Gardening for Wildness: Garden Moths

Far less conspicuous than butterflies are the thousands of North American moth species, their muted colors and nocturnal lives keeping most of them out of sight and thus out of mind.  I am was reminded of their existence, however, when I forgot to turn off the porch light one warm spring night, waking at daybreak to a porch wall covered with moths of all sizes and patterns.  This was how I discovered the rosy maple moth (Dryocampa rubicunda), one of the most colorful moths with creamy white and pink wings folded over a yellow body.  Since our garden is surrounded by numerous red maples, a key larval host plant for this species, I have to assume that they have always been around, yet unnoticed but for that one day.  (I do not recommend this as an approach to moth watching as it leaves the moths exposed through the day to predators.)

Two primrose moths pollinating primrose blossoms.

Two primrose moths pollinating primrose blossoms.

Like butterflies, most moths are incidental pollinators, the exceptions being for a few specialized plants that depend on moths for their survival.  For example, the evening primrose (Oenothera biennis), a common wildflower along the lane that leads to Marjorie’s Garden, depends upon the primrose moth (Schinia florida) for pollination.  In exchange for this service, the female moth lays her eggs within the flowers so that her caterpillars can feed on the plant’s developing seed pods.  This mutualism benefits both species, enhancing the genetic diversity of primrose populations through cross pollination.  The primrose moth’s bright pink forewings make it one of the most colorful of North American moths.

A bumble bee moth resting on a tobacco leaf.

A bumble bee moth resting on a tobacco leaf.

Not all moths are nocturnal creatures.  On late summer afternoons we watch bumble bee moths (Hemaris spp.) hovering like hummingbirds in front of the long white tubular flowers of annual tobacco (Nicotiana alata), sipping nectar with their long proboscises.  Mimics of bumble bees, a trait which allows them to avoid many would-be predators, these moths are extremely fast fliers, reaching velocities of more than 30 miles per hour.  Lacking the scales common to most butterflies and moths, their wings are nearly clear, giving them the alternative common name of “clearwings”.

In addition to flowering tobacco, bumble bee moth adults nectar on thistles, lilacs, orange hawkweed, snowberry, dwarf bush honeysuckle, and lantana.  They lay their eggs on snowberry (Symphoricarpos albus), dwarf bush honeysuckle (Diervilla lonicera), and dogbane (Apocynum spp.), the first two species being among the best of native shrubs for the ornamental garden.  The eggs hatch after about a week and the caterpillars, often called hornworms, feed on the host plants for about a month, then pupate on the ground within a sturdy cocoon covered with leaf litter.  After several weeks, the adults emerge and lay another generation of eggs.  Second generation larvae undergo metamorphosis during the winter.

The Virginia ctenucha, a most colorful moth.

The Virginia ctenucha, a most colorful moth.

With its metallic blue body, orange head, and dark grey-brown wings, the Virginia ctenucha (Ctenucha virginica, the first “c” silent) is one of the most colorful diurnal moth species visiting our garden each summer.  It is known as a food plant specialist, the larvae feeding solely on grasses, sedges, and irises.  Adults sip the nectar of a variety of plants, including goldenrod.  Its common name belies its distribution as it is typically a northern species with Virginia as it southernmost range.

Thought to be native to south Florida and the American tropics south to Costa Rica,

The ailanthus webworm caterpillar.

The ailanthus webworm caterpillar.

the ailanthus webworm (Atteva aurea) cannot survive cold winters and yet there it was, nectaring on goldenrod in our summer garden, a slender moth with bright orange wings marked with white spots bordered in black, forming a pattern of tiny stained-glass windows.  A little research revealed that moths of this species migrate north each year, making it as far as eastern Canada, relying on the invasive tree species called tree-of-heaven, Ailanthus altissima, as the primary larval host.

The paddled dagger moth caterpillar munching on a blueberry leaf.

The paddled dagger moth caterpillar munching on a blueberry leaf.

Many other moth species make their presence know in Marjorie’s Garden by the feeding of their  caterpillars on garden plants.  Some of these moth larvae are ubiquitous in the summer garden while others are rare, perhaps seen only once.  For example, one late mid-August afternoon Marjorie came in from the garden with a bowl of berries and announced that there was an unusual caterpillar on one of the highbush blueberry shrubs.  I rushed to the garden with camera in hand and took several shots of the creature as it munched a blueberry leaf.  Typically when you find one caterpillar there are others of the same species nearby, but a thorough search of all the garden’s blueberry shrubs did not turn up another like it.  The back of its coal black body was lined with orange and white football-shaped pads, each sporting a slender black filament with a paddle-shaped tip.  That evening I keyed it out as a paddled dagger moth larva, Acronicta funeralis, and learned that it deters potential predators by rotating those paddles.

Whenever I find a new species in Marjorie’s Garden, I try to understand how it fits into the garden food web.  In the case of the dagger moth caterpillar, I learned that highbush blueberry was but one of several larval host plants for A. funeralis.  I might also find it feeding on alder, apple, birch, dogwood, hazel, maple, oak, or willow, all of which occur in or around Marjorie’s Garden.  I also learned that our sighting of this creature was a rare event, that some lepidopterists go their entire life without seeing the elusive dagger moth caterpillar.

The tussock moth group is well represented in our summer garden, the hairy caterpillars often found crawling across porch walls and steps.  I recall one summer when the numbers of one tussock moth species reached such proportions that panicked gardeners called wanting to know what they could do about all those hairy caterpillars.  My answer was always the same: “be careful where you step.”

A hickory tussock moth.

A hickory tussock moth.

Tussock moth caterpillars are typically hirsute creatures, covered with alternating bristles and haired projections.  Many species have short irritating bristles that can sting on contact.  Certainly the black and white hickory tussock moth (Lophocampa caryae) is one of these and care should be taken when moving it off the porch.  The larval host plants for this species include ashes, elms, hickories, maples, oaks, and other trees.

My favorite among the tussock moths is the milkweed tussock moth, Euchaetes egle.  I say this with some exasperation, as

Two milkweed tussock moths feeding on milkweed leaves.

Two milkweed tussock moths feeding on milkweed leaves.

I watched a horde of these caterpillars completely consume a first year planting of swamp milkweed intended for the future benefit of monarch butterfly larvae.  Still, the milkweed tussock moths were a delight to watch as they grew from the tiny slightly hairy first instar larvae to creatures that looked like “Cousin It” of Addams Family fame, all within less than a month’s time.  They skeletonized an entire plant’s leaves in a matter of hours, eventually reducing a stand of milkweeds to slender leafless stalks.

Winner of the award for “Best Dressed Tussock Moth Caterpillar” is the white-

A white-marked tussock moth.

A white-marked tussock moth.

marked tussock moth, Orgyia leucostigma.  With a bright red head, yellow- and white-striped body with a black stripe down the middle of the back, bright red defensive glands on its rear end, four white toothbrush-like tufts along its back, and a dark tuft of hair on its hind end, there is no way this caterpillar is going to hide among the foliage.  Clearly its colorful markings are a warning: touch me and pay a steep price.  Indeed, brushing against the hairs causes allergic reactions in many humans, yet some birds are able to eat these caterpillars.  White-marked tussock moths feed on a wide variety of trees, including apples, birches, black locusts, cherries, elms, firs, hackberries, hemlocks, hickories, larches, oaks, roses, spruces, chestnuts, and willows.

Adult moths and their caterpillars are essential links in the garden food web.  Not only are moth larvae the principal food of summer song birds, they are the principal prey of many predatory insects, including hoverflies, wasps, and beetles, insects that keep garden herbivore populations at tolerable levels.  Many gardeners who spend time in the garden looking for caterpillars find them among the most beautiful of garden creatures.

Sustaining a garden that supports wildlife, including caterpillars, takes a lifetime.  The job is never done and the learning never stops.  Each garden season brings new discoveries, new species to add to your ever-growing list of garden life, and new efforts to strengthen the ties that bind species together in the ecosystem we call the garden.

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About Reeser Manley

I was born in Laramie Wyoming but moved to the southeast at an early age. I was educated through my B.S. in Biology in the Columbus, Georgia area, then crossed the Chattahoochee River to earn my M.S. in Botany at Auburn University. For the next ten years, I worked as Horticultural Manager for the George W. Park Seed Co. in Greenwood, S.C. At 40 years of age, I decided to return to graduate school and in 1994, I earned a Ph.D. in Horticultural Science from Washington State University, Pullman, Washington. Fast forward through 10 years at university (7 at UMaine, Orono) and you find me teaching high school science in Eastport, Maine, the edge of the world, and writing a weekly garden column for the Bangor Daily News. My new book, The New England Gardener's Year, a Month-by-Month Guide for Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, and Upstate New York”, will be published later this year by Cadent Publishing. You can learn more about the book by visiting its Facebook page: http://www.facebook.com/pages/The-New-England-Gardeners-Year/187285218055676.)