Silcox and Stevenson: Modern Nature Study
Hodge: Nature Study and Life
CADDICE-FLY
Time: May.
The caddice-flies are very interesting insects, owing to the habits of the larvæ of building little cases of wood, stones, or shells, in which they pass their development stages under water.
These larvæ are easily found during the month of May in little streams of water everywhere throughout the Province. Look for what at first sight appears to be a bit of twig or a cylinder of stone about an inch long moving along the bottom as though carried by currents. Closer observation will result in the discovery that this is a little case composed of grains, of bits of stick, or of sand and tiny shells, and the head of the occupant may be seen projecting from one end.
Collect some of these larvæ in a jar of water and transfer them to the aquarium. Direct the pupils to look for others in the streams, so that they may observe their appearances and movements in their natural environment. If kept in jars, the water must be changed every day, and the top should be covered to prevent the escape of the adults.
Observe.—The shape of the various kinds of cases; the materials, and how fastened together (chiefly by silk); the part of the larva that protrudes from the case; the movement, and how caused; the fitness of the case as a protection. Note hardness, colour, and shape as protective features.
The pupils will be fortunate if they observe the sudden rise of the larva to the surface of the water and the almost instantaneous change into the four-winged fly.