Moths and butterflies may spend the winter in any stage of their lives. Bagworms hibernate as eggs. The eggs are in cocoon-like silken bags about two inches long, hung from the tips of branches. Gypsy moths winter as eggs attached in masses to a piece of wood and covered with scales from the female's body. Viceroy butterflies winter as caterpillars inside a nest made of a rolled leaf fastened to a twig. The caterpillars of the Baltimore butterfly spin a silken tent on top of their food plant and pass the winter within it. The cattail moth winters as a caterpillar inside cattail stalks. The codling caterpillar burrows into an apple, and the corn borer caterpillar spends the winter burrowed into an old cornstalk.

   Pupae are well protected from winter cold by silken cocoons or hard, thick cases. The cecropia, promethea, and polyphemus moths winter in their cocoons. The red admiral butterfly hibernates as an adult in hollow logs. The adult mourning cloak butterfly seeks any shelter available.

   Although the majority of these insects pass the winter in a resting state, some migrate southward. Great numbers of monarch butterflies are seen flying in the autumn. Some scientists believe that these are dispersal movements or simply a scattering of large populations. There is little evidence of a return flight to the north, except possibly by a few battered individuals. The next year's population is built up chiefly by monarchs that remained in the northern climate through the winter.

    Making a collection of butterflies and moths, carefully mounted and accurately labeled, is a fine hobby. It is interesting to raise these insects from eggs and observe their life history. The abundant monarch butterfly is a good species to start with. Any weedy field with milkweed growing in it is a good place to find eggs and caterpillars. They are to be found on the underside of the leaves.

   Do not disturb the eggs or the caterpillar, but pick the plant to which they are attached. Place the plant in a can filled with water to keep the milkweed fresh. Wire such as florists use will hold the weed upright. As the milkweed begins to wither, replace it with a fresh leafy stalk, and let the caterpillar crawl onto it. Monarchs will not eat anything but milkweed, so do not experiment with some other plant.

   After five molts the caterpillar reaches a length of about 2 inches and is ready to pupate. Care must be taken to prevent its escape. In nature it will leave the milkweed and crawl to some high support. Strip off the lower leaves of the plant so that they do not form a bridge across the can. The can and the plant also may be covered with a wire screen.

   On a rib or stem of the plant or on the screen itself, the caterpillar begins to spin its silk button. Through a magnifying glass the silk can be seen issuing from spinnerets in the head. When the button is completed, the caterpillar turns around, attaches the hooks at the end of its body to the silk, and then gradually releases its hold until it is hanging free, upside down. Several hours elapse. When the long antennae at the head end become limp and shriveled, the caterpillar is ready to turn into a pupa. Some time before the old skin is ready to split open, the caterpillar begins to swing and jerk. Suddenly at the top of the head the skin opens, and with thrashing movements the insect rolls it up toward the silk button. What is revealed is a beautiful case of jade green studded with golden dots. The pupa case twitches for about two hours, meanwhile shrinking in size. Finally it becomes still. Pupation is completed.

   In about two weeks the pupa begins to turn dark. When it is black and transparent, the case opens and the butterfly pulls itself free. For breeding monarchs, the adult must be confined to a cage and provided with a mate. It must have sugared water for nourishment and more milkweed on which the female may lay its eggs. If set free, it can migrate, perhaps thousands of miles, with others of its kind.