SOUTH LAKE TAHOE, Calif. - If you thought you were seeing many more butterflies around Lake Tahoe than normal, you would be correct. The entire Lake Tahoe Basin is in the midst of a massive outbreak of the winged beauties, especially in the Angora Fire burn area and along the east shore.

What most people are seeing is the California Tortoiseshell Butterfly, orange and black on the top of the wings, shades of black underneath. They thrive on the Mountain Whitethorn, part of the Ceanothus family, something that itself is thriving where the Angora fire burned in 2007.

"It is pretty phenomenal," said Tahoe Institute of Natural Science (TINS) Executive Director Will Richardson, Ph.D. "It's exceptional. I have not seen a flight quite like this before."

Richardson said it is possible there are currently millions of the California Tortoiseshell population in Lake Tahoe, and all the ones being seen now were produced here.

"This year is a big local flight," Richardson said. It's the biggest he said he's seen in the twenty years he has lived in Lake Tahoe.

Five to six weeks ago there was a large flush of butterflies from lower elevations. That group laid their eggs in Lake Tahoe, and what people are now seeing around Lake Tahoe is that new group of butterflies.

A big winter and warm summer created healthy leaves on the whitethorn, something caterpillars thrive on and the local shrubs and trees continue to provide for the butterfly.

Some of the butterflies winter in Lake Tahoe, finding a tree's bark or corner of a building to wait out the season, though many will head for lower elevation during the winter. Some of that westward flight may start soon.

The California Tortoiseshell don't migrate but they do move north and south, east and west.

TINS conducted a butterfly count one week ago and they didn't see any of them flying yet, just found them in the cocoon stage.

"We are having quite the eruption," said Richardson.

When driving in the Tahoe Mountain Road area, or wherever other outbreaks are, use caution when driving. They don't know the danger of cars and will fly right into them.