1. Cabbage-white butterflies.—(a) The eggs.—In May or September, search the leaves of cabbages, turnips, and other crucifers (p. 95) for the tiny eggs of cabbage-white butterflies. Do the eggs occur singly or in clusters? Are they found on the upper or the lower surface of the leaf? Cut off a piece of leaf which carries eggs, put it under a tumbler, and examine it every day until the larvae (caterpillars) emerge from the eggs. (b) The larva.—Have ready a “breeding-cage,” i.e. a box measuring, say, 18” × 8” × 6”, one large face of which is of perforated zinc or fine wire gauze, and the other of glass; the box should be without bottom, so that it can be placed over a food-plant. Put the larvae, with leaves of the plant on which they were found, under the box, and observe them carefully. Replace all rotted or soiled leaves by fresh ones. It is best to keep the food-plant in a bottle of wet sand inside the case; the leaves then remain fresh for several days. Describe the appearance of the caterpillar; notice its general worm-like form and absence of wings. In the head, observe the [Pg 363] small feelers, and watch the action of the mandibles in feeding. Behind the head come the three segments of the thorax; notice that each bears a pair of short, jointed legs. How many segments can you see in the abdomen? Which of the abdominal segments bear legs or feet? How do these differ from the thoracic legs? Look for the spiracles (p. 355) at the sides of the body. Which segments have spiracles? Kill a full-fed caterpillar by immersing it in methylated spirit, or by putting it into a small box with a few drops of ether (a most inflammable liquid) or chloroform. When it is dead, examine it more closely. Try to make out the mouth-parts clearly; they are best seen from the back of the head. The labium (p. 353) is here represented by a conical body called the spinneret, out of which come the silken threads used to protect the pupa. (c) The pupa.—When the larva is full-fed, it seeks out a sheltered place, and fixes itself in position by means of silk threads which issue from the spinneret; the larval skin is shed and replaced by a pupal skin, and the animal remains quiescent until the change from larva to butterfly is complete. Examine the manner of attachment of the pupa to its support. Kill a pupa by immersion in methylated spirit, or by dipping it for a moment in boiling water; carefully strip off the skin, and make a drawing of the animal. Especially notice the arrangement of the wings and legs.