A butterfly starts its life as a caterpillar, which hatches from an egg, eats voraciously and eventually sheds its skin to reveal a chrysalis. The chrysalis is a protective shell in which the caterpillar becomes a butterfly. By the time the butterfly emerges, or ecloses, it doesn't look much like it did when it formed the chrysalis. Its body has the same basic parts -- a head, a thorax and an abdomen -- but most of the similarities end there.
Along with its proboscis, a long, straw-like tube used for drinking, many of a butterfly's sensory organs are on its head. These include:
- Compound eyes, which are good at detecting color and nearby movement
- Moveable, segmented antennae, which have organs for detecting smells at the tips and structures for sensing the butterfly's direction and position at the base
- Labial palps at the base of the mouth parts, which help the butterfly decide what is and isn't food
Not all of a butterfly's sensory organs are located on its head, though. At the end of each of its six legs, all of which attach to its thorax, are taste organs that the butterfly uses to find food. When a butterfly's leg touches a good food source, a reflex causes its proboscis to uncoil. This lets the butterfly retrieve and swallow the food, which is digested in organs in the butterfly's abdomen. A butterfly's reproductive organs are located in its abdomen as well.
A butterfly's most dramatic anatomical features are its wings. They're made of an extremely thin, transparent material called chitin stretched over a series of vein-like structures. The forewings are closer to the butterfly's head and are roughly triangular. The hindwings are closer to the tail and are shaped like fans or seashells.
The colors and patterns come from layers of tiny scales. It's easy to think of these as similar to fish scales, but they're structured more like short, tiny hairs. These scales protect the wings and provide insulation. Typically, the scales on the top of a butterfly's wings are brightly colored, while the scales and the underside are patterned for camouflage.
At first, the wings are wet and wrinkled. The butterfly has to expand and dry them as soon as it emerges from the chrysalis. To do this, it uses its body as a pump and forces fluid through a series of tube-like veins. It's a little like inflating a balloon -- as the veins fill with fluid, they slowly stretch the surface of the wings.
This is just one of the things a butterfly has to do as soon as it emerges to prepare for its life of flight. The butterfly also must also get rid of the waste produced during its transformation and the remains of its last meal as a caterpillar. This waste is known as meconium, and it has a bright red, often bloody appearance. Then, the butterfly has to thoroughly clean all its sensory organs so it can find food. Finally, it has to get its proboscis in working order. When the butterfly emerges, its proboscis is in two separate pieces that join together with tiny hooks and fringes. The butterfly has to curl and twist the two halves of its proboscis to create one drinking tube.
All this work takes place before the butterfly even takes flight, and it doesn't end there. Next, we'll look at what it takes to keep moving and why cold temperatures can paralyze butterflies.