Smithsonian photo by Kjell B. Sandved. Numbers of species. Due to their bright colors and visits to flowers, butterflies are the most familiar of insects to humans. There are about 17,500 species of butterflies in the world, and around 750 species in the United States. They differ from other insects also by their ability to coil up their proboscis.
Caterpillars are the names given to the larvae of both butterflies and moths.
They are usually very distinctive, and in some cases may be identified more easily than the adults. When they are developing, their skin may be shed four or more times, with each molt often changing the coloration and appearance of the caterpillar. They eat voraciously to transform plant material into tissues that they will need for metamorphosis. Butterflies are commonly associated with plants, and the relationship is sometimes complex. Immatures, with few exceptions, eat plants, and therefore may be considered harmful to the plants.