Summer is peak butterfly season with warm, sunny weather that sends colorful sulphurs, monarchs and swallowtails flitting through our gardens. But you might be surprised to know that there’s some significant butterfly activity in every season. Take a look at what you might expect to see throughout the year.
Spring: Welcome, Butterflies
In the southernmost U.S., winter fades almost imperceptibly into spring. Elsewhere, however, particular species are sure signs of springtime. Among these are small white butterflies like West Virginia and spring whites, and various types of orangetips and marbles. Their caterpillars feed on wild plants in the mustard family, which grow mainly in spring. The adult butterflies must emerge early so females can lay eggs and the caterpillars can feed while the plants are available.
Other spring specialties include certain tiny blue butterflies, like the spring azure and the silvery blue. These little gems may show up in gardens or gather by the dozens around the edges of mud puddles. Less noticeable are some small, dark hairstreaks and skippers – somewhat obscure, but worth seeking out for their poetic names, like frosted elfin and sleepy duskywing. But no one is likely to overlook some of the big swallowtails that start flying early in the season, such as the gorgeous streamer-winged zebra swallowtail.
Early in spring, monarchs that have wintered in Mexico begin to move north. A few others—red admirals, painted ladies and American ladies among them—are on the move, too. In the Southwest, tens of thousands of painted ladies may join in a mass flight, flooding into gardens along their path. Week by week, new nonmigratory species emerge. Bright sulphurs, subtle satyrs, flashy fritillaries and others add to the color palette that will grace summer gardens.
Summer: Beauty at Its Peak
A large and diverse garden is often alive with butterflies all summer long. Casual observers may think they’re seeing the same ones over and over, but the reality is more complicated and more interesting. Most adult butterflies live two to three weeks at most. With common small species like pearl crescents and tailed blues, the first females to emerge in spring or early summer lay eggs that will soon hatch. The caterpillars will grow rapidly and pupate, and another batch of adults will appear; there may be three or more generations in the warm months.
Shorter summers often mean fewer generations. Several species, including some of the swallowtails, may have several broods a year in the Deep South but only one in the North. And some, including the great spangled fritillary, have a single generation each year regardless of latitude. Of course, summer is also when many migratory southern species push northward. Tropical sulphurs and skippers fly from Mexico into the American Southwest; widespread butterflies like buckeyes and red admirals may reach up beyond the Great Lakes. By summer’s end, migratory monarchs have reached the northern U.S. and far into Canada, poised for the temperature drop that will send them drifting south again.
In Alaska and Arctic Canada, a few butterflies – mostly lesser fritillaries and satyrs – fly only every other year. Summers are so short that the caterpillars hatch in one season, hibernate through one winter, feed and grow through the following summer, and then hibernate through a second winter before pupating and emerging as adults in their second summer. That’s why a species can be common one summer and seemingly absent the next.
Fall: Winding Down
Most adult butterflies will perish before winter arrives. Long before the intense cold sets in, the females will have laid eggs, ensuring a new generation for the next year. With that taken care of, the adults may spend the rest of their short lives wandering in a seemingly aimless way.
But some species do live through the winter, hibernating in sheltered sites, and they may be seeking out these roosting spots as fall advances. Mourning cloaks, question marks, commas and tortoiseshells are among these hibernators, so if you see them flitting about woodpiles or tree cavities in fall, they are likely looking for winter shelter.
A few varieties fly only in late summer and fall. The red-bordered satyr, which makes its rather floppy way through Southwestern canyons in September, is one; another is Leonard’s skipper, a denizen of Northeastern meadows. Few of these show up in gardens, however; most of what you’ll see in your backyard is a continuation of summer habits, like the northern push of southern species. Subtropical creatures like big pale cloudless sulphurs and tiny orange fiery skippers may still be heading north in early October, even filtering into southern Canada.
Winter: Hiding Out
Along the Gulf of Mexico, in the lowlands of the desert Southwest and on California’s coast, mild winters allow some butterflies to keep flying. They may be out of sight on cool, cloudy days, but red admirals, painted ladies and others fly in warmth. East of the Rockies, most monarchs are absent, having flown to Mexico. But much of the Western population spends the season in coastal California. They are sedentary, hanging in dense clusters in tall trees. On warm days, they’ll scatter to the wind like orange confetti, drifting back to the roost as evening nears.
Relatively few other species migrate, surviving the cold months in any of their four major life stages. A few tough butterflies hibernate as adults; a February thaw may wake them, producing the startling sight of a mourning cloak, comma or tortoiseshell flying over snowdrifts. Some swallowtails and others spend the winter as pupae, ready to emerge as adults in spring. Still others overwinter in the egg stage. Caterpillars might seem more vulnerable, but the majority of our butterflies spend the winter in that form. They may even hatch out of the egg in fall and not begin to eat until spring. So even when northern regions are locked in ice and snow, next summer’s butterflies take the shape of myriad tiny caterpillars sleeping in the cold.
Identifying Butterflies: Grab a field guide and ask yourself these questions when you see an unfamiliar butterfly.
- SIZE: How many inches is the wingspan?
- SHAPE: Is there a tail? Are the wings jagged or scalloped?
- POSTURE: How is it sitting? Wings folded up tight, spread wide, or half open in a V shape?
- FLIGHT STYLE: Is it flying with steady flaps, a quick flutter or completely erratically?
- FIELD MARKS: Is there a spot of color?