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Flutterly Fascinating

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Published on: Jun. 2, 2009

Last revision: Dec. 14, 2010

A moth fluttering through the air on a summer night suddenly hears the calls of a bat in pursuit of a meal. The moth vibrates tiny membranes on its thorax in response. These are meant to momentarily confuse the bat’s interpretation of the echoes its calls return, allowing the moth to escape. When the bat continues to close in, the moth stops flying, closes its wings and plummets to the earth in a final attempt to elude the predator.

Beautiful and interesting animals are living out their lives in your backyard. Christened with exotic names such as green marvel, cynical quaker and promiscuous angle, Missouri’s moths are just outside your home almost every summer night, mating, laying eggs, feeding and escaping from predators.

Although almost everyone likes butterflies, most people are lukewarm when it comes to moths. That’s because people generally tend to think of moths as dull and butterflies as colorful. However some moths, such as painted lichen moth, grapevine epimenis, and banded tiger moth, outshine many butterflies.

Sometimes it’s hard to tell whether you are looking at a moth or a butterfly. Some of the distinctions between the two groups are visible only under a microscope. It’s true, however, that butterflies are generally more active during the day, while many moths are nocturnal. Butterflies also hold their wings either out to the side or folded together over their bodies, while most moth wings are angled like an A-frame roof.

In North America, the most reliable way to distinguish moths from butterflies is to look at the antennae. Butterflies have thin antennae with clubs at the tips, while moth antennae are either threadlike, narrowed at the tip or feathered.

Feathered antennae are generally larger on males and play an important function in reproduction. Those feathery antennae are sensitive to the chemicals in pheromones released by females to attract potential mates.

Crickets use sounds to find mates in the dark; moths accomplish the same thing with scents. Females release pheromones from abdominal glands at a specific time. This “calling time” can help prevent moths with similar pheromone chemicals from finding the wrong mate.

Females select nights with a light breeze to disperse the pheromones, but not so windy that the pheromone plume is distorted. Male moths that have been marked and released have been caught in traps baited with female pheromones more than 20 miles away.

Staying Alive

Staying alive long enough to reproduce is critical to an animal’s success. Many moths have evolved unique markings and coloration to help them blend into the background, look like an object nothing wants to eat or warn a predator that it is inedible.

The orange wing moth is often seen flying through the woods in early spring. While only the hind wings are orange, it looks bright orange in flight so a bird in pursuit forms a search image of an orange moth. When the moth lands, the bird’s target disappears as the brown forewings conceal the orange.

Bird-dropping moths rest on the top side of leaves, their scales a mixture of white, gray, and brown, looking just as their name suggests, which is a great way to avoid being eaten. Other moths have brown, gray, and black scales to help them blend into tree bark, where they rest virtually invisible throughout the day.

Some tiger moth caterpillars absorb chemicals from plants that make animals that eat them sick. Those chemicals are retained in the bodies of the adult moths. Some moths also have tough bodies that can survive the first bite; red, black, white and yellow scales that warn predators not to eat them; and the ability to make high-pitched noises in flight to warn bats.

The black and brown woolly bear seen crawling over the ground in the fall is a tiger moth. It’s edible, but it makes the warning sounds made by the inedible tiger moths. It’s a mimic, gaining protection by imitating another species.

Luring Moths

To attract more moths to your yard for easy observation, you can plant flowers that produce nectar, you can smear moth bait on tree trunks, or you can leave a light on. Not all species are attracted by all three methods, but by trying all of them, you should see a wide variety of moths.

Most adult moths feed on nectar, fruit or sap, just like butterflies. A variety of day-flying moths visit the same flowers as butterflies. Watch for bright orange, white, and black ailanthus webworm moths at dogbane; snowberry clearwing moths at bee balm. Spotted Beet webworm moths, along with a variety of other moths and butterflies, are attracted to sedum and catmint.

Most moths are active at night. Flowers that rely on moth pollination are often white, heavily scented or both. Their fragrance is released once the sun sets and is highly attractive to moths. In one study, sphinx moths released 300 yards from flowers bolted straight for the flower bed, presumably following the scent. Plant four o’clocks, dame’s rocket, and night-blooming nicotanias to attract moths to your yard.

Sphinx moths learn where their preferred flowers are and follow a set route each day, stopping to sip nectar along the way. Several years ago, a single yellow evening primrose in my yard opened each day at dusk. Like clockwork, the petals unfurled at the same time each night. For about one week, just moments after the flower opened, a sphinx moth hovered in front of the flower sipping nectar.

In addition to planting flowers, try luring moths with sweet, fermented bait. Instead of throwing out overripe bananas, mash them and stir in a few spoonfuls of brown sugar and about half a can of beer. The exact amount can vary, and you can use other overly ripe, mashed fruits. Let the mixture ferment at room temperature for a day or two for best results and store any leftovers in the refrigerator for about a week. The bait should be a thick mixture that you can spread onto about one square foot of a tree trunk with a new paintbrush. Brushing it onto several trees in the same area will increase the chances of insects finding your bait. A wide variety of moths, including zales and underwings, are attracted to bait.

If you check your bait during the day, you might find butterflies, such as red admirals, goatweed leafwings and question marks. Use caution with bait if you live in an area of the state with black bears. Wasps may be at the bait during daylight hours but are usually docile because they are away from their nests.

Moths and Lights

Everyone knows that moths can be found at lights. Current thinking is that moths aren’t really attracted to lights, but are trapped by them. Bright lights at night cause a sensory overload. Scientists think moths see dark areas either adjacent to or in the center of the light source. Moths try to fly towards that dark area, but as they move, their perspective changes, and they continually change directions, remaining in the vicinity of the light.

An older explanation for why moths are attracted to lights is that moths use the moon for navigation and confuse artificial lights with the light from the moon. If a moth is flying at a specific angle in relation to the moon and then transfers that angle to an artificial light, it will continually alter its flight path as it passes the light, eventually spiraling in close to the bulb. In response to bright light — or daylight — moths land.

Whatever the attraction, lights are a good way to get a look at moths not enticed by flowers or bait. Silk moths, such as the luna moth, do not feed as adults. They live only about a week as adults, subsisting on walnut or hickory leaves eaten as caterpillars.

You can attract many moths with your porch light, but if you are serious about finding a wide variety of moths, use either a mercury vapor bulb or a black light. Those bulbs produce different wavelengths of light which attract different species. Try not to leave your lights on every night; moths and other insects will be drawn to the light instead of engaging in normal behaviors.

Many people think of moths (and most other insects) as pests, believing all moths eat clothes and crops. In reality, only about 2 percent of all insects worldwide cause problems, such as feeding on crops or transmitting diseases. The rest are critical components of ecosystems. Learning more about moths and their life histories will help you understand basic biological concepts including species interactions, ecological adaptations, and the importance of conserving biodiversity.

Take a few steps out your door and check out the moths in your yard. A fascinating world awaits you.

A Moth Photo Collection

You can use a compact digital camera to create a virtual moth collection, avoiding the upkeep of a traditional collection. Keep records of the moths seen in your yard or neighborhood park. More than a hundred species can easily be found in most yards in a year.

Moth Learning Library

The Department of Conservation’s Butterflies and Moths of Missouri by J. Richard and Joan E. Heitzman is a good starting point for learning more about Missouri’s moths. It includes 833 color photos and descriptions of 324 species. Range, habits, size and status of each are included in the 385 pages. Butterflies and Moths of Missouri is available for $18 plus shipping and handling, and sales tax (where applicable) by calling toll free (877) 521-8632 or visiting our online Nature Shop or at Conservation Nature Centers statewide.

A Field Guide to Moths of Eastern North America by Charles V. Covell, Jr., covers many more species of moths than the state guide.

Discovering Moths: Nighttime Jewels in Your Own Backyard is John Himmelman’s entertaining story of his adventures searching for moths. He provides information on their biology, including time of year when certain moths are most likely to be seen, along with insight into attitudes toward moths.

One of the best online resources for not only moths, but all insects, is BugGuide (see link below). You can search through photographs or submit a photo and ask for identification help. Frequently, you’ll have your answer within the day.

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