Tom Turpin
Professor of
Purdue University


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Flies in the face of fashion

What's Buggin You Now?





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Is It a Moth or Is It a Butterfly?

Monarch butterfly

Butterflies and moths are some of the most recognizable adult insects. They are common, and many have large wings covered with scales. The scales come off easily when the insect is touched. These scales are the basis for the word Lepidoptera - literally, scale wing. Lepidoptera is also the name of the insect order in which butterflies and moths are classified.

Scaly wings aren't the only characteristic that butterflies and moths have in common. Both types of insects have a mouth called a proboscis. A proboscis is a coiled tube that functions much like a party blower. The proboscis is extended to allow the insect to suck up liquids, such as nectar or water.

Western bean cutworm moth photo credit: Marlin Rice

Moths and butterflies possess fairly large eyes, with many lenses in each eye.
Both types of insects exhibit complete metamorphosis, meaning they have four life stages: egg, larva, pupa and adult. Both butterfly and moth larvae are called caterpillars.

Caterpillars have a well-developed head and a cylindrical body, which is made up of 13 segments. Each of the three segments behind the head has a pair of legs, just like adult insects. But caterpillars also have some additional, fleshy, leg-like appendages - called prolegs - on other segments. Prolegs have tiny hooks at the end that function to grasp things such as the stems and leaves of plants. That is also why caterpillars can cling to your finger if you pick one up.

Another characteristic of Lepidoptera that caterpillars possess is silk glands. These glands are modified salivary glands and are found in the caterpillar's mouth. Caterpillars sometimes use silk they produce to spin a cocoon. The best known of the cocoon spinners is the appropriately named silkworm. Silk is also used to tie leaves together to form a shelter, as tent caterpillars do. For others, silk becomes a line on which to suspend themselves from the limb of a tree.

So scales, large compound eyes, a coiled proboscis and larval forms called caterpillars are shared characteristics of Lepidoptera. But how do moths differ from butterflies? Butterflies have knobbed antennae; moths' antennae lack a knob and are generally fuzzy. Butterflies fly during daylight and most, but not all, moths are active only at night. Bodies of butterflies tend to be slender while the bodies of moths are likely to be stout.

There are some other differences between butterflies and moths as well. In general, butterflies, as a group, are brighter-colored than moths. That is because all butterflies fly during the day when colors can be seen. Moths tend to be dull-colored because they want to hide during the day, when they are not active. A few moths fly during daylight hours and, like butterflies, many of them exhibit bright colors.

How living butterflies and moths hold their wings is another clue as to which is which. When at rest, butterflies position their wings straight up over their body or straight out to the side. Moths fold their wings back over their abdomens.

Some moth caterpillars can be described as fuzzy. One such fuzzy fellow is called the woolybear caterpillar and has become famous as a predictor of winter severity. Not all moth caterpillars are fuzzy, but no butterfly caterpillars would be described as fuzzy.

There are also some general differences between the pupae of butterflies and moths. Moth pupae tend to be smooth and brown in color. Butterfly pupae are often brighter colored; many are sculptured and are called chrysalids. In general, moth pupae are encased in a cocoon. But not all. Some moths, such as adults of the well-known tomato hornworms, are examples. When a hornworm caterpillar stops feeding on tomato plants, it crawls into the soil and forms a pupation chamber. Here, it transforms into a pupa without forming a cocoon.

So deciding if a scale-winged insect is a moth or butterfly is not always an easy thing to do. But if it is flying during the day, has knobbed antennae and rests with wings straight up or out to the sides, it is a butterfly. If it is flying at night or is at rest with wings folded over the back, it is a moth. Otherwise, to be safe, you can always say something like, "Wow, look at that Lepidopteran!"



Writer: Tom Turpin
Editor: Olivia Maddox