffield and company, 1922, p.140-141

We look closer and discover that the object is a little bunch of twigs is motionless and seems devoid of life, but if we place it in a little pool of water we will presntly see a small head appear from one end of the object and a moment later it will commence to move slowly along, for this is the home of a caddice worm, the larvae of a pretty lacewinged insect. Our interest now aroused, we search our pool for more specimens and find them aplenty ; caddice worms in house of twigs, in houses of sand, in houses built of tiny shells and, in one corner between two little pebbles, we see what we mistake for …..