The Lowdown on Lepidoptera
Butterflies and Moths
Is there anything more rewarding than butterflies in the garden? It’s as though some blossoms have taken wing. Or fairies have come to life. A touch of magic.
Compared to bumble bees, which get themselves into situations like this ⬇️, the butterfly vibe brings to mind sleek models on the catwalk.
Moths are pretty glamorous, too. For a minute of astonishment, watch this short video on – of all things – moth wing flaps:
What’s The Difference Between a Butterfly and a Moth, Anyway?
About 180,000 species of butterflies and moths make up the order Lepidoptera. They have a lot in common, but here’s how to tell them apart:
Butterflies are colorful, while moths dress in more subdued hues.
Butterflies hold their wings up when they rest; moths hold them down.
Butterflies have thin antennae ending in a little knob; moths tend to have more feathery and dramatic ones, perhaps to make up for the color deficit.
Butterflies have thin bodies; moths have a thicker girth.
Butterflies fly during the day; moths are nocturnal.
(I know, I know. There are exceptions to these rules. Don’t come at me with your pistachio-green luna moths.)
Life Cycle
Monarch butterflies are unusual in that they migrate back and forth between North and Central America each year, which is a whole amazing story unto itself. Most other lepidoptera live out their lives in one place. This might sound boring, but don't worry: with all that metamorphosis going on, they get plenty of excitement, too.
Butterflies and moths begin life as eggs laid on or near a plant. They hatch as tiny, soft-bodied caterpillars, whose job is to eat as much of that plant as they can in a short period. Crucially, the vast majority of caterpillars are diet specialists, meaning they can eat only one kind of plant. A pregnant female will thus lay eggs only on those species. Monarchs and milkweeds are a famous pairing. But almost every other butterfly and moth has its “own” larval host plant, without which it won’t reproduce.
Once caterpillars have sufficiently stuffed themselves with their host plants, they form into pupae or chrysalises. Sometimes these hang from branches or other structures. Many species, though, just drop from their host plants down to the ground to pupate among the duff and leaf litter. During this stage, the caterpillar completely reinvents itself, eventually emerging from the cocoon as a winged adult.
Not Just a Pretty Wing
Beyond their beauty, lepidoptera are a critical node in the food webs that keep us humans safe, healthy and alive.
Insects are the animals that are best at transferring energy from plants to other animals. Among insects, lepidoptera play a key role because their caterpillars are a diet mainstay for most North American birds, especially when they’re raising chicks. Unlike say, a crunchy beetle, caterpillars are squishy and nutritious – easy to stuff down the gullet of a hungry nestling. Small mammals, amphibians and reptiles also appreciate having fresh caterpillars on the menu.
In addition, lepidoptera are of course known for their pollinating skills. Pollinators are responsible for helping more than 80 percent of the world's flowering plants reproduce. That's huge! Remember, many of those flowers belong to foods we eat and plants that sequester the carbon we emit and floodwaters we unleash, to name just a few human-sustaining functions.
Extinction Risks
You’ve probably heard by now that many moths and butterflies are threatened. Of the 800 species here in the US, 19 percent are currently at risk of extinction. Five have earned that terrible distinction since 1950. The plight of monarch butterflies is perhaps the most well-known. They’ve declined 85 percent in two decades. The western population, which overwinters in California, has seen a 99 percent decline. Overall the migrating populations are less than half the size they need to be to avoid extinction. They’re being decimated by pesticides, habitat loss, invasive plants and climate change. In other words, by us.
The flip side of this depressing coin is that there’s plenty each of us can do to reverse some of the damage. The trick is to provide habitat for them throughout their life cycles.
Do’s and Don’ts for Supporting Butterflies
Do plant native trees, shrubs and perennials with overlapping bloom times from early spring through fall. Use the National Wildlife Federation’s “Find Butterflies” tool to figure out which plants are best suited for your zip code.
Don't plant hybrids, especially those with "double" flowers or dramatically altered blossom or leaf colors. Horticulturists propagate hybrids to please plant-buying humans, but in the process they often breed out the nectar, pollen, or fragrance, or so alter the shape of the flowers that the pollen and nectar become inaccessible to pollinators.
Don't plant butterfly bush (Buddleia species) or other non-native plants, even though they may be misleadingly marketed as "butterfly-friendly." Butterfly bush nectar apparently tastes great. But as far as nutrition goes, you might as well be serving up Mountain Dew and Cheez Doodles to marathoners. Those pretty shrubs just don't provide the nutrients butterflies need, and may therefore contribute to their early deaths and failure to reproduce. Plus they're invasive, so they crowd out the plants that are actually nutritious.
Do plant larval host species in addition to nectar providers. Our flying friends need to reproduce as well as eat. That NWF tool will help you match lepidoptera to their hosts. Note that native plants support 35 times more caterpillar biomass than non-natives do.
Don’t use pesticides. Your target may be mosquitoes or aphids, but you’ll kill butterflies – and many other beneficial species – while you’re at it.
Don’t buy plants that already contain pesticides. Many nurseries just routinely treat their plants – even those they label as pollinator-friendly – with pesticides. This makes them deadly to the insects they’re meant to befriend. Before you buy, ask whether pesticides have been used at any stage. If so, shop elsewhere – ideally at a nursery that specializes in native plants and uses organic methods.
Do create “soft landings” for dropping cocoons under trees, particularly those known to support lots of caterpillars (check that NWF site to find out what those are). The best soft landings include native groundcovers and fallen leaves that have been left to decompose over the winter. Leave those leaves!
Do turn off outdoor lights at night. Those pretty up-lights in your crape myrtles disorient and exhaust moths.
Don’t focus on butterflies to the exclusion of other pollinators. What we need is healthy, biodiverse ecosystems – not just isolated butterfly sanctuaries.
I know you’ve been wondering, so I asked around and now have it on good authority that this is the lepidoptera anthem:
Resources
Christopher A. Halsch, et al, “Milkweed Plants Bought at Nurseries Expose Monarch Caterpillars to Harmful Pesticide Residues,” ScienceDirect, September 2022.
Doug Tallamy, Bringing Nature Home, Timber Press, Portland, OR, 2007.
Doug Tallamy, Nature’s Best Hope, Timber Press, Portland, OR, 2019.
“Butterfly Conservation,” Xerces Society.
“Caterpillars, Butterflies and Bees,” Pollinator Pathway.
“Gardening for Pollinators,” U.S. Forest Service.
“Monarch Butterfly,” Center for Biological Diversity.
“Monarch Butterfly Migration and Overwintering,” U.S. Forest Service.
“Pollinators,” U.S. Forest Service.
“Who Are the Pollinators?” Xerces Society.