From where do the springtime butterflies come?

You likely learned in grade school, from Heimlich in a Bug’s Life, or from the Very Hungry Caterpillar, that every butterfly undergoes metamorphosis. For all butterflies, this phenomenon involves four distinct stages of development. An individual starts as an egg, breaks out as a caterpillar (or larva), eats leaves until it’s ready to pupate into a chrysalis, and subsequently emerges as an adult butterfly. Adults fly around to mate, feed on flower nectar, and produce the next generation. A successful butterfly not only has to make the transition from egg to larva, pupa, and eventually adult, but in New England, also has to endure six months of cold, harsh conditions. So how do such delicate creatures make it through the winter?

Well, the answer depends on which of New England’s 100+ species of butterflies we consider!

Some butterflies spend the winter as small, immobile, and defenseless eggs. Once such species is the bog copper Lycaena epixanthe which thrives in undisturbed cranberry bogs of New England such as those found on Cape Cod. Adults lay eggs on the bottom of cranberry leaves near the surface of the bog. These eggs are built to withstand not only winter freezes and thaws, but also periodic flooding. Caterpillars break out of their eggs in the spring and begin chowing down on cranberry leaves,  their favorite food. Other gossamer-wing butterflies like Coral Hairstreak Satyrium titus and Oak Hairstreak Satyrium favonius spend the winter as eggs on their favorite trees, black cherry (Prunus serotina) and oaks (Quercus spp.), respectively. Eggs are situated safely in the crevasses of the tree bark and branches, at the roots of the tree, or in the leaf litter surrounding it.

Great Spangled Fritillary. PC: Nick Dorian

The majority of butterflies spend the winter as caterpillars. Typically, these species begin feeding as caterpillars before winter to amass nutrients and fat for the long dormancy ahead. Then, when the weather cools, they find someplace safe from the elements, often underground or in the leaf litter. Other species like Viceroy Limenitis Archippus build their own houses for winter, known as hibernacula, by twirling poplar or willow leaves using silk. Not all species go about it this way though; the Great Spangled Fritillary Speyeria cybele, spends its winter as an unfed larva so that its life cycle is timed with the availability of violets.

Eastern Tiger Swallowtail. PC: Nick Dorian

Then there are species that spend the winter as a chrysalis. In this intermediary stage between caterpillar and adult, the butterfly completely reorients its body and restructures itself. The chrysalis is a very hardy life stage, which is why all swallowtail butterflies (Papilionidae) spend the winter in this form. Black swallowtails Papilio polyxenes, like many of their relatives, affix their chrysalises to a tree’s bark or branch, held in place by a thin, but strong, thread of silk. Often these dormant individuals will cryptically blend in with the branch or the leaf on which they’re placed. The Canadian tiger swallowtail Papilio canadensis, withstands the winter cold by amassing high concentrations of ethylene glycol in the chrysalis. This compound is such an effective cryoprotectant that it’s the base compound for commercially manufactured antifreeze.

Mourning Cloak. PC: Max McCarthy

Although some butterflies do overwinter as adults in New England, it’s a rare strategy. The most readily seen of these species is the Mourning cloak Nymphalis antiopa. The Mourning cloak is often the first butterfly seen in the year, coming out before snow has fully melted, and even capable of coming out on particularly warm winter days to sun. This is because it has a high concentration of glycerol, another cryoprotectant, which makes it difficult for damaging ice crystals to form in its body. The Eastern Comma Polygonia comma and Question Mark Polygonia interrogationis are two other species which also have the capacity to withstand cold New England winters. These remarkable butterflies will find crevasses in trees, beneath bark, or under rocks and buildings where they will be ready and waiting for the earliest signs of spring to emerge and mate.

And last, but not least, there are also butterflies that choose to avoid the bad weather entirely! There are only two species of migratory butterflies found in New England, which leave for the winter and come back for next year’s spring or summer. The Monarch Danaus plexippus butterfly heads south to the warmer climes of Mexico, where millions of butterflies will gather in massive aggregations in oak-pine forests. The Painted lady Vanessa cardui is another long-distance migrant, though its journey is less directed than that of the Monarch. In Europe, the species is known to embark on transcontinental migrations from the northern parts of Europe to the Sahara Desert. The details of its journey in the eastern United States remains to be known.

The diversity of overwintering approaches among butterflies demonstrates the capacity of small insects to adapt in hostile environments. When you see your first butterfly of the year, consider how they might have managed to make it outside while we’re spending time by the fireplace with hot cocoa. You also might think twice about cleaning up your leaves until the beginning of summer to give butterflies who overwinter there a chance to emerge! For other tips on supporting butterflies and other pollinators, check out our January blog post!

Five easy ways to support pollinators in 2021

2020 was a rough year for everyone, including pollinators. Asian giant hornets arrived in Washington state, threatening honey bees; western Monarch butterfly numbers were the lowest in the past 30 years; neonicotinoid pesticides continue to be approved for use in the United States; and endangered rusty-patched bumble bees did not receive critical habitat because their biology is too poorly understood. That’s just the start.

Pollinators face a relentless barrage of threats from humans. The main factors driving pollinators declines include habitat loss, pesticides, climate change, light pollution, and the spread of exotic species and disease. Recently, scientists framed pollinator declines as “death by a thousand cuts,” underscoring that no single factor is solely responsible. Rather, the combination of multiple factors working in tandem is the greatest threat.

With this in mind, 2021 is a perfect year to resolve to make a small change in your lifestyle to support pollinators. Inspired by a recent list of actions to conserve insects, TPI proposes five actions you can take in 2021 to make a difference in the lives of urban pollinators:

1. Grow native plants. Native plants are beautiful and adapted to the local environment, meaning they require less water and fewer chemical inputs compared to ornamental plants. Even more, they offer food (pollen, nectar, leaves), nesting sites, and shelter for pollinators. Native plants also provide cultural benefits in the form of reconnecting community members to their local environments. Interested in growing natives? Check out our native planting guides and stay tuned for details regarding TPI’s native plant sale during 2021 national pollinator week.

Plant native goldenrod to assist eastern Monarch butterflies on their fall migration to Mexico.

2. Reduce your pesticide use. Pesticides are nasty chemicals that are widely used to suppress pest insects and weeds, but also cause non-target effects in pollinators. In spite of successful efforts in Europe to increase regulation on these pesticides, as well as ongoing campaigns here in the U.S., many harmful chemicals remain available to consumers worldwide. On average, lawns receive ten times more pesticides than do conventionally grown crops. Use pesticides judiciously and in a targeted way; avoid broad applications and claims by companies to “eradicate mosquitos.” Remember: any product that kills a mosquito also kills a bee.

3. Turn off your lights at night. Artificial light at night (ALAN) is one of most recognizable signatures of humanity from space. Yet, it also spells disaster for nocturnal pollinating insects like moths and beetles. Insects attracted to lights are easily picked off by predators and are worse at finding mates. As a result, insect populations suffer in areas with high ALAN such as cities. To curb declines of nocturnal pollinating insects, install motion-activated lights, replace bright blue-white lights with softer red-orange ones, or plant a moon garden containing night-blooming plants. Let’s keep our skies dark.

4. Shop local and support farmer’s markets. Many growers and vendors in Somerville and Medford near Tufts University (like the Somerville Winter Market and Neighborhood Produce) are committed to supporting pollinators by selling pesticide-free, locally-made products. Shop there as often as possible in order to avoid less insect-friendly alternatives at larger chain stores.

5. Educate others and share this post. Urban pollinator conservation depends on the active participation of the community. Become an advocate for pollinator conservation by writing to your politicians, installing a yard sign, or by simply talking about it—to your kids, your friends, your neighbors, your hairdressers, your bakers, your baristas. Teach them that bees come in all shapes and sizes or challenge them to notice their first monarch butterfly of the year. Simple awareness of pollinators—getting people to notice their environment—is the goal.

Have you made any pollinator resolutions for 2021? Let us know! We’d love to hear from you.

Urban Boston Fall Pollinator BioBlitz!

This weekend, September 26-27, 2020, join TPI for a fall pollinator bioblitz! If you live in the city around Boston (east of I-95) get out during the weekend to observe pollinators—bees, butterflies, hover flies, wasps, and beetles—and post your sightings to iNaturalist. There will be so many insects to see, including monarch butterflies, bumble bees, paper wasps, goldenrod beetles, and more! If you’re not familiar with iNaturalist, see this guide for getting started.

During the bioblitz, TPI biologists will be scouring the flowers in our gardens on the Tufts University Medford-Somerville campus. We hope you’ll get out in your yard or neighborhood to look for pollinating insects, too. Your participation in this bioblitz will help TPI biologist better understand how gardens support pollinators in the city.

Never participated in a bioblitz before? Here are some tips to get you started: