To assist students in identifying the caterpillars' body parts and finding evidence for the function of each.

To help children learn to make clear and detailed descriptions of monarch attributes and behavior.

To encourage students to record evidence of growth and change by observing a monarch at different stages and drawing a series of pictures to represent what they see.

Six tiny caterpillars were placed in separate petri dishes on the counter. Each dish also contained a piece of fresh milkweed leaf. Caterpillars were generally found on the softer underside of the leaves. In two petri dishes we placed a penny under part of the leaf, so children could compare the size of something familiar to the size of the caterpillar. At first, the caterpillars were difficult to see with the naked eye. We set up a video flex camera to magnify the image of the tiny caterpillars and allow students to observe the organisms, their structures and their behavior. Under high magnification, the children could compare the caterpillar size to the penny size to understand how much the image was enlarged.

• Lesson One: What do you see?

• Lesson Two: What do you see? Part 2

• Lesson Three: What do we know about our caterpillars?

• Summary

In order to find a shared way of knowing and talking about the caterpillars, it was important that children verbalize about what they saw. Initially, students described and identified surface features such as color, stripes, body parts, and the comparative size of the caterpillars. Towards the end of our observations, children were looking for ways to quantify changes, explain the function of different structures, and give reasons for certain observable behaviors.

At first, children described the size of the caterpillars mainly in terms of length by using terms such as tiny or little. As they watched the caterpillars grow, they compared the size of the caterpillar to the penny. Since the size of the penny was a constant, it provided a reference for talking about the length. They also "measured" growth by approximating the size of the caterpillar to the demarcations on a centimeter strip that was placed in the dish. Towards the end, many children also used terms such as longer, bigger, fatter and even humungous to share ideas about the length and width or perhaps even volume of the organism.

As the caterpillars grew, their rate of consumption increased. Durning the first week, students noted that there were tiny pinholes eaten into the middle of the milkweed leaf. Later, children noticed that the caterpillars were not only eating much more food, but they were eating the leaves faster. By week three, the caterpillars were eating one or two leaves each day, and they ate the leaves from edge to edge leaving nothing uneaten. Frass collected in the bottom of the petri dish, and children also compared the size of the older frass which was smaller, to the more recent frass. Children tended to measure the rate of consumption by describing how much leaf had disappeared and in what part of a day.

Antenna like structures developed on the monarch's back. At first, children noticed the tiny nubs on the day old caterpillar. By the next observation, the nubs in front had developed into what looked like antenna, and nubs were just starting to appear at the other end of the caterpillar. Children made predictions that those nubs would also turn into antenna, and they began to speculate about the function of both sets of antenna. The pair near the head were longer than the pair at the other end. Children wondered whether the caterpillar used them for defense to scare other predators away, or as camouflage. Some children thought that maybe the caterpillar used them to sense or feel things.

The color and the pattern of stripes changed as well. When the caterpillars were one day old, children drew a diagram in their journals to record that they saw a clear band and a dark band repeated on the caterpillar's skin. As the caterpillars grew, the colors changed to black, yellow and white. Children noted that the pattern also changed from dark, clear, dark, clear, dark, clear... to black, white, black, yellow, black, yellow, black, white, black, yellow, black, yellow .