Butterfly and moth development: The caterpillar, or immature stage, has chewing mouthparts. Some caterpillars are serious pests of plants, stored food, and fabrics. (See Caterpillars for more information on caterpillars and their control.) Butterflies and moths lay their tiny eggs singly or in groups, usually on the plant or other food that the caterpillar eats. The eggs usually hatch in just a few days, although some are laid in the fall and do not hatch until warm spring weather arrives. The caterpillars emerge and immediately begin to eat and grow. They reach maturity after several weeks to several months, depending on the species, the abundance of food, and the temperature. Development is fastest in warm temperatures.

Pupation: At maturity, the caterpillars look for a place to pupate. The moth pupa is either enclosed in a silken cocoon or formed in some protected place such as within the plant itself, in debris on the soil surface, or buried in soil. The butterfly pupa, also called a chrysalis, is attached to a stem or some other support and usually is much more exposed than a moth pupa. At this stage a dramatic transformation takes place. Many of the internal organs, muscles, and nerves dissolve and the resulting fluids form new structures, producing a creature whose appearance and functions are entirely different. Some of the butterflies and moths emerge from their pupae in as little as 10 days; others spend the winter as pupae. The adult butterfly or moth emerges by splitting the pupal shell, spends several hours pumping fluid into its wings and hardening them, and then flies off. Male and female mate and the female then lays eggs. Butterflies and moths live a few days to several months. Some gardeners attract butterflies to their garden by providing the kinds of plants the caterpillars feed on, as well as plants that produce flowers that are particularly attractive to the adults. Good flowers to attract butterflies are butterfly bush (Buddleia), butterfly weed, lantana, thistles, tithonia, zinnia, and many herbs. Plants that are eaten by caterpillars of particularly pretty butterflies include milkweed, nettles, parsley, fennel, spicebush, and willow.