Image of datana moth

Night Beauties: 4 Ways to Help Moths in the Garden

Image of brown hooded owlet moth caterpillar on heath aster

For every documented butterfly species in North America, about 15 times more moth species inhabit our gardens and natural areas. Yet they’re far less known to us than their charismatic day-flying counterparts, perhaps because most moths are active long after we’ve hit the sack.

Though they often escape the notice of humans, moths are essential to many other species, including plants that depend on them for pollination and animals who eat them for nourishment.  As caterpillars, they’re a mainstay of the diets of baby birds. As adults, they feed everyone from bats to bears; in fact, researchers have found that grizzly bears at Yellowstone National Park eat up to 40,000 miller moths (adults of the army cutworm caterpillar) each day.

Our judgment of an animal’s worth should not be measured only by their potential to be prey for other species, though. Like all our wild neighbors, moths have intrinsic value of their own and deserve just as much respect, appreciation, and freedom from harm as butterflies do. Here are a few ways you can help these unassuming creatures in your garden and neighborhood.

1. Put down the spray bottle

Image of grape leaf folder moth
As caterpillars, larvae of the beautiful grape leaf folder moths do exactly what their name implies, spinning silk to tie leaves around themselves and nibble without being seen.

Much of the easily accessible information about moth caterpillars is confined to academic and agricultural sites that refer to these animals as “pests” because they dare to chew holes in leaves. All sorts of chemical potions are recommended for destroying the supposed enemy. But everyone has to eat, and I rather appreciate nature’s vegetarians. The grape leaf folder moth pictured above has likely taken up residence in our yard because this year we have an abundance of wild grapevines, their larvae’s favorite food.

image of tiger milkweed moths
Tiger milkweed moths like to hang out in packs on butterflyweed and other milkweed species.

Tiger milkweed moths also set up shop at this time of year, though the caterpillars are more gregarious than the adults. Sometimes gardeners are upset by the voracious appetites of these fuzzy creatures, worried there’ll be no food left for the monarch butterfly larvae, who also depend on milkweed. But these two winged species tend to have different palates. Tiger milkweed caterpillars join the buffet when plants have aged a bit, while monarch caterpillars prefer young, fresh milkweed leaves.

2. Plant native species they recognize

Image of brown-hooded owlet caterpillar
A brown-hooded owlet caterpillar munches on a heath aster, a white-flowering native that volunteered in my garden a few years ago and has since spread.

Plant names are sometimes embedded in the common names of some moth species or their caterpillars. There’s a good reason for that; like butterfly larvae, moths in the teenage phase often nibble only on vegetation they coevolved with. Common oak moth larvae eat oaks, locust underwing moth larvae munch on locust trees, and caterpillars of the hickory horned devil—whose more appealing adult name is “royal walnut moth”—dine on hickories and walnuts.

Image of bicolored pyrausta
A bicolored pyrausta (we think) visited a cutleaf coneflower by my patio last weekend.

But many moth names seem to bear no relationship to the plants the animals depend on: Brown-hooded owlet moths eat asters and goldenrod, and Pandora sphinx moths eats Virginia creeper and grapes. The larval host plants of some species aren’t even yet known; after moth expert Dr. David Adamski helped me tentatively identify a small orange moth in my garden as a bicolored pylautus, I searched references for her preferred foods only to learn that scientists haven’t yet figured it out. The lesson for me? Plant even more native plant species! You never know who might need them.

Yuccas and yucca moths provide an exquisite example of the fascinating mutualistic relationship between animals and plants. The yuccas receive the benefit of pollination from the moths, and the moths lay their eggs in the flowers, where larvae hatch and eat the abundant seeds. Wondering why I’d never witnessed moths among the many yuccas scattered around our gardens, I finally ventured outside around 10 p.m. earlier this summer and found more action than I’d ever imagined. It really gets going at the 27-second mark in this video taken by my husband:

3. Let there be dark

Image of giant silk moth
A polyphemus moth in our neighborhood appeared to be on her last legs – or wings – when my husband scooped her up from the road and placed her in the grass.
image of polyphemus moth caterpillar
A polyphemus moth caterpillar, brought to a presentation at City Wildlife in Washington, D.C., rests on an oak leaf.

Recently while researching a magazine column about gardening for bats, I was alarmed to find that some experts support leaving lights on to unnaturally attract moths for an easy food supply. Light pollution negatively affects giant silk moths and has led to the decline of other large species, including the royal walnut moth. “The preponderance of lights where there used to be forest is taking a heavy toll on these wonderful animals throughout their range,” writes entomologist Doug Tallamy in Bringing Nature Home. “Royal walnut moths have already disappeared entirely from New England.”

image of hickory horned devil
We felt lucky that our garden was home last year to the royal walnut moth’s caterpillar, called the hickory horned devil, a species threatened by light pollution.

As adults, these moths live for only a few days and don’t eat; lacking mouth parts, they survive only on the energy they stored up as caterpillars. Their primary function is to breed, but if they spend their nights circling the security lights in someone’s front yard, they run out of energy to mate and lay eggs.

Though bats are declining in number and face many threats themselves, it doesn’t make sense to harm one type of animal to help another–not to mention the fact that hurting species that serve as bats’ main food supply will only exacerbate the plights of bats, too. To save these moths from further decline, turn off outdoor lights at dusk, or install motion-detecting lights that don’t burn throughout the night.

4. Don’t equate tidiness with godliness.

Image of hummingbird moth
When not flying among our flowers, hummingbird moths rely on the garden’s leafy layer as caterpillars, taking shelter there in the winter.

We’re used to seeing hummingbird moths enjoying the wildflowers in our gardens, but they’d never reach this beautiful adult phase if we raked out too many leaves from the understory. These creatures overwinter as pupae in the natural ground layers, emerging in spring and summer as adults.

In fact, many species of butterflies and moths take shelter there, along with toads, queen bees, and countless other creatures who need to wait out the winter storms in decaying plant material we too often blow and rake away. This fall, leave the leaves and other natural material in place, and watch how many more species begin to take up permanent residence in your humane garden.

Photos by Nancy Lawson. Video by Will Heinz. Featured image: A Datana moth rests on a spicebush leaf.




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