Moths and butterflies together make up one of the largest groups of animals – at least 160,000 species worldwide. Only 1 in 10 of these is what we call a butterfly; the other 90% we call moths. Although there are exceptions, most moths are nocturnal and therefore drab, and many are very small; butterflies are day-fliers, colorful, graceful in flight and often fairly large. Compare moths to butterflies, certainly the most charismatic of our Garden insects, and the former don’t stand a chance in a popularity contest. And yet, entomologists consider butterflies as essentially representing a lineage of “brightly-colored day-flying moths.” Evolutionarily speaking, butterflies are really … moths!

Probably the easiest and most reliable characteristic that distinguishes adult butterflies from moths are the antennae: butterfly antennae are long and thin with a club (or hook) at the end; moth antennae are more variable, and can be straight or sometimes very feathery, but without a club.

Habits and ecological importance

With very few exceptions (think: clothes moth), butterfly and moth larvae (caterpillars) are plant-feeders, chewing their way through leaves, stems, roots, flowers or seeds. The vast majority of species specialize on one or a very few closely related host plants. Some important examples in the Garden are Aristolochia californica (California Pipevine) and Battus philenor hirsuta (California Pipevine Swallowtail) and Asclepias speciosa (Showy milkweed) and  Danaus plexippus (Monarch).

The moth pupa (the stage between caterpillar and adult) takes cover underground, in a leaf shelter, or in a silk cocoon. The butterfly pupa (chrysalis) is hard-shelled, often colorful and attaches to a plant or other outdoor surface.

Adult moths and butterflies feed mostly on nectar with a long tongue (proboscis) that they keep compactly coiled when not feeding. Unlike their caterpillar stages, they tend not to specialize on particular plant groups, but may have preferred flowers. As pollinators, butterflies are not generally very efficient; while moths are considered important pollinators, especially of night-blooming plants. Some moths, such as yucca moths, have formed very specific pollinating/host plant associations with particular plants.

Because of their diversity and abundance, moths (including butterflies) are among the most important insect groups on Earth. They and their caterpillars are thought to transfer more energy from plants to other organisms than any other kind of herbivore. This makes them ecologically indispensable, across many habitats. For gardeners, including caterpillar host plants – mostly natives – has become an essential part of the “habitat garden.”

For photos and more detailed information about butterflies in particular, see Butterflies in the Garden.