Wave of butterflies lights up weather radar A painted lady butterfly flies near daisies in a garden in downtown Denver Wednesday, Oct. 4, 2017. (AP Photo/David Zalubowski)
Wave of butterflies lights up weather radar

A lacy, cloud-like pattern drifted across a Denver-area radar screen. It turned out to be a wave of butterflies. It was 70 miles wide. That's according to forecasters.

Paul Schlatter works for the National Weather Service. He said he first thought flocks of birds were making the pattern he saw on the radar Tuesday. But the cloud was headed northwest with the wind. Migrating birds would be southbound in October.

He asked birdwatchers on social media what it might be. By Wednesday he had his answer. People reported seeing a loosely spaced net of painted lady butterflies. They were drifting with the wind across the area.

Schlatter said the colors on the radar image are a result of the butterflies' shape and direction. The colors he saw were not their own colors.

Midwestern radar stations sometimes pick up butterflies. But Schlatter believes it's a first for Denver.

An unusually large number of painted ladies are sometimes mistaken for monarch butterflies. They have descended on Colorado's Front Range in recent weeks. They feed on flowers. They sometimes fly together in what seem like clouds.

Sarah Garrett is a lepidopterist at the Butterfly Pavilion. It is in Westminster, Colorado. She said people from as far away as the Dakotas have called to report seeing the butterflies. Their population typically surges with plentiful flowers.

Research on the painted ladies in North America is limited. Scientists believe they migrate to the southwestern United States and northwestern Mexico. This happens in the fall. 

In Europe, studies using radio tracking have shown they migrate south from Europe to Africa in the fall. They return in the spring. Studies also show that monarch butterflies often use wind to their advantage. They glide on currents for periods of time, Garrett said.

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Why doesn’t radar show color of butterflies?
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  • ReesePratt-del
    10/12/2017 - 05:54 p.m.

    The Radar does not show the color of the butterflies because radars do not show color.

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