NABA Eugene – Springfield
North American Butterfly Association, Lane County Chapter
What is a butterfly?
Butterflies are a type of insect that, in its adult form, flies in the daytime, has clubbed antennae and has scaled wings that are often brightly colored.
Butterfly vs Moth
Butterflies and moths are both contained within the large order of insects called Lepidoptera. An order is simply a classification for a large group of related species. Out of some 170,000 Lepidoptera species worldwide, about 17,000 are butterflies, while the rest are moths. Lepidoptera means scaly-winged, as both butterflies and moths have scaled wings. Nearly all butterflies fly during the day, but some moths also fly in the daytime. Most butterflies are brightly colored, but many moths are also very brightly colored. So, how do you distinguish the two? The best way is to look at the antennae. On butterflies, the antennae are almost always long and thin with “clubs” at the end. Moth antennae are almost never long and thin with clubbed ends. There are exceptions on both sides, but they are so obscure that you’ll probably never see them.
Butterfly Life Cycle
Butterflies go through four separate life stages: the egg stage, the larva stage, the pupa stage, and the adult stage. The length and timing of each stage differs from species to species. The radical change in the butterfly’s appearance, structure and activities from caterpillar to adult butterfly is known as metamorphosis.
The first stage is the egg stage. The female butterfly lays its eggs singly or in clusters on or near the plants which the caterpillar will use as food. In many buttefly species, the caterpillar can only feed on one or two plant species, so the female is very particular about which plant she lays her eggs on. Eggs for different species come in many colors, sizes and shapes. The eggs are laid on the undersides of leaves, on stems, and in some species on old logs or stumps. The eggs of certain butterflies hatch in a few days or weeks, but others may require months to hatch.
The larval stage follows the egg stage, as the caterpillar emerges from its egg. Caterpillars vary among species as much from each other as their adult forms do. Some are hairless and smooth, while others have a thick coat of hairs of many different colors. Some have spines or long whiskers. Caterpillars are vulnerable to predation by birds and other animals, and have evolved with hairs, spines, or other characteristics as defense mechanisms. As it grows, a caterpillar will shed its skin, or molt, several times as it grows, to accommodate its larger size, much like a snake sheds its skin as it grows. Each occurrence of skin-shedding is called an instar. Most caterpillars undergo four or five instars before they are full-grown.
The third stage in the life of a butterfly is the pupa stage. Instead of spinning a coccoon out of silky threads as many moths do, most butterflies will simply fasten themselves to sticks or leaves with a few threads of silk. After attaching itself, the caterpillar sheds its skin for the last time, the pupa (rather than another, larger version of the caterpillar) emerges and then its skin begins to harden. The pupa has no eyes, antennae, mouth, wings, or legs. In nearly all species, the pupa moves very little, except perhaps to wiggle its abdomen slightly.
The skins of many kinds of butterfly pupae are dull and difficult to see, while others are bright and shiny or clear green, with small golden spots (as in the monarch). Regardless of their color, the pupa at this stage is called a chrysalis. Within the hardened case of the chrysalis, many changes occur. The entire body of the caterpillar turns into a soft, creamy liquid, out of which the wings, legs, and other body parts of the adult butterfly are slowly formed. It is not known exactly how this process occurs. The insect may remain in this form for a few weeks or several months, depending on the species of butterfly and the time of year. Some species remain in this form throughout the winter.
In the fourth and final stage, the shell of the chyrsalis splits, and a full-grown insect, emerges, weak and heavy with moisture. It’s abdomen is large, and the wings are damp and crumpled. The butterfly crawls to a twig or other resting place, hangs its head downward, and waves its wings rapidly. Gradually the wings unfold, expanding as the fluids of the body flow into the veins in the wings. The abdomen becomes smaller as it is emptied of some of its fluids. Once the wings are fully expanded, the butterfly will bask in a sunny spot to dry its wings out until they are stiff and light enough for flight.
Once the butterfly’s wings are fully dry it is fully grown, and ready to fly. Whether it is large or small, it will grow no further. In the adult butterfly stage, it will live from a few days to many months depending upon the species. The male and female mate in order to fertilize the eggs, and the female flies off to lay its eggs. The average life span of adult butterflies is about two weeks. So, in most species, the adult butterflies die within days of mating or egg-laying.