I must admit, I felt very bad. I knew so little about caterpillars and butterflies. In order to fill in this shameful gap and to help Odius H., I went to the forest library.


A butterfly is an insect. Insects are by far the largest group of organisms on Earth. Scientists have discovered more than 700,000 insect species. They know many more exist, primarily in tropical regions. Insects fall into four major groups. One of them is Lepidoptera, which means "scaled winged." This group includes butterflies and moths. Dustlike scales coat the wings, bodies, and legs of moths and butterflies. That is how the group got its name. Unlike moths, butterflies usually have bright or striking colors. They are active during the day. The most distinctive features of butterflies are their antennae and the way they hold their wings up when they rest. Around 120,000 known types of Lepidoptera extend to all parts of the world.

Did You Know?
An insect is an arthropod. That’s an animal with a spinal column down its back, an outer skeleton, and a body in segments. As an adult, an insect has three pairs of legs and usually two pairs of wings. It also has a body with a head, thorax, and abdomen.

The Four Faces of Lepidoptera

Most insects have a complicated life cycle. This group is no exception. There are four basic stages in a butterfly’s life. Scientists call this its life history.

1. Egg
In the beginning, the male fertilizes eggs inside the body of the female. A shell protects the eggs. The female places the eggs on the leaves of a specific plant. She attaches them using an adhesive. Her choice of plant is very important. It can make the difference between life and death for the butterfly.

2. Larva/Caterpillar
The egg produces a larva. A caterpillar is the larva stage of a butterfly. It has no wings and looks like a worm. Its role in life is to eat in order to grow. Strong jaws chew the food, and a long body aids in digestion. It also produces silk threads. They “glue” the caterpillar to the underside of leaves. They also help it escape from enemies. Producing a thread, the caterpillar can jump freefall from its leaf and dangle until the danger goes away. Caterpillars have three pairs of "true" legs—legs that look like legs—and several prolegs. The prolegs help the caterpillar attach to surfaces.

Did You Know?
As it grows, a caterpillar sheds its "skin" several times. This is called molting. Instar is the stage between molts. Each instar may be quite different from earlier ones.

3. Pupa
During the pupa stage, the caterpillar turns into a butterfly. A capsule known as a chrysalis protects the new form. Even so, the pupa is helpless against predators. Predators are animals that might kill it for food.

Some experts call this the "resting stage" of the life cycle. It is anything but restful! First, special chemicals break down the caterpillar’s body. The body parts then change into an adult butterfly. This process is metamorphosis. It can take from a week to a month or more. When the butterfly is fully developed, the capsule opens. An adult emerges. The adult hangs from the capsule. It expands its wings to let them dry. Then it flies away.

4. Butterfly
Only the butterfly is able to fly and to reproduce. The adult has three main parts. The head contains the organs for seeing, hearing/smelling, and eating. The thorax contains muscles and internal body parts. The abdomen controls digesting food and reproducing.

Did You Know?
All creatures in a forest work together with their environment. They work in different ways. One way is by competition. One animal might compete with another for its requirements for survival. These include water, food, and shelter. Butterflies and caterpillars are two independent forms of the same animal. Why don’t they compete with each other? Each lives in a different place and eats different foods. With no competition between the two forms, the chance of survival for each form increases.


A butterfly egg has a very small chance of becoming an adult. Every stage of the life cycle carries risk. There might not be enough host plants. The eggs might not get enough moisture during a dry spell. The capsule might fall. Deadly life forms inside a caterpillar might kill it. Birds might swoop down and have a butterfly for lunch. 

Odius H.’s biggest enemy was the tachinid fly. This fly is a parasitoid. It lives off a host animal and eventually kills it. This is what happens: The fly lays eggs on the caterpillar or on the leaves it eats. Once inside the “host,” each egg becomes a maggot. A maggot is the larva stage of a fly. Remember, a fly is also an insect, with the life stages of an insect. The maggot feeds on the inside of the caterpillar until it is ready to start its pupa stage. Then it cuts through the body wall and becomes a pupa in the ground. This process means death for the host.

Did You Know?
The wings of butterflies have beautiful colors and patterns. This beauty has a purpose. Some wings help the butterfly blend into its surroundings. For this reason, the undersides of Odius H.’s wings resembled dead leaves. Other wings resemble something the predator avoids. Both patterns help the butterfly survive in the forest.


Odius H. was not dreaming about becoming a nymph. He was dreaming about becoming a nymphalid, and he became one. This is a large group of butterflies with certain features in common. They live throughout the world and include such popular butterflies as the monarchs, zebras, and painted ladies.

Did You Know?
Birds were not the first animals to fly. Insects were. They flew for 100 million years before flying reptiles appeared. Insect wings developed from sacs on the central body wall. Adult wings are made strong by a network of tubes called veins. These veins carry air, not blood.

Historis odius

  • It lives in tropical forests from the southern United States to Argentina.  A man named Fabricius discovered it in 1775. 
  • Its nickname is the stinky leaf wings butterfly. In Spanish, its common name is pescadito (little fish). When something disturbs the capsule, it wriggles like a fish out of water.
  • This caterpiller feeds on only one plant, the Cecropia.
  • When conditions are good, adult butterflies can live up to six months or more. This is long for an insect. Unfortunately, conditions in El Yunque aren’t good.
  • The butterfly is a remarkable flyer. It can fly for a long time at high speeds.
  • The main threat to its life comes from flies. (See the Survival section.) Though lizards eat caterpillars, they don’t seem to eat this one. Apparently, they don’t like the spines.