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The Tortoiseshell Butterfly: Trust us, they're not monarchs


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I have a good friend, Alex Weiss, who is a world-class builder, finish carpenter and poet with whom I share good feelings about the nature of our grand old planet Earth. He and I shared an evening together with Friends of the Sunriver Nature Center last week - Alex reading poetry about coyotes, me telling stories about coyotes and everyone really enjoying the foot-stomping, toe-tapping music of Cinder Blue, a splendid musical group out of Redmond.

Alex strayed from coyotes a couple of times and read some of his delightful poems about other facets of nature. When he laid one on me about tortoiseshell butterflies, he hit my soft spot:


A new home under construction

the doors open most of the time,

easy transit for everybody,

including a few butterflies.

Sometimes I come in at morning

and find them colorless on the floor,

other times I find them wings flapping

at a window, confused by glass.

When I can, I catch them very gently,

bring them over to a door, and let them go.

Sometimes I do this with moths, even flies.

Something about their effort

strikes me deep.

Hungry for light and warmth, constrained

by forms beyond conception, pushing

until death and/or freedom,

I say thank you

for the hands that help, beyond my grasp.

Alex Weiss - 2010

The California tortoiseshell butterfly, known to the scientific community as Nymphalis californica, is that unlikely orange-and-black butterfly you see fluttering about on warm days in winter. Some people think it's a monarch, but it's not - monarchs are tropical butterflies that winter either in Mexico or along the California coast. The tortoiseshell is an all-season butterfly that can survive the winter as an adult in our backyard, no matter how cold it gets because their "blood" (if you want to call it that) has "anti-freeze" in it.

With this special adaptation, it can hide behind a stack of old boards, under the porch, or clinging to the underside of downed logs covered by a blanket of snow (which actually insulates them) and the colder it gets, the better their anti-freeze works.

Those of us who burn wood to keep warm throughout the winter often disturb a tortoiseshell or two hibernating in the wood stack when we bring in wood to feed our stoves. Livestock owners, going into barns to throw down bails of hay for horses, sometimes disturb a tortoiseshell that was trying to stay out of harm's way snuggled up against a bale of hay for winter.

A disturbance in winter, however, doesn't mean the end for this tough little insect. If the sun is shining, it can gather just enough warmth to get its flight muscles moving and flutter off to a new hiding spot.

In my memory, we have never had the enormous populations of tortoiseshells we have with us at this time - the last big outbreak I recall was in the mid-1980s. My wife, Sue, was conducting butterfly counts around Bend when we ran into thousands and thousands of tortoiseshells mating and laying eggs on ceanothus (snowbrush) up near the end of Skyliners Road and Tumalo Falls, west of Bend.

When the eggs hatched, the larvae defoliated thousands of acres of ceanothus and when they went into the chrysalis stage, there were, literally, millions of them hanging on the lower branches of the defoliated snowbrush.

I can recall the extraordinary results of disturbing the chrysalides. I was walking past a large group hanging under an especially robust ceanothus when I stubbed my toe and stumbled. The act of stomping my feet set off a ringing noise all around me. When I looked for the source, I could see thousands of black, hanging tortoiseshell chrysalides vibrating - the source of the bell-like ringing.

Not all of the millions of chrysalides, however, were destined to be butterflies. Hundreds of thousands were devoured by golden-mantled ground squirrels, pine chipmunks, birds and a variety of insect parasites.

In an effort to photograph the emerging butterfly, we returned home with about 10 chrysalides. I was quite surprised not to see the expected butterfly emerging from the chrysalides, but instead 10 or 15 tiny, metallic adult wasps.

When the caterpillar was about to enter the chrysalis stage, the female wasp laid her eggs inside the caterpillar. When the chrysalis was finished, it became the nursery for the wasp larvae that fed on the metamorphosing butterfly. The timing was perfect!

And speaking of metamorphosis - to me, that is the most astounding process of nature. The last instar the caterpillar experiences caused it to create a case (the chrysalis wall) that will fit the adult insect's wings and body. It doesn't really "die" as we know death to be, but rather breaks down into a chemical soup - the spark of "life" still there - and then the biological soup begins the process of creating the adult insect.

The orange and black color scheme of the adult tortoiseshell provides it with protection like that of the awful-tasting Monarch butterfly. The colors spell out bad stuff to predators such as birds, but parasites are not bothered by taste and devour them at every opportunity.

About five years ago, the present tortoiseshell outbreak we're enjoying began in Yosemite National Park. For some unknown reason, thousands of tortoiseshells began to multiply in and around the park. They began drifting northward all summer and within three years, the growing numbers of butterflies reached the Northwest. The population is still growing. Why? Who knows - climate change seems to be a good whipping post for such events we don't understand, so let's leave it at that for now...

Also, there's a look-alike that can fool you, called Milbert's Tortoiseshell. It's just as pretty, but they're not in the numbers of their brethren... yet!

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