Caterpillars have a considerable effect on the types and numbers of plants in tropical rain forests. They also can be serious pests on banana plantations. They may eat more leaves than all the other insects around. The role of a caterpillar is to feed and grow until the insect is ready to form a cocoon and turn into a butterfly or moth. Many other animals depend on caterpillars for their food.
In spite of how important these creatures are to the forest, very little is known about their life cycles. When Dr. Lee Dyer and Dr. Grant Gentry began this project, they did not know what type of butterfly or moth some of the caterpillars would turn into.
For a butterfly or moth, there are four very distinct life stages: egg, caterpillar, pupa (cocoon), and adult. At each stage the body is very different.
Today we were able to watch a butterfly actually laying her eggs on top of a leaf. Once the eggs hatch, they become caterpillars. Most will molt several times as they increase in size and outgrow their outer covering. Finally, the caterpillar will pupate (form a cocoon). While it is in the cocoon, its entire body reorganizes itself. When the body finally emerges, it is an adult butterfly or moth.
Caterpillars have the same three basic body parts of an adult insect: head, thorax, and abdomen. Their heads have six segments, with mandibles or mouthparts for feeding and antennae as well as primitive eyes. Some have horns. Other species have tiny hairs, or setae, on their heads. The thorax, or middle section, has three segments, each with a pair of legs. The abdomen has ten segments, some with tiny leg-like structures that act like Velcro to help the caterpillar stick to the leaf surface.
Lee and Grant have found many different species of caterpillars in the rain forest. Their goal is to document the life histories. You can find pictures and information about the caterpillars they have collected at www.caterpillars.org.
Photos courtesy of Shauneen Giudice/Earthwatch Institute