The Isabella Tiger Moth
or Woolly Bear

Teacher's Story

ANY times during autumn, the children find and bring in the very noticeable caterpillar which they call the "woolly bear." It seems to them a companion of the road and the sunshine; it usually seems in a hurry, and if the children know that it is thus hastening to secure some safe place in which to hide during the season of cold and snow, they are far more interested in its future fate. If the caterpillar is already curled up for the winter, it will "come to" if warmed in the hand or in the sunshine.

Woolly bears.  Photo by M. V. Slingerland.

The woolly bear is variable in appearance; sometimes there are five of the front segments black, four of the middle reddish brown, and three of the hind segments black. In others there are only four front segments black, six reddish ones, and two that are black at the end of the body; there are still other variations, so that each individual will tell its own story of color. There are really thirteen segments in this caterpillar, not counting the head; but the last two are so joined that probably the children will only count twelve. There are a regular number of tubercles on each side of each segment, and from each of these arises a little rosette of hairs; but the tubercles are packed so closely together, that it is difficult for the children to see how many rosettes there are on each side. While the body of the caterpillar looks as if it were covered with evenly clipped fur, there are usually a few longer hairs on the rear segment.

There is a pair of true legs on each of the three front segments which form the thorax, and there are four pairs of prolegs. All of the segments behind the front three, belong to the abdomen, and the prolegs are on the 3d, 4th, 5th and 6th abdominal segments; the prop-leg is at the rear end of the body. The true legs of this caterpillar have little claws, and are as shining as if encased in patent leather; but the prolegs and prop-leg are merely prolongations of the sides of the body to assist the insect in holding to the leaf. The yellow spot on either side of the first segment is a spiracle; this is an opening leading into the air tubes within the body, around which the blood flows and is thus purified. There are no spiracles on the second and third segments of the thorax, but eight of the abdominal segments have a spiracle on either side.

The woolly bear's head is polished black; its antennæ are two tiny, yellow projections which can easily be seen with the naked eye. The eyes are too small to be thus seen; because of its minute eyes, the woolly bear cannot see very far and, therefore, it is obliged to feel its way. It does this by stretching out the front end of the body and reaching in every direction, to observe if there is anything to cling to in its neighborhood. When we try to seize the woolly bear, it rolls up in a little ball, and the hairs are so elastic that we take it up with great difficulty. These hairs are a protection from the attacks of birds which do not like bristles for food; and when the caterpillar is safely rolled up, the bird sees only a little bundle of bristles and lets it alone. The woolly bear feeds upon many plants, grass, clover, dandelion and others. It does not eat very much after we find it in autumn, because its growth is completed. The woolly bear should be kept in a box which should be placed out of doors, so that it may be protected from storms but have the ordinary winter temperature. Keeping it in a warm room during the winter often proves fatal.

Normally, the woolly bear does not make its cocoon until April or May. It finds some secluded spot in the fall, and there curls up in safety for the long winter nap; when the warm weather comes in the spring, it makes its cocoon by spinning silk about itself; in this silk are woven the hairs which it sheds easily at that time, and the whole cocoon seems made of felt. It seems amazing that such a large caterpillar can spin about itself and squeeze itself into such a small cocoon; and it is quite as amazing to see the smooth little pupa within the cocoon, in which is condensed all that was essential of the caterpillar. Sometimes when the caterpillars are kept in a warm room, they make their cocoons in the fall, but this is not natural.

The cocoon of the woolly bear.  Photo by M. V. Slingerland.

The issuing of the moth from the cocoon is an interesting lesson for the last of May. The size of the moth which comes from the cocoon is quite comparable as a miracle with the size of the caterpillar that went into it. The moth is in color dull, grayish, tawny yellow with a few black dots on the wings; sometimes the hind wings are tinted with dull orange-red. On the middle of the back of the moth's body there is a row of six black dots; and on each side of the body is a similar row. The legs are reddish above and tipped with black. The antennæ are small and inconspicuous. The moths are night fliers, and the mother moth seeks some plant on which to lay her eggs, that will be suitable food for the little caterpillar as soon as it is hatched.

References—Moths and Butterflies, Ballard.

The Isabella tiger-moths, the adults of the woolly bear. The larger is the female.  Photo by M. V. Slingerland.

Method—Have the children bring in woolly bears as they find them, place them in boxes or breeding jars which have grass or clover growing in them. The children can handle the caterpillars while they are studying them, and then they should be put back into the breeding jars and be set out of doors where they can have natural conditions; thus the entire history may be studied.

2. Look closely at the hairs of the woolly bear. Are they set separately or in rosettes? Are any of the hairs of the body longer than others or are they all even?

3. Can you see, just back of the head, the true legs with their little sharp claws? How many are there?

4. Can you see the fleshy legs along the sides of the body? How many are there of these?

5. Can you see the prop-leg, or the hindmost leg of all? Of what use to the caterpillar are these fleshy legs?

6. Describe the woolly bear's head. How does it act when eating?

7. Can you see a small, bright yellow spot on each side of the segment just behind the head? What do you suppose this is? Can you see little openings along each side of all the segments of the body, except the second and third? What are they? Describe how the woolly bear breathes.

8. On what does the woolly bear feed? If you can find a little woolly bear, give it fresh grass to eat and see how it grows. Why does it shed its skin?

9. When the woolly bear is hurrying along, does it lift its head and the front end of its body now and then? Why does it do this? Do you think it can see far?

10. What does the woolly bear do when you try to pick it up? Do you find you can pick it up easily? Do you think that these stiff hairs protect the woolly bear from its enemies? What are its enemies?

11. Where should the woolly bear be kept in winter to make it comfortable?

3. What happens to it inside the cocoon?

4. Cut open a cocoon and describe how the woolly bear looks now.

3. What is the color of the moth and how is it marked? Are the front and hind wings the same color?

4. What are the markings and colors of the body? Of the legs?

5. What do you think that the Mother Isabella will do, if you give her liberty?