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The little rust-colored butterflies you may have been seeing in great abundance lately are European skippers. Photo by Emily Stone.
It was like something out of a fairytale. Hundreds of tiny orange butterflies rose up in waves before me as I walked down the grassy path. Each fluttered delicately for a moment before sinking back to rest on the green blades, the lupine leaves, and almost every surface in the community garden.
Later, after photographing chickadee parents at a friends’ house, I spotted more clouds of the rust-colored sprites twinkling among the needles of a spruce tree where mowed lawn met meadow edge. Other friends report similar flocks of orange.
And then, in the museum’s pollinator garden, I was able to creep up on one who had perched on the sunny yellow center of a coreopsis flower. Rusty orange was the dominant color, but a dark border around their wing margins streamed inward along veins in an elegant pattern of scallops. A cream-colored fringe decorated the trailing edge of the wings. And, for such a small butterfly, their body was surprisingly plump and furry – a characteristic of the Skipper Family to which they belong.
Their name, however, gives them away as an interloper. European skippers are native to many places – Europe, Scandinavia, North Africa, and Central Asia – but they aren’t native here. They were introduced to the United Kingdom in 1889, and to London, Ontario, in 1910. They now range across the Northeastern United States, and into a group of western states as well.
As I observed in the community garden, this cosmopolitan species can be astonishing in their local, short-term abundance. The museum is conducting butterfly surveys in our pollinator gardens as part of a Statewide Community Science Project with the Milwaukee Public Museum. On one 15-minute survey in late June, museum interns counted 35 European skippers and not a single other species of butterfly. A few days later, a handful of species showed up one at a time, but the count of skippers was still the 20s.
If you watch closely, you might notice some of the skippers flying low over grassy areas with a seemingly nonchalant, wandering pattern. These are the males, searching for receptive females. Once mated, females lay a string of about 30 greenish-yellow eggs on the stem of a grass. Those fragile dots survive the winter. This is the only member of the Skipper Family to overwinter in the egg stage. Others endure the cold as caterpillars or in a chrysalis.
This habit, of being inconspicuous and durable on blades of grass, is likely how European skippers have become such world travelers. Back before the days of packing peanuts or bubble wrap, fragile items like ceramics were packed in dried grass. That’s probably how they first arrived in Ontario. Since then, they’ve been moving around within the continent, too. One study found more than 5,000 European skipper eggs in a single bale of timothy hay – another introduced species. Ship that around for rabbit food or cattle fodder and suddenly you have clouds of rusty orange butterflies in lots of new places.
Starting in mid-May, the eggs hatch, and green caterpillars eat the tender young shoots of grass. Where abundant, the caterpillars can strip entire stalks bare, and eat the mini-cattail-like seedheads, too. When ready to pupate, they sew a shelter out of leaves and silk and metamorphose into an adult butterfly.
The short-term abundance of the European skipper we’ve been seeing for the past couple of weeks is partly due to the phenology of their life cycle. All of the butterflies emerge, feed and lay eggs just once per summer, and all about the same time. Their incredible numbers are also related to their status as a non-native species. The European skipper has few natural predators or parasites to control populations on this continent, and so can reproduce unchecked by feeding on another abundant, introduced species – timothy grass.
As with any introduced species, there is the danger that the newbie might compete with native species or otherwise disrupt an ecosystem. It’s possible that European skipper adults are reducing the nectar availability for other butterflies. And if you grow timothy hay, you might be unhappy with an infestation of the caterpillars. Unexpectedly, showy lady slipper orchids might be the biggest loser.
The orchid’s game is to trick bumblebees into wallowing around their pink pouch in search of (non-existent) nectar while surreptitiously attaching pollen to the bees’ hairs. When European skippers enter the pouch in search of nectar, they get trapped and die. Their bodies take up so much space that the actual pollinators can’t enter. Pollination fails, and there can be little to no seed production.
It’s unclear if this is a widespread problem. On a recent foray to see showy lady slipper orchids in a fen, I don’t recall seeing a single European skipper. The fen habitat is just too unique and too intact to support the non-native grasses their caterpillars prefer, and the butterflies don’t stray far from the host plants where they need to lay their eggs…I hope.
So, as you walk through tall grass and clouds of little rust-colored sprites fly up around you, take a minute to appreciate the world-traveling European skipper. Who knew there was such a big story behind this tiny butterfly?
Emily Stone is Naturalist/Education Director at the Cable Natural History Museum. Her award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at cablemuseum.org/books and at your local independent bookstore, too. For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is now open with our exciting Growing Up WILD exhibit. Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.