AQUARIUM SPECIMENS
MOSQUITO
Time.—May or June.
Questions and Observations.—At what time of the year are mosquitoes most plentiful? In what localities are they most plentiful? Why are they most plentiful in these places? Are mosquitoes ever seen during fall or winter? How do you account for their rapid increase in number early in summer?
How do mosquitoes find their victims? Observe the humming noise and try to discover how it is made.
Watch a mosquito as it draws blood from your hand. Does the point of the beak pierce the skin?
Capture a number of mosquitoes and place them in a jar containing some water and a few straws or sticks standing upright out of the water. Cover the mouth of the jar with a glass plate or fine gauze. Watch for the rafts of mosquitoes' eggs on the surface of the water.
The eggs may also be found on the surface of ponds or open rain barrels, and may be transferred to water in a jar in the laboratory.
STUDY OF THE ADULT FORM
Note the shape, colour, sucking tube, wings, and legs. Compare with the house-fly.
Distinguish the male insect from the female; the former has feathery feelers, and has mouth parts unsuited for biting.
How many kinds of mosquitoes have you seen? Direct attention to the kind which causes the spread of malaria. It is recognized by its habit of standing with its body pointing at right angles to the surface on which its feet are placed or, in other words, it appears to stand on its head.
THE DEVELOPMENT
Describe the egg raft.
Observe the wigglers (hatched in about a day); the divisions of the body of the wigglers; position of the wigglers when at rest. Observe that the tail end is upward. Lead the pupils to perceive that this is the means of getting air.
Observe the rapid movement toward the bottom when disturbed; the means of causing this movement; the change into the large-headed pupæ—a change which takes place about ten days after hatching; the almost motionless character of the pupæ; the change from the pupæ forms into the adult—a change which takes place at about the fourth day of pupæ life.
Put some mosquito larvæ (wigglers) into the fish aquarium. Are mosquitoes of any use? The wigglers are the food on which some young fishes live. Young bass and trout feed upon them.
Put some kerosene on the surface of a jar in which there are mosquito larvæ. Describe a method of destroying mosquitoes.
The teacher tells about the mosquito as the cause of the spread of malaria. From the fact that the eggs hatch on stagnant water, deduce a benefit arising from the draining of land.
REFERENCES
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.