Back to this week's update.

Basking Butterflies in Missouri
You can tell it's a cool morning. The monarchs are all holding their wings at the same angle, catching the rays of the sun. "The overnight low was 47°F," noted Tom Nagel, who took this picture early Wednesday morning. These monarchs must warm their muscles before they can continue their travels.

Monarch Butterflies at roost site in Mexico.

Photo: Tom Nagel