Migrating Painted Lady Butterflies Spotted On The National Weather Service’s Radar Imagery

Scientists at the National Weather Service have been wondering about the orange radar blob that they have seen on the radar imagery over Denver. They thought it was a flock of birds, yet it turned out it was a swarm of migrating painted lady butterflies.

The forecasters said that it is not unusual for flying insects such as butterflies to be identified by radar. Paul Schlatter, the NWS meteorologist who first spotted the radar blip, said they had not seen a signature like this in a while. He told CBS News that they detect migrating birds all the time, but they fly north to south.

He asked the help of the public through a message on Twitter asking for identification of the bird species. Most answered it was a swarm of butterflies. It is about a 70-mile wide (110 km) mass flight of painted lady butterflies.

Schlatter said that the butterflies are everywhere, and the signatures of butterflies that they mostly see are monarchs around Denver. On the other hand, they have not seen this type of butterfly before. They were all excited about it.

Schlatter added that insects hardly ever produce such a coherent radar signature. He further said that the bright colors on the radar suggest the shape and direction of the insects. The dark purple is when the butterflies are flying toward or away from the radar beam, according to Schlatter.

Meanwhile, Sarah Garrett, a lepidopterist at the Butterfly Pavilion in Westminster, Colorado, said that they are not 100 percent sure of what type of butterflies they are. On the other hand, she said that there has been an abundance of the painted lady butterflies in Colorado.

She added that they started seeing the butterflies in Colorado in March this year. This is almost two months ahead of the schedule. Garret explained that these butterflies migrated to the northeastern U.S. for reproduction to occur earlier and the population grew substantially in the summer.

A painted lady butterfly rests on a purple coneflower.
[Image by Pat Wellenbach/AP Images]

Meanwhile, painted ladies are also referred to as the Cynthia group of colorful butterflies, which are known all throughout the world. The butterfly’s upper side is orange-brown with darker wing bases. Its underside has a black, brown, and gray pattern with four small submarginal eyespots. It has a wingspan of 5.1 to 7.3 cm, according to Butterflies and Moths of North America.

Painted ladies fly fast and far, up to 100 miles per day during their migration. They could reach a speed of about 30 miles per hour. And they fly low when migrating at about six to 12 feet above the ground.

[Featured Image by Sloot/Thinkstock]