Butterfly Or Moth?
How to tell the difference.
Copyright 2019 - Linda L. Rigsbee
Illustrated by Linda Rigsbee
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Worldwide, there are nearly 180,000 species in the Lepidoptera family of butterflies and moths. About 160,000 of those are moths and only about 17,500 are butterflies. Moths outnumber butterflies about 10 to 1. So, how do you determine whether that beautiful insect fluttering around your yard is a butterfly or a moth?
While there are exceptions to every rule, there are some basic differences that begin very early in the life cycle. This booklet will explore some confusing terms and replace them with facts.
The intent of this booklet is to get the reader interested enough to explore further. There are many books that go into detail about the different species; their habits and habitats. This booklet is a launching pad for exploration.

Linda L. Rigsbee, Author

Caterpillars, worms, butterflies, moths; it gets confusing, doesn’t it? No worries. This booklet will straighten things out in a jiffy.
We can start by eliminating one term here – the worm. A worm is a worm. It has no eyes or legs and it stays a worm its entire life.
Pretty simple, yes? You’d think so, but the terms we use confuse the issue. For example: what, exactly, is a grub worm? Here’s a hint. It has legs. You guessed it. It isn’t a worm at all. Neither is an inch worm or a hornworm. If it has legs, it is a larva. A larva will become something else in its life cycle. A worm will always be a worm.
A grub worm is a beetle larva. It spends its larva life in the ground in a 3-year cycle. Below is a drawing showing the difference between a worm, a beetle larva and a caterpillar.

A caterpillar is not a worm. A caterpillar begins its life as a larva, becomes a pupa and ends its life as either a moth or a butterfly. So, what is the difference between a moth and a butterfly?
The line gets as fuzzy as a wooly bear caterpillar at times, but there are some basic differences. Both are in the family Lepidoptera, but there are some anatomical differences.

1. Antennae:
A moth has feathery or ragged edged antennae. Butterfly Antennae are long shafts with a bulb at the end. Butterflies and moths “smell” with their antennae and feet. Some moths can detect their prospective mate or food as much as seven miles away!

2. Wings

When resting, butterflies fold their wings vertically – up over their backs. Moths hold their wings down, usually hiding their abdomen. Moths are usually smaller than a butterfly, but not always. The largest moth has a wing span of 12 inches, and the largest butterfly wingspan is 11 inches. More about this later.

3. Pupa Stage

After feeding for a few weeks, caterpillars attach themselves to something and pupate. They go into a stage where they metamorphosize into an adult – a butterfly or a moth.
The butterfly caterpillar hangs upside down in a J shape, usually attaching itself to a limb. It then sheds its outer skin and a hard, smooth shell called a chrysalis forms around it.
The moth caterpillar builds a cocoon, wrapping itself in a silk covering. It is soft and silky. Sometimes they wrap themselves in a leaf, stuck together with silk.

4. Anatomy

If you have good eyes or a magnifying glass, you can identify a moth by its frenulum. Butterflies don’t have a frenulum. A frenulum is a piece of tissue that attaches the forewing to the hind wing so that both wings work together when they fly. The frenulum couples with the retinaculum on the upper wing in many species.
Moths also tend to have thicker and fuzzier bodies. Their feathery antennae have more sensors than the butterfly – which leads us to number 5.

5. Habits
Moths are primarily nocturnal – they fly during the night, like a bat. They even have a kind of radar through their intricate and sensitive antennae.
Butterflies are primarily diurnal – they fly during the day. Some butterflies and moths are crepuscular – they fly at dawn and dusk.
Both butterflies and moths are pollinators, though the moth is better at it because of its shorter legs and fuzzy body that tend to pick up more pollen.
Butterflies and moths do not eat plants. They drink nectar from the flowers. However, they do lay eggs on the plants and their caterpillar offspring do eat plants. Many are plant specific. For instance, the Monarch caterpillar only eats milkweed.

The Lepidoptera Family

The largest butterfly species in the world is the Queen Alexandra Birdwing found in the rain forests of Papua New Guinea. Its wingspan is 11inches. The smallest are the Pygmy Blues, which are native to North America, though they can be found in places as far away as Saudi Arabia and Hawaii. They have a wingspan of ¼ to ½ inches.

The largest moth species in the world is the Atlas, with a wing span of 12 inches. It lives in Southeast Asia. The smallest is the Stigmella Maya moth, with a wingspan of a mere 3/32 inch. It lives on the Yucatán Peninsula of southeastern Mexico.
The most common butterfly in the US is the Cabbage White. The most common moth is the Tomato Hornworm moth.
Interesting Facts

The tiger moth produces an ultrasonic clicking sound that jams bat sonar. This is a defense against predators.

The Luna moth has no mouth! It never eats. It only lives about a week – long enough to mate and lay eggs.

Butterflies and moths have a liquid only diet. They suck up nectar through their proboscis, which is like a straw.

When a butterfly emerges from its chrysalis, its proboscis is in two pieces. The butterfly must assemble it!

Butterflies cannot fly when the temperature gets below 55 degrees F.

Author’s note:

The Lepidoptera family is full of interesting facts. Hopefully, this booklet has inspired you to delve deeper into their family tree and become more familiar with them. You might even become a lepidopterist (someone who studies the Lepidoptera family.)

Linda L. Rigsbee, Author

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