Invasion of the tortoiseshells

The phone at the Anderson home has been ringing off the hook and almost every caller is asking the same question: "What are all those orange and black butterflies?"

What indeed? They are California Tortoiseshells, known to the Lepidopterist community as Nymphalis californica - and we're seeing only a tiny fraction of the uncountable millions fluttering about the Northwest.

Reports have been coming in from Yosemite, Seattle, British Columbia, Mt. Adams, Crater Lake, Suttle Lake, South Sister, Mt. Hood, Mt. Jefferson, Green Ridge. Tortoiseshells are everywhere. If you were at Suttle Lake recently you would have seen thousands of them "mudding" for minerals along the shoreline.

My wife Sue and I took a drive to The Big City of Bend last Thursday; between our home at Sun Mountain and Bend we counted more than 25 tortoiseshells fluttering by, some, unfortunately, bouncing off the car and leaving yellow, fatty smears on the windshield.

When this phenomenon took place in 1987 special equipment was installed near Redding, California to wash butterfly remains from windshields and radiators of trucks going up and down I-5.

This is not really a "migration" but more of a "dispersal" of butterflies. It apparently began in California last spring and has been building all summer. Mother Nature's objective is survival of the species, in this case achieved by dramatic reproduction that provides millions of butterflies the opportunity to exploit new territory.

Female tortoiseshells are looking for Snowbrush Ceanothus (Ceanothus velutinu) to lay their eggs on, that's the caterpillar's food plants. Should that fail before cold weather, then some will find a safe place to spend the winter, which is probably why you see them fluttering in and out of your barn, garage, outbuilding, under vehicles, foundations and other dark hidy-holes.

This incredible hatch of butterflies is like no other in their lifecycle; they are loaded with fat in order to have enough fuel to explore everywhere around them for snowbrush and survive winter. They stop in dark places at night to keep out of the cold, then in the morning flutter to the first patch of sunlight to warm up their muscles, and off they go again exploring.

Ravens, jays, robins, yellow jackets - just about every predator that knows what a tortoiseshell butterfly tastes like is after them - all that fat in the butterfly's body is rich in protein. This is another process of Natural Selection working at its finest.

Those tortoiseshells that have the right genes or find themselves in a safe place when the cold returns will be able to winter over as adults. The butterfly's "blood" (if we can call it that in human terms) contains antifreeze. Even at 31 below zero, wintering butterflies in this area can make it. But not Monarchs, they are a tropical species and must fly south for the winter.

If you want to take the time, it would be valuable information if you would count the tortoiseshells you have seen, tally up the numbers, dates and locations and send the data along to my wife, Sue and me at [email protected] It will contribute toward better understanding of what goes on in the wonderful world of butterflies.