Butterflies & Moths

Most people really enjoy butterflies flitting through the garden. And what would a summer evening be without an occasional moth?

Gulf fritillary

Generally speaking, these beneficial insects improve pollination and they are a sign of a healthy environment. Moths and butterflies (and their caterpillars) are prey animals to many predators, such as bats, birds, and lizards. The presence of butterflies and moths indicates a healthy level of biodiversity that translates into a healthier garden. The plight of the Monarch butterfly is a well known indicator of environmental problems.

​Differences between butterflies and moths

The jury is still out on the exact difference between butterflies and moths. Skippers and butterfly moths muddy the taxonomic waters, but there are some clear differences (with several exceptions):

• Moths have many different ancestors; all butterflies are descended from a single species.
• Butterflies have thin antennae with small knobs at the end; moths lack the club end.
• Most butterflies are brightly colored while moths tend to be gray, brown, black or white.
• Butterflies tend to be thin and smooth bodied; moths are usually fatter and often fuzzy.
• Moths use scent to find a mate (up to 7 miles away!); butterflies rely on sight to find a mate.
• Most moths are active more at night; butterflies are active during the day.
• Moths have ears and butterflies do not.
• Moths usually rest with wings spread out; butterflies often fold their wings above their back.
• Butterflies use a proboscis (sucking tongue) to drink nectar; most moths do not eat. (The male Luna moth doesn’t even have a mouth!)

Head of a leaf miner moth showing the extent of scales on the head (Louis Howard) Public Domain

​Lifecycle of butterflies and moths

In spite of the differences, butterflies and moths share the same basic 4-stage life cycle. Moths and butterflies start out as eggs, which hatch into caterpillars. These caterpillars are what cause most of the damage to garden plants. Caterpillars are voracious eaters! After they fatten up on garden plants, moth caterpillars spin a cocoon around themselves, while butterfly caterpillars form a chrysalis. Inside these tidy little protective packages, caterpillars are transformed into insects of the sky. [I just learned, watching BBC, that the Arctic Wooly Bear caterpillar may take 14 years to complete its metamorphosis and that it can survive being frozen solid!]

Comparison of moth and butterfly dorsal anatomy (Mrice20) CC BY-SA 4.0

Moth and butterfly identification

A student at the University of Washington created a lovely animation of 42 North American butterflies. You can see it here. This is an excellent resource because it also shows range maps! Another great interactive tool can be found at Butterflies and Moths of North America.

Damage caused by butterflies and moths

While moths and butterflies won’t damage your plants, their caterpillars certainly will. This is especially true for the imported cabbageworm. During summer months, monitor plants for feeding holes, frass, and rolled or webbed leaves. Since moth and butterfly caterpillars are food to so many other critters, handpicking is the best treatment. Adding pesticides simply disrupts the natural controls already in place.