Are butterflies your favorite insects? Graceful, non-threatening, mysterious and, above all, beautiful — what’s not to like! Butterflies get most of our attention because they’re flashier and fly by day. Moths, mostly inconspicuous creatures of the night, go largely unnoticed by us (until we stand under a porch light!).
Butterflies, along with moths, belong to the order Lepidoptera (Lep-uh-DOP-ter-uh).The name comes from the Greek libido, meaning scaly and ptera, meaning wings. The origin of the name “butterfly,” isn’t known, but it dates prior to the 8th century and was originally a combination of the Old English words butere (butter) and fleoge (fly). Butterflies aren’t “flies,” but they do fly, so maybe that part of their name is fitting, but how did butter find its way there? There are several theories. One of the most common is that a particular group of butterflies, called sulphurs, were called “butter-colored flies” back then. Eventually, they all became butterflies regardless of color. Another is that butterflies were thought to steal milk or butter and earned their name that way. As for moths, their name comes from Scandinavian mott, for maggot, perhaps a reference to the caterpillars of moths.
Lepidoptera is a large order of insects, second only to beetles in the number of species that have thus far been described by entomologists. Recently examined fossilized scales from a moth’s wing found in Germany show that moths, at least, have been around for 200 million years (the early Jurassic Period).
Butterflies and moths inhabit nearly every region of the world, including the Arctic. There are about 17,500 species of butterflies and 160,000 species of moths around the world. In the continental U.S., there are around 11,000 species of moths and 750 species of butterflies.¹
Butterflies and moths are an important food source for other animals. They’re also pollinators because the winged adults spread pollen while moving from flower to flower. From the perspective of farmers, gardeners, arborists and other affected parties, they’re also destructive — their caterpillars destroy crops, and some destructive moth caterpillars threaten the entire existence of some of our favorite trees.
Butterflies range in size from the 0.5 – 0.8 inch (12 – 20 mm) wingspan of the Western Pygmy Blue Brephidium exilis), found in the southern U.S., to the 12-inch (30 cm) wingspan of the Queen Alexandra’s Birdwing (Ornithoptera alexandrae), a Papua New Guinea rainforest species.
Moths fill a range of sizes, too, from the tiny Nepticulid moth with a wingspan of 1/16-inch (1.6 mm) up to the Atlas Moth (Attacus atlas) of Southeast Asia, which has a 12-inch (30 cm) wingspan.
The order Lepidoptera consists of two basic groups: (1) moths; and (2) butterflies and skippers. To the unpracticed eye, all may seem much alike. But, you can quickly learn to discern a moth from a butterfly from a skipper. Exceptions do exist, but they’re relatively few and you can count on the following to be reliable most of the time.
(To make the text a little less wordy, from hereon the word “butterfly” will mean butterflies, skippers and moths, except where differences are noted.)
Difference between butterflies, skippers, moths at a glance
|Antennae clubbed tip||Antennae clubbed and hooked||Antennae never clubbed nor hooked|
|Usually brightly colored||Usually dull orange, tan, gold or brown||Usually drab: brown, gray, black, white or combination. Wings often camouflage pattern|
|Active in daytime||Active in daytime||Active at night|
|At rest, wings usually held upright and together||At rest, forewings upright and together; hindwings held horizontally||At rest, wings held flat out to the sides or folded atop the body|
|Body smooth, slender||Body stout||Body plump, hairy or funny-looking|
Butterflies have three main body parts — head, thorax and abdomen. Their eyes are large, oval and “compound,” which means they are comprised of thousands of individual photoreceptors. They can see in all directions at once, and they can see all the colors that humans can, plus more.
Butterflies have two antennae located at the front of their head. They’re used for touch and for smell to help them locate food. True butterflies have antennae with club-shaped tips. Skippers’ are clubbed and hooked. Moth antennae are neither clubbed nor hooked and feature a lot of variety, including the feathery-looking ones shown below.
The mouthparts of butterflies are located between their eyes. The tongue, or “proboscis,” (pro-BOSS-sis) is shaped like and functions like a straw, which limits them to a liquid diet. Its length determines which flowers they sip from: Skippers have very long tongues, up to one-and-a-half times their wingspan, while swallowtail butterflies, for instance, have medium-length tongues and Mourning Cloak butterflies have short ones. They each sip from a different shape of flower. The tongue is coiled under when not being used. A few moth species don’t have functioning mouthparts at all and don’t feed during the adult stage of their lives.
Butterflies have six legs, which are attached to the underside of their thorax. All the legs have joints and a clawed foot, which is used for clinging. The feet contain taste sensors. In some families of butterflies, the front pair of legs is nonfunctional and kept folded.
Their abdomen is long and contains the heart, digestive system, respiratory system and sexual organs. Butterflies breathe by taking in oxygen through openings called spiracles, located on the sides of the abdomen. Click here for more detail about the internal anatomy of insects
Butterflies have two pairs of wings, which are covered by millions of overlapping scales. It’s the scales that give wings their colors. Touch the scales and they’ll easily rub off into a powdery “dust,” exposing an underlying transparent membrane. In some species, the body also has scales. The wings of true butterflies are usually brightly colored in about every imaginable hue, including metallic tones. Skippers are drabber, usually wearing dull-orange, tan, gold or brown colors. Moths are drabber still: brown, gray, black, white, or a combination. Moths’ wings often have a camouflage pattern, which helps to protect them in the daytime from predators. Coloration helps to identify butterfly species (and sometimes the difference between sexes) at a glance.
The wings are very thin and delicate and wouldn’t function without a network of stiff veins that give them structural support. Their wings can carry butterflies hundreds of miles before they wear out — they can become torn and tattered to a surprising extent and have many missing scales before a butterfly becomes unable to fly. The Painted Lady Butterfly (Vanessa cardui) reportedly can fly over 600 miles before stopping to rest.
The wingbeat of butterflies has been clocked at eight to 12 times per second, depending on the species. As for speed, the Monarch flies at about 12 miles per hour, while the fastest fliers — skippers — can fly at 37 miles per hour. As for flying altitude, look up. Way up! Some species fly at 10,000 feet.
Butterflies have senses of sight, sound, taste, smell and hearing.
They have two compound eyes, which are made up of thousands of lenses called ommatidia, as well as (usually) six pairs of simple eyes called ocelli. The acuteness of a butterfly’s vision varies during its life stage. Caterpillars can barely see. They have only simple eyes on each side of the head, which distinguish light from dark, nothing else. Adults have compound eyes, as well as simple eyes, and can see, but their vision is in the ultraviolet spectrum, very different from a human’s.
Butterflies don’t have ears, but they do have a structure called the chordotonal membrane (think of it as something like the cochlea in a human’s ear) that hears sound waves. Moths, which are nocturnal, are especially attuned to the high-frequency echolocation of bats hunting at night for insects to eat.
Caterpillars feel touch through hairs (called tactile setae) that cover the exterior of their body. The hairs connect to nerves that transmit information to their brain. Adult butterflies also have hairs covering their body, which do the same thing, including information about wind.
Caterpillars have taste cells which make a distinction between foods to eat and not to eat. Their antennae also can sense smells. Adults sense taste and smell with nerve cells located on most parts of their body — antennae, legs, feet. Their sense of smell helps them find food and mates. Some females “taste” plants with their feet to determine if they’re suitable for laying their eggs.
Butterflies can communicate with each other in several ways: visual, pheromones and physical actions (such as flying patterns and postures). In a few cases, even sound. For example, the males of Cracker butterflies (Hamadryas spp.) in South America make clicking noises with their wings during territorial disputes. And the male Asian Corn Borer Moth (Ostrinia furnacalis) emits an ultrasonic “chirp” during courtship. In 2004, a Florida University researcher discovered another S. American species, Heliconius cydno alithea, making faint clicking sounds while acting aggressively toward rivals.
Butterflies are cold-blooded, meaning they take on the temperature of their environment. They lack internal mechanisms for generating heat. Their body core functions in colder temperatures, but they need heat in order to fly. What to do? They solve this problem by basking in the sun to absorb its warming rays, their wings outstretched. If the day isn’t quite warm enough, they shiver to help generate body heat. If it’s just too cool, cloudy or rainy, they won’t fly at all. They hunker down when it’s too windy, too.
Many moth species fly in the daytime. Most, though, are nocturnal to escape predation by birds, which means they can’t use the sun to warm their wings. They get around this problem in a couple of ways. For starters, they wear a coat — in the sense that they have a thicker layering of scales than butterflies (and which gives them a furry appearance). In addition to that, they shiver to generate body heat.
For butterflies, daytime hours are spent looking for mates, mating, depositing eggs, finding food and periodically resting. Most moths live just the opposite, resting in the daytime and active at night.
You’ve no doubt noticed moths flying around streetlights and porch lights at night. It isn’t clear why they’re attracted to them. A common theory, highly simplified, is that moths navigate using celestial bodies for guidance, and lights, bright in comparison to the moon and stars, mess with their navigation system. A moth finds itself going round and round the light or even nosedives into from confusion.
Butterflies undergo “complete metamorphosis,” which means that each generation develops through four life stages: From egg to larva to pupa to adult.
Butterfly males and females find each other through wing coloration (some by using their ability to see ultraviolet scales on the wings of each other), pheromones and sound. Mating takes place on the ground or in the air. Their sex organs are located at the end of their abdomen. They couple end-to-end and may stay conjoined from minutes up to hours, depending on the species.
Most people refer to immature butterflies and moths as caterpillars, but technically they’re larva (plural: larvae; LAR-vee). The young hatch from an egg laid by their mother on the leaves of a “host” plant. Monarchs like milkweed plants for their eggs. Black Swallowtail butterflies lay their eggs on parsley and other members of the Apiaceae family of plants. The Mourning Cloak Butterfly likes willow, poplar or elm trees. Whatever the butterfly or moth chooses for her host plant, it will be one that her young will eat. In fact, larvae will starve to death rather than eat from the wrong plant.
How does she tell which plant to choose? Through taste — when she lands on a leaf, she can taste it with taste sensors in her feet. If a mated female can’t find a host plant, she’ll hold her eggs until she does, although moths are sometimes less picky than butterflies. All butterflies are herbivores, with one exception, the larvae of the Harvester Butterfly, which eat woolly aphids. Photos of a larva hatching
Larvae are slow-moving and have long, segmented bodies. They have a brain and a heart, but no eyes. Instead, they have six light receptors, called ocelli (oh-CELL-ee), on their head. They have antennae to help them feel for food. They breathe through spiracles, which are openings located along their sides. Most are equipped with legs. The number of legs varies with the species, but typically it’s three pairs of “true legs” and five pairs of “prolegs.” The true legs have joints and are located on the thorax. They’ll later become the legs of the adult butterfly or moth.
The prolegs are only temporary. Fleshy and stubby, they’re meant for grasping stems and leaves, and to help the larva move. They’re located along the abdomen and near the rear-end.
The sole mission of larvae is to eat and grow big. They usually begin by devouring their eggshell, which has vital nutrients. After that, they start eating the leaves and sometimes the flowers of the host plant. There will only be a few larvae per plant, as their mother won’t put all her eggs in one basket, as the saying goes. She’ll parcel them out, a few to each plant, nature’s way of increasing the odds that at least a few will survive if any particular plant comes under a predator’s attack. This also ensures there will be enough leaves on a plant to feed the larvae she placed there.
It’s important to consider before plucking a caterpillar off a plant. Left alone, it might become a Monarch, a jaunty little Least Skipper or one of the sphinx moths that look and fly like hummingbirds. Many larvae will not make it to the next stage of their lives, regardless. As Daniel H. Janzen, professor of biology at the University of Pennsylvania, says, “Caterpillars are food for almost every carnivore. That means birds, mammals, spiders, beetles. Everybody eats caterpillars. So it’s a sort of hamburger in the world.”
Although their life is fraught with danger, many species have defense mechanisms. Some have color patterns near their rear-end that look like eyes, all the better to “stare” and scare off timid predators. Some are colored to match their host plant. Others have spiny bristles or hairs that irritate anything that brushes against them (including a human’s skin). The jaunty-looking moth caterpillar above (Sibine stimulea) has barbed hairs that secrete a venom when touched. Some species spit acidic juices or discharge an offensive odor. There are even larvae in South America that have venom glands. Some, like the Monarch, are protected from predators because the plants they eat make them distasteful or even toxic.
Larvae eat almost constantly for usually two weeks to a month. During the eating stage, they grow astonishingly fast, faster than any other animal in the world. For example, the Tobacco Hornworm, which will become a Carolina Sphinx Moth (Manduca sexta), grows 10,000 times bigger within about 20 days. The skin of larvae can stretch to accommodate some of their growth, but it has its limitations. When the limit is reached, the larvae shed it, crawling out headfirst, wearing new skin with the ability to stretch to the next limit. They shed their skin as many as four or five times (depending on the species) and there is a name for each larval stage: instar. When the larvae first hatch they are tiny caterpillars referred to as a “first instar.” After they shed their skin for the first time they become a “second instar,” and so on.)
When a brain chemical called “juvenile hormone” is at a certain level they undergo their final molt and jettison all the contents of their digestive tract. At this point, they leave their host plant and look for a suitable, safe spot to spend the next stage of their lives. Skippers and moths usually go underground or under leaf litter. True butterflies secure themselves with a silken girdle, in an upside-down position to something like a twig, leaf or fencepost. Once they find the right spot, the larvae are set to pupate. Here’s what happens then:
With butterflies, their outer skin hardens to form a chamber within which the transformation from caterpillar to adult butterfly will occur. Their skin is now a covering called a “chrysalis” (KRIS-uh-lus). The larva inside detaches from the inner walls of the chrysalis and is now called a pupa (PEW-puh) or a chrysalis (the words are used interchangeably.) Sealed inside the chrysalis, but separate from it, the pupa may rest for a time. But soon enough it’s hard at work: Its caterpillar body mostly liquifies into what some scientists call a “nutrient soup” of pre-programmed cells that had lain dormant within the caterpillar until now. During the pupation stage, they activate and form the different parts of the body — wings, legs, eyes, etc. Weird and amazing, huh?
Moths undergo the same process of eating and molting. But when it comes time to pupate they either enclose themselves in a cocoon they spin from special silk glands or lay naked in soil or under leaf debris, where their outer skin hardens into a protective shell. Sometimes moths add bits of stuff — grass, twigs, leaves, their own hair — to the outside of their cocoon or wrap it in an entire leaf.
Some larvae of both butterflies and moths take a year to complete their life cycle from egg to adult. Many others over-winter and emerge in the spring if they began pupating in the fall. Most often, in two to four weeks, the pupal case splits open and a full-grown, sexually mature adult (called an imago (em-AH-go) by experts, greets the world.
The new imago is a pathetic sight. Its abdomen is large, full of fluid. The wings are all wet and crumpled up, looking utterly useless. In fact, they are useless, but the imago has a solution for that little problem. Literally. It begins to pump the solution stored in its abdomen out into its wings. Little-by-little, the abdomen gets smaller while the wings unfurl and take on shape, strengthened and plumped by the fluid. The butterfly turns them to the sun to grab its heat and flaps them to build muscle. These are life or death moments for the imago. If anything — say, a twig or leaf — prevents its wings from taking proper form, they’ll be useless. Unable to fly to food and water or away from predators, it’ll soon die.
Finally, when the time is right — and with its mind on food and finding a mate — it takes to the sky, as though it has done it a hundred times before. No apparent wobbling, no crashing into a tree, nor a nosedive into the birdbath.
Most species will live a few days or a few weeks as adults, with the average being around two weeks. Some species will live several months. A notable example is the Monarch, which emerges in July and August of one year, moves south to central Mexico and then migrates north again the following spring to lay eggs before dying. Monarch life cycle pictorial
Butterflies may sip nectar, sap, fermenting juices of rotting fruit, bird droppings or dung, depending on the species. Some supplement their food by sipping nutrients from mud puddles. Shallow depressions where dew or rain has collected are also frequented. A few moth species don’t eat at all as adults.
Butterflies are prey for spiders, wasps, birds and other wildlife. Most of the brightly colored butterflies are distasteful to predators. It’s thought their coloration has evolved as a successful visual warning to predators not to touch them, because it seems to work. Their nasty taste comes from the juices of certain host plants eaten by them during their caterpillar stage. The Monarch Butterfly is one example. Monarch larvae feed on milkweed, the juice of which is bitter and mildly toxic. Both larvae and adults are avoided by knowledgeable predators.
* Top photo: Giant Swallowtail Butterfly, Papilio cresphontes. (© Jack Holmes / iStock)
¹ Source for all population figures: Smithsonian Institution
² The moth is shown in a side view, in the center of the photo, hanging head down. Look for its large, round eye.