By Jody Sackett
Butterflies are beloved. Some folks consider these beautiful pollinators messengers from heaven, although, more realistically, they are a sensitive indicator species that reveals the health of their ecosystem.
While we typically think of them as warm-weather insects, it’s even more fascinating to watch these cold-blooded creatures in autumn as they prepare in different ways for the coming winter. That’s why fall is a favorite time for “butterfliers,” nature lovers who seek them out. Unfortunately, butterfly populations in New Jersey, as in the rest of the country, have been declining due to factors such as habitat loss, pesticide and herbicide use, and lack of native plants. We can help them in simple ways, by planting native flowers and raising butterflies at home.
A Butterfly’s Life
There are 130 species of butterflies in New Jersey, including the vibrant monarch, the gorgeous fritillary, the speckled painted lady, the unusual question mark, and our state butterfly, the enchanting black swallowtail. They are all members of the Lepidoptera order, and share the same basic life cycle: eggs hatch to caterpillars (larvae), which pupate in a cocoon-like chrysalis and emerge as flying adults.
But it’s a delicate dance right from the start. Using taste sensors in their feet, adults lay eggs on or near specific host plants that have co-evolved with the butterfly, so the newly-hatched caterpillars will immediately have the proper food. Monarchs, for example, eat only milkweed, since it provides all the nutrients and lipids needed, and the bitter toxins render the caterpillars and adults inedible to predators. Sometimes species are picky eaters as larvae; specialist species, such as the monarch and the large hackberry emperor, which likes hackberry trees, cannot switch food sources any more than humans could start living off tree bark. But generalist species, like the swallowtail and painted lady, can tolerate multiple host plants.
Sometimes adults are the picky eaters; the mourning cloak and question mark butterflies prefer tree sap, partly because it contains more proteins, lipids and minerals than nectar.
These unique requirements are why native plants are so essential to healthy butterfly populations.
Butterflies inadvertently pollinate flowers as they feed, transferring male pollen from one flower into the ovary of another. Once pollinated, seeds can develop. Flowers, whose goal in life is to be pollinated as much as possible and take over the world, have evolved unique strategies to attract specific butterfly pollinators and achieve this goal. Many flowers are brightly colored to attract butterflies and bloom in the warmer daytime when these cold-blooded insects are most active.
Butterflies also need easy-access tubular flowers to accommodate their straw-like proboscis for sucking nectar, as well as “landing pad” petals they can grab with their feet while they slowly feed. Flowers like phlox, cardinal flower and purple coneflowers happily provide this. Other clever flowers have become the Starbucks of the ecosystem, offering nectar with a high sugar content (Joe-Pye weed, asters, blazing star) or opening up early in the season for nectaring and staying open late (goldenrods).
Trees and flowers may also coordinate their blooming times for pollinators and sometimes timing is everything. Mourning cloak and question mark butterflies, which overwinter as adults, become active during the first warm days of early spring before most flowers start blooming. Luckily for them, tree sap also starts running on those early warm days, providing sustenance for these hungry butterflies who will hang around to pollinate the oaks, maples and willows.
Most flowers bloom in summer, when butterfly populations peak and the demand for nectar is high. While late fall bloomers miss this peak, it also means they have less competition for pollinators.
Like Starbucks, flowers can occasionally run out of product, so prodigious nectar producers like milkweeds, asters and goldenrods are necessary. It’s no coincidence that milkweed exceeds nectar expectations in fall, when the mighty monarchs on their 3,000-mile migration from New Jersey to the oyamel fir forests in the central Mexican mountains need high-sugar meals all along the way.
The Butterflies’ Decline
Yet despite these effective tactics, butterfly populations are still declining. Why? Like most things in life, there are multiple reasons. As human populations spread, development expands into what were once vast sources of habitat and food, substituting actual coffee shops, retail establishments, restaurants and homes for fields of native trees and flowers.
Local herbicide use can unintentionally cause collateral damage, as it can kill both weeds and nearby beneficial plants, like the lowly lawn clover that provides nectar. Pesticides sprayed to control bugs like mosquitoes or ants will often kill whatever they land on, including caterpillars and butterflies.
Climate change results in hotter summers and droughts or floods. These new seasonal conditions can cause plants to flower earlier, later or not at all, creating a mismatch that no longer coordinates with long-established pollinator life cycles. Imagine the poor monarchs migrating along the same route every year, discovering that many of the feeding rest stops are abruptly closed.
How to Help
Native plants, which have evolved in tandem with butterflies over centuries, are essential to maintaining healthy populations. They will leaf out at the right time, bloom at the right time, and provide nectar at the right time. Planting natives is probably the most important and easiest thing we can do to help butterfly populations.
Dedicate a corner of your backyard, an unused side yard, or even just patio pots to be your Butterfly Patch. Plant host natives there, like milkweed (butterfly weed is pot-sized with gorgeous orange flowers), Zizia or golden Alexanders and spicebush. Avoid hybrids, which may be quite different from native versions and unhappily produce different nectar and pollen. Trees and flowers are also essential for sap and nectar, so strive for tulip, sassafras, birch or willow trees if you have room; add JoePye weed, coneflowers, goldenrod, bee balm, asters, and blazing star for nectar. Your yard will look lovely and, if you plant it, the butterflies will come.
Don’t chase them away by using herbicides or pesticides, or at least don’t use these chemicals anywhere near your Butterfly Patch. Leave shrubs around for sheltered hiding places, some open sunny areas with flat rocks for sunbathing and a shallow dish of drinking water.
Since eggs and caterpillars overwinter in dead leaf litter and plant stalks, keep this stuff around until spring for them.
Finally, you can become a butterfly “farmer” this autumn. All you need is an inexpensive zippered net cage (sold online) or old plastic container, a sturdy small vase or bottle, and some Lepidoptera love. Butterflies usually lay their eggs on the underside of their host plants, just one little whitish egg at a time. Lots of predators like to eat these, but if you rescue the eggs and raise them to adulthood, there will be more butterflies around.
With cold weather coming, these autumn butterflies will be overwintering in a diapause (dormant) stage in one of four ways: as eggs (fritillaries), as caterpillars hidden in leaf litter or woodpiles (wolly bears and viceroys), as chrysalises attached to branches (swallowtails) or as adults (mourning cloaks hidden in tree bark crevices).
Since swallowtails easily overwinter in New Jersey as chrysalises, here’s how to see them through to spring:
• Place paper towels on the floor of your butterfly cage for easy cleanups. Happy caterpillars will produce copious little balls of poop (“frass”) that drop onto the paper towels.
• Place two to three large bottlecaps on the cage floor and fill with water.
• Find newly-laid swallowtail eggs on host plants like parsley, fennel, dill and Zizia. Carefully remove the leaf or branch by its stem without disturbing the egg. If you find baby caterpillars instead of eggs, put those in your cage.
• Put the stem in a small bottle with water to keep it fresh. When caterpillars hatch, they’re voracious eaters and will need lots of fresh leaves. Remove eaten leaves and put fresh ones in regularly. Swallowtail caterpillars will molt five times as they grow, splitting their cuticle skin and crawling out of it (they’ll also eat the shedded skin).
• Caterpillars stop eating when they’re ready to pupate, so now’s the time to put some small tree branches in your cage. The caterpillars will attach themselves upside-down to the branches, form a “J” shape, molt one last time, and spin a thread “girdle” attaching their midsections to the branch. Miraculously, the caterpillar soon becomes a bumpy green chrysalis that turns brown to camouflage it from predators.
• Your caterpillar-in-a-chrysalis will remain dormant until spring and, until then, needs to be left protected and undisturbed in an unheated place like your garage or outdoor shed. Warmer temperatures trigger hatching, so start checking on them in April. When the butterfly hatches as a brand-new adult, give it a day to stretch out wrinkly new wings and pump blood into them. You can feed the butterfly a slice of orange or a small amount of Gatorade in a bottle cap. Release the butterflies near the plant you found the egg on, and watch them happily fly away to nectar and lay more eggs.
• You can repeat this process in spring with more swallowtail eggs, or try monarch eggs found on milkweed leaves. However, remember that summer butterflies will hatch and fly away, and won’t overwinter like the fall ones do.
For more information about butterflies, check out the New Jersey Butterfly Club’s website at njbutterflies.org. The Jersey-Friendly Yards website (jerseyyards.org) has outstanding native plant resources tailored to your butterfly needs. And apps like iNaturalist love to have citizen scientists assist them in collecting helpful New Jersey butterfly data. The butterflies will thank you.
The article originally appeared in the September 11 – September 17, 2025 print edition of The Two River Times.
