Are butterflies your favorite insects? Graceful, non-threatening, mysterious and, above all, beautiful — what’s not to like? Butterflies, along with moths, belong to the order Lepidoptera (Lep-uh-DOP-ter-uh). 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!)
The name Lepidoptera comes from the Greek libido, meaning scaly and ptera, meaning wings. Just as their name says, butterflies and moths have tiny scales covering their wings. The origin of the name “butterfly,” isn’t known, but it originated prior to the 8th century and was originally a combination of the Old English words butere, “butter,” and fleoge, “fly.” “Fly” seems obvious enough, but how did butter find its way into the name? Theories abound, but one of the most common is that certain butterflies, called sulphurs, were called “butter-colored flies” back then and eventually everything came to be called a butterfly, regardless of color. Another theory is that in days of old butterflies were thought to steal milk or butter and earned their name that way. The word “moth,” comes from the Scandinavian mott, or 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 who have thus far been described by entomologists. Fossil evidence shows that some butterfly species have been around for at least 50 million years. Lepidopterans 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 U.S. there are around 11,000 species of moths and 750 species of butterflies.
Butterflies and moths are an important food source for other animals. They’re also pollinators, as they spread pollen while moving from flower to flower. Alas, they aren’t entirely beneficial — the caterpillars of some destructive moth species continually threaten the existence of some of our favorite trees, and others do considerable annual damage to crops (not to mention our stored woolens.) Moths range in size from that of a tiny Nepticulid moth with a wingspan of 1/16-inch to the beautiful Atlas Moth (Attacus atlas) of Southeast Asia, which has a 12 inch wingspan. Butterflies range in size from the 5/8-inch wingspan of the Western Pygmy Blue (Brephidium exilis), found in the southern U.S., to the 12-inch wingspan of the Queen Alexandra’s Birdwing (Ornithoptera alexandrae), a Papua New Guinea rainforest species.
Butterflies vs moths: Lepidoptera consists of moths and a related superfamily (Papilionoidea) of “true butterflies” and “skippers.” To the unpracticed eye all three groups may seem much alike. But, you can quickly learn the difference and, at a glance, distinguish between a true butterfly, a skipper and a moth. Exceptions do exist, but they’re relatively few and you can count on the following to be reliable most of the time. Here’s how to tell the difference:
Lepidopterans have three main body parts — the head, thorax and abdomen. Their eyes are large, oval and “compound,” which means they consist of hundreds of individual photoreceptors. They can see in all directions at once, and they can see all the colors that humans can see, plus more.
Two antennae are located on the head. They’re used for touch, and they also contain organs for smell, helping them to locate food. The tips of butterfly antennae are club-shaped. The reason isn’t really known, but this may have to do with orientation. Moth antennae aren’t clubbed and have a lot of variety — they may be feathery-looking or comb-like.
Their mouth is located between the eyes. Their tongue, or “proboscis,” (pro-BOSS-sis) is shaped like and functions like a straw, which limits them to a liquid diet. It’s coiled under when not being used. 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 have medium-length tongues and Mourning Cloak butterflies have short ones. They each sip from a different shape of flower. A few moths lack functioning mouthparts and don’t feed at all as adults.
Lepidopterans have six legs and they’re attached to the underside of the thorax. In some families of butterflies, the front pair of legs is nonfunctional. All the legs are jointed and have a clawed foot. The claws are used for clinging. The feet contain taste sensors.
The abdomen is long and contains the heart, digestive system, respiratory system and sexual organs. Lepidopterans breathe by taking in oxygen through openings called spiracles, located on the sides of the abdomen. The wings are the most noticeable feature of butterflies and moths. They’re large and covered by millions of overlapping scales. The scales add color to the wings. Touch the scales and they’ll easily rub off into a powdery “dust,” exposing an underlying transparent wing. Sometimes their body also has scales. The wings of true butterflies are usually brightly colored, coming 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. Moth’s wings often have camouflage pattern, which helps to protect them in daytime from predators.
The wings are very thin and delicate, but a network of stiff veins in the wings gives them structural support. The wing beat of butterflies and moths has been clocked at eight to 12 times per second, depending upon the species. Wings carry some butterflies hundreds of miles before they wear out — they may 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 for a rest. 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 altitude, look up. Way up! Some species fly at 10,000 feet.
Lepidopterans are cold-blooded, meaning they take on the temperature of their environment. The muscles in their wings have to be warm in order to function, but they can’t generate the heat all by themselves. That’s why you’ll see butterflies early in the day sitting with wings outstretched horizontally. They’re soaking up rays of the sun, warming their muscles in preparation for flight. If the day isn’t quite warm enough, they shiver to help generate body heat. If it’s too cool, cloudy or rainy, they won’t fly at all. They hunker down when it’s too windy, too.
Most moths fly at night 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 shiver to generate body heat. But they also have a thicker layering of scales than butterflies. It’s this that gives moths a furry appearance. In a sense they wear a coat. A few moths fly in nighttime and daytime.
It isn’t clear what attracts moths to lights after dark. A common theory, highly simplified, is that moths navigate using celestial bodies for guidance, and a light or fire, which are very bright relative to stars and the moon, acts as a superstimulus. It attracts the moth, but not only that, it messes with its navigation system. It finds itslef going round and round the light or even nosedives into it out of confusion.
Lepidopterans can communicate with each other in several ways: color, pheromones and physical actions (such as flying patterns and postures). In a few cases, even sound. For example, the males of Cracker butterfly species 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 making faint clicking sounds while acting aggressive toward rivals. You can listen to this butterfly, Heliconius cydno alithea, here.
During the day, butterflies can be seen wherever there are flowers. Also look for them at mud puddles. At rest, during the day or nighttime, Lepidopterans tuck into sheltered places, called roosts, such as crevices in rock piles, woodpiles, tree bark or a small crack between a door and its frame. Often they just hang from the undersides of leaves. Moths’ coloration make them so well camouflaged it’s hard to find them during the day. Many simply cling to a tree trunk or lay on the surface of a leaf. You might find some clinging to the side of your house. Wherever they go to rest, they’ll often be camouflaged by a similar color background.
Some Lepidopterans sip nectar, while others like sap. Still others favor the fermenting juices of rotting fruit or bird droppings or dung. Some butterflies and moths are also seen sipping at mud puddles, it’s thought they’re taking in nutrients. Shallow depressions where dew or rain has collected are also frequented. There are a few moths who don’t eat at all as adults.
Life cycle Monarch life cycle pictorial
Lepidopterans undergo complete metamorphosis: This means that each generation develops through four stages: From egg to larva to pupa to adult.
Lepidopteran parents find each other through wing coloration (some by using an 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 the 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). 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 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 (LAR-vee) 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. Almost all Lepidopterans are herbivores, but one exception is the larvae of the Harvester butterfly; they eat woolly aphids.
Caterpillars 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 pair of “true legs” and five pair 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 attached along the abdomen and near the rear-end. The sole mission of larvae is to eat and grow big. They usually begin by eating their eggshell and after that, they begin 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.
It’s important to try to identify a caterpillar before you pluck him off a plant. Left alone, it might have become a Monarch, a jaunty little Least Skipper or one of the sphinx moths who look and fly like Hummingbirds. Many larvae will not make it to the next stage of their lives. 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 other larvae spit acidic juices or discharge an offensive odor. There are even larvae in South America who have venom glands. Others, like the Monarch, are left alone because the plants they eat make them distasteful or even toxic.
The 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. The Tobacco Hornworm, for instance, which later becomes a sphinx moth, grows 10,000 times bigger within about 20 days. The skin of larvae will stretch to accommodate some of their growth, but it has its limit. 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, upside-down and with a silken girdle, to something like a twig, leaf or fencepost. Once they find the right spot, the larvae are set to pupate. Here’s what happens:
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 “chrysalis””(KRIS-uh-lus). The larva inside becomes detached 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 he’s hard at work. His caterpillar body mostly liquifies into what some scientists call a “nutrient soup” of pre-programmed cells that had lain dormant within the caterpillar. During pupation 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. Mostly, though, in just two to four weeks, the pupal case splits open and a full-grown, sexually mature adult butterfly or moth, called an imago (em-AH-go), greets the world.
The imago’s abdomen is very large, because it’s 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. It begins to pump the liquid 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. It 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, like it’s done it a hundred times before. No apparent wobbling, no crashing into tree trunks. Not even a nosedive into the birdbath.
As adults, most species will live a few days or a few weeks, with the average being around two weeks. Some species, though, will live several months as an adult. A notable example are the Monarchs in North America that emerge in July and August of one year, move south to central Mexico and then migrate north again the following spring to lay eggs before dying.
Lepidoptera are prey for spiders, wasps and birds. Most brightly colored butterflies are distasteful to predators. It’s thought their coloration has evolved as a successful visual warning to predators not to touch, because it seems to work for them. 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. As adults, Monarchs are avoided by knowledgeable predators.
*Top photo: Giant Swallowtail Butterfly, Papilio cresphontes. (© Jack Holmes / iStock)