When you think of moths, what comes to mind? Maybe you remember the annoying ones beating against the porch light and flying in the open door, the clothes moth that chews hole in your silk or wool garments, or the big green caterpillar called the tobacco hornworm that devours your garden tomatoes. Do you think of the dreaded spongy moth (previously known as the Gypsy moth) that wreaks havoc on trees? While a nuisance or even destructive, these bothersome species are only a few of the moths found worldwide. Moths come in a myriad of shapes and sizes and most do not deserve this bad reputation. Moths and butterflies belong to the order Lepidoptera, but moths out-number their better-known cousins. According to the Smithsonian, there are about 160,000 species of moths worldwide and 11,000 of these species reside in North America. In contrast, there are 17,500 species of butterflies in the world. Moths are also older than butterflies. Moths co-evolved with angiosperms, or flowering plants, and the oldest moths arrived some 300 million years ago. Moths developed their long, tube-like proboscis and started pollinating flowering plants about 241 million years ago. They pre-date bees which appeared about 113-132 million years ago. Butterflies evolved from moths about 100 million years ago and so are the youngest of the group. Moths have been laboring in relative obscurity for millions of years while bees and the more famous Lepidoptera, butterflies, have been widely studied. Recent studies are learning more about moths and their contributions to pollination and the ecosystem. It is time to pull back the veil and learn more about these fascinating creatures.
Butterfly or Moth
Many moths and butterflies are similar in appearance but there are striking differences. While there are no hard and fast rules, here are some key differentiators:
- Butterflies are usually diurnal (active during the day).
- Moths are usually nocturnal (active at night) or crepuscular (active at dawn and dusk).
- Butterflies often have brightly colored wings.
- Moth wings tend to be earth colored with muted patterns.
- Butterflies rest with their wings folded upright and together.
- Moths tend to rest with their wings flat or over their bodies, covering their abdomens.
- Butterflies have long, slender antennae, often with a clubbed ends.
- Moths usually have short antenna that may be feathery.
- Butterfly bodies and legs are long and thin.
- Moth bodies and legs are short and plump.
- Butterflies pupate in a chrysalis. Butterfly larvae (caterpillars) shed their skin several times as they grows. In their final molt, they form a protective skin called a chrysalis from which adult butterflies emerge.
- Moths pupate in a cocoon. Moth caterpillars do not make a protective shell from their own bodies, but spin silken threads around themselves, forming a hard casing called a cocoon. Sometimes they spin dirt or leaves into the cocoon to help camouflage it. Adult moths emerge from the cocoons.
Moths as Pollinators
All day long, the garden is full of life as butterflies, bees, wasps and beetles go about their business pollinating plants. When the sun goes down these diurnal creatures turn in, and nocturnal pollinators, moths, take over. With twice as many moths as there are bees, and six times as many pollinating moths as there are pollinating butterfly species, their contribution to the reproduction of plants cannot be ignored. Like butterflies, moths get their nutrients by sipping nectar from flowers. In doing so, they pick up pollen on their hairy bodies and spread it from flower to flower, allowing the plant to reproduce. Moths visit a variety of flowers, including some that bees, the powerhouse pollinators, do not visit. Moths also can fly longer distances than bees, enabling them to visit a diversity of floral groups across the landscape, increasing biodiversity.
While we have learned more about moth contributions to pollination, the relationship between moths and plants is complex and still being studied. Moths evolved with plants and have adapted to one another. The body size and mouth shape of insects relate to the shape and size of flowers, determining which are the best pollinators. Moths and butterflies with their long proboscises can drink nectar deep in tubular flowers. Color plays a role as moths are attracted to white or light-colored flowers which are easy to see at night. Some flowers are nyctinastic and close at sunset but others stay open or open in the evening making nectar and pollen available for the night shift. Some species of plants and moths depend on one another to complete their life cycles. In the 19th century, Charles Darwin noticed that some orchids in Madagascar had nectar at the end of 12-inch long tubular flowers. He hypothesized that these orchids could only be pollinated by moths with proboscis long enough to reach deep into the flower. His ideas were controversial at the time and were only proven when a moth with a 12-inch proboscis was discovered many years later. The yucca plant (Hesperoyucca whipple) is only pollinated by the yucca moth (Tegeticula maculata). In this unusual relationship, the female moth gathers pollen grains from the flower at night and carries them in her mouth to another yucca flower. She pollinates the plant by depositing her egg and pushing in the pollen. When the larva hatches, it feeds on the seeds that have developed.
In addition to their value to wild and landscape plants, moths should get more credit for their contribution to agriculture. Studies at the University of Arkansas found moths congregating on blueberries, blackberries and peaches. When studying apples, they found that moths pollinate as many blossoms at night as bees pollinate during the day. This is a complex relationship, however as there is a paradox. The larvae of two of the common moths found at night in apple orchards are the cutworms and army worms which feed on vegetation and can harm apple trees. More study is needed to see if and how this paradox can be managed and which other crops benefit from night pollination.
Some Common Moths
Moths cannot be pigeonholed as they have a have a variety of physical characteristics and habits. Some are large, others small. Some are brightly colored, others drab. Some are diurnal, others are nocturnal or fly at dawn and dusk. Many are important pollinators, others do not feed as adults. All larvae (caterpillars) feed voraciously until they pupate. Most feed on a variety of plants and do little harm. Others are known as agricultural pests. All moths and their caterpillars are part of the food web and integral to the ecosystem. Moth species are prolific so it is and impossible to list more than a few here. The following are a some moths commonly seen in the Mid-Atlantic.
Sphinx and Hawk Moths (Family Sphingidae)
Sphinx and Hawk moths are among the most visible and interesting moths. There are about one hundred species of moths from the Sphingidae family in North America. Sphinx moths are large insects with stout abdomens and large front wings and don’t look like our idea of Lepidoptera. With fast moving, buzzing wings, they are often mistaken for hummingbirds. Some are nocturnal but many fly during the day. Excellent flyers, some species fly up to 30 miles per hour and can fly sideways. They rapidly beat their wings to hover above flowers, extending their long proboscis deep into blossoms without landing. The snowberry clearwing (Hemeris diffinis) and the hummingbird clearwing (Hemaris thsysbe) are both diurnal and are often encountered in the home garden. Snowberry clearwings have yellow and black bodies and clear wings. Their resemblance to bumble bees help protect them from predators. Hummingbird clearwings have a similar shape and size as snowberries, but their red and olive green coloring emphasize their resemblance to hummingbirds. Snowberry and hummingbird clearwings drink nectar from a variety of flowers and their caterpillars feed on native bee balm, phlox, milkweed, thistle, honeysuckle, dogbane, hawthorne, viburnum, cherry and plum trees. They are not a significant pest in orchards since so many other host plants are available.
Clearwing Moths (Family Sesiidae)
Clearwings have smooth rather than hairy bodies, transparent wings, and yellow and black patterns on their bodies. They resemble wasps, making them unattractive to predators. Like sphinx and hawk moths, clearwings feed on nectar during the day. Their larvae burrow into the stems of host plants, sometimes causing damage. The eupatorium borer (Carmenta bassiformis) often feeds within the stems of ironweed and Joe Pye weed.
Silkworm and Royal Moths (Family Saturniidae)
The members of this family are often colorful and some can be as large as a human hand. They do not have mouth parts or digestive systems so do not feed as adults or visit flowers. The live off the energy reserves they stored as caterpillars and devote their short lives to seeking mates and reproducing. They are not pollinators, but as both adults and caterpillars, they are food for predators and part of the food web. They fly at night so are not often seen. These moth caterpillars feed on hardwoods such as wild cherries, oaks, hickories and walnuts. Many of these moths are beautiful. Common moths in the family Saturniidae are luna (Actias luna), Io (Automeris io), rosy maple (Dryocampa rubicunda) and polyphemus (Antheraea polyphemus).
Tiger Moths (Family Arctiidae)
Some members of this family are brightly colored and rely on chemical defenses rather than camouflage for protection. They visit flowers in gardens and along roadsides for nectar. Arge moths (Gramma arge) are large and can be white, orange, or pink with black strips and dots. The harnessed tiger (Apantesis phaletera), giant leopard (Hypercompe scribonia), and milkweed tussock (Euchaetes egle) are also members of this family. Fuzzy “wooly bear” caterpillars can be seen in late summer and tussock moth caterpillars sporting fuzzy spines are larvae of tiger moths. Tiger moth caterpillars feed on a range of native and other plants such as apple, cherry, dandelion, oak, sunflower, violets and walnut.
Owlet Moths (Family Noctuidae)
Owlet moths are a large family and a very common group. Unfortunately, some in the family have a bad reputation: cutworms and army worms are agricultural pests. Adult owlets, however, are great pollinators. They visit goldenrods, asters, rudbeckia, gaillardia, witch-hazel and columbine. Some also feed on plant sap and rotting fruit. Most owlets are small, stout, and drab, camouflaged with lines and spots to resemble tree bark. Some fool predators with coloring that resembles bird droppings. Others are colorful, their bright markings indicating their toxicity to predators. They are nocturnal and attracted to lights.
Threats to Moths
Like butterflies, bees and other pollinating insects, the number of moths has decreased alarmingly. Habitat loss, pesticides and the proliferation of invasive species overtaking native plants have all contributed to decline of moth populations. Air and light pollution add to the threats to nocturnal pollinators.
Researchers at the University of Washington found that hawk moths and sphinx moths use their antennae to detect nectar in primroses as far away as a mile. However, NO3 , a common pollutant formed from car emissions and other industrial sources, builds up in the air at night and degrades the scent of flowers. Experiments showed that hawk moths and white-lined sphinx moths had trouble flying in the presence of NO3 at the levels found at night in urban areas; researchers determined that moth visitation to flowers dropped by 70% in the presence of NO3. While this study only included two species, it indicates that air pollution affects the plant community and its pollinators in a big way.
Researchers at Florida International University have studied the effects of artificial lights on moth behavior. It is believed nocturnal moths have great low light vision and that too much light causes problems for them. Moonlight and starlight actually help moths maneuver at night and helps them travel long distances. In the presence of bright, artificial light, however, moths become disoriented. For reasons not understood, they are attracted to bright lights, as in the saying, “like a moth to the flame.” The tendency to fly toward artificial lights is fatal. When moths get near bright lights, they no longer act like night pollinators. They stay stunned near the light source and don’t look for mates. The stunned moths become prey to predators and, by not pollinating, reduce seed production. The amount and brightness of lights in urban and residential areas has increased and is contributing to the decline of moth populations.
Gardening for Moths
Sometime around 2600 BC, a silkworm cocoon dropped into the teacup of the Chinese Empress Leizu. She unwound the threads, discovered silk and soon mulberry trees were cultivated for silk production. Today, more than 700,000 tons of silk are produced annually by domesticated Asian silkworms. Home gardeners can create a haven, if less grandiose, to attract moths. To create a moth-friendly habitat, select the same native trees, shrubs and perennials that attract bees and butterflies. Joe Pye Weed (Eupatorium maculatus), goldenrods (Soildago) and rose mallow (Hibiscus moscheutos) are useful varieties for moth pollinators. In addition, here are some additional plant types important to moths.
- Pale and light-colored flowers that reflect moonlight and are easier for nocturnal moths to find in the dark
- Flowers that stay open at night such evening primrose (Oenothera biennis)
- Blossoms with long, tubular blossoms such as foxglove beardtongue (Penstemon digitalis) and scarlet beebalm (Monarda didyma) to accommodate the long tongues of moths
Nectar-feeding moths also feed on tree sap and rotting fruit. Gardeners should also protect moth caterpillars by providing host plants for them to eat. This is especially important for moths that do not feed as adults. In the Mid-Atlantic and Southeast, some moth-attracting plants for both adults and caterpillars are oak (Querucs species), willow (Salix), chokecherry (Prunus virginiana), spicebush (Lindera benzoin), and buttonbush (Cephalanthus occidentalis).
See Piedmont Master Gardeners, Creating Habitat for Lepidoptera in The Garden Shed for more information.
Photo by Deborah Harriman
Summary
- Moths outnumber their Lepidopteran cousins, butterflies, almost ten to one.
- Most moths, both diurnal and nocturnal, are important pollinators.
- Moths undergo complete metamorphosis: egg, larva, pupa and adult.
- Some moth caterpillars are agricultural pests, but most feed harmlessly on wild plants.
- Moths are important to the ecosystem. In their adult and larval stages, they are food for birds and other animals, contributing to the food web.
- Some adult moths do not feed, live only a short while, and exist only to mate and reproduce.
- Moths are diverse in size, shape and color. Some are muted with colors that camouflage them from predators. Others are brightly colored and deter enemies with chemical properties. Some are tiny, others as large as a human hand.
- Plant flowers for nectar and host plants for caterpillars.
- Avoid pesticides.
- Turn off outside lights.
Sources
Air Pollution Hurts Pollinators, Xerces Society
Gardening for Butterflies, The Xerces Society, Timber Press, 2016
Into the Night: Shedding Light on Nocturnal Pollinators, University of Arkansas Division of Agriculture
Moths are the Unsung Heroes of Pollination, Smithsonian Magazine, July 28, 2022.
Moths, Butterflies and Pollinations, University of Maryland, Maryland Agronomy News
Moths – The Forgotten Pollinators, Penn State Extension, Monroe County News
Make Your Garden a Haven for Moths, NC State Extension
Noctuid Moths, Missouri Department of Conservation
Owlet Moths (Mesogona olivata), U.S. Forest Service, U.S. Department of Agriculture
These Moths are so Gorgeous, They “Put Butterflies to Shame”, Smithsonian Magazine, July 19, 2021.
New Research from Riffell Lab On Air Pollution Affecting Nighttime Pollinator Activity University of Washington
Feature Photograph:
Io Moth, Photo by Sturgis MdKeever, Georgia Southern University, Bugwood.org
