To supplement the study of the imprisoned caterpillars, study should be made at the same time of the insects out of doors and under natural conditions. If none appear upon an apple or wild cherry tree near the school-house, the teacher should transfer a colony to such a tree (Fig. 148). This may be done by fastening a twig with an egg-mass upon it to a branch of the tree. If too late to get the unhatched eggs, get a nest with the small worms in it and tie that to the convenient branch instead. This study of the insects out of doors is very necessary in discovering their normal habits. LESSON II. THE CATERPILLARS. FIG. 149, _c_. If the eggs hatch before the leaves appear, upon what do the caterpillars feed? How long is it after hatching before the caterpillars commence to make their tent? Where is the tent always formed? _Answer._ In the fork of the branches. Why is this so? _Answer._ The forking branches offer a convenient support upon which to stretch the tent: and when, as in the case out of doors, the tent is spread in a fork of the larger limbs, these limbs afford two branching roads for the caterpillars to follow in searching for food. Let the pupils make drawings of the tent as soon as it is large enough to be seen well. What is the color of the caterpillars when they are a week old? Upon what do they feed? At what time of day do they feed? When on a tree, how far from their tent do they go for food? Are the paths over which the caterpillars travel when searching for food marked in any way? [Illustration: _Fig. 148. A young colony of tent-makers on a cherry tree._] _Answer._ This caterpillar spins a silken thread wherever it goes and therefore leaves a trail of silk behind it. Of what is the tent made? Compare the tent with a spider's web and note the differences. Where does the silk come from, of which the tent is made? _Answer._ The silk glands of the caterpillar are situated near the mouth, while those of the spider are on the rear end of the body. LESSON III. HOW THE INSECTS GROW. The caterpillars shed their skins about five times. The first molt occurs about three days after they hatch; the second molt about four days later; and the third molt about six days after the second. After each molt, the color and markings of the caterpillars are somewhat changed. During some of the molts the pupils should watch a caterpillar change his skin. After the class has seen this operation the teacher may give the following lesson: Where is your skeleton? What is it made of? What is it for? Bring out the fact that the skeleton is a support for the muscles and organs of the body. Where is an insect's skeleton? Get as many answers to this question as possible, then explain: