It is cold at the monach over-wintering sites in Mexico! It's sometimes so cold that the butterflies become paralyzed. They are unable to move their muscles. Why don?t the butterflies "lose their grip" and fall from the trees when they're paralyzed?
"Monarchs have incredible claws,? says Dr. Bill Calvert. ?They are amazingly well adapted to hang on. Even though the butterflies are dormant, the claws hook on and the butterflies remain in the trees.
"But I have seen them fall. When they are too cold to open their wings, they float down--but with their claws extended--so they can grab something on the way down. You?ll see them catch on people?s heads, backs, clothing--everywhere.
These well-developed claws found are on their fore walking feet. In extremely cold weather there are descriptions of butterflies falling like bullets because they can?t even open their wings.?
Dr. Brower added, ?Often clusters of butterflies hang together with their claws interlocked. When one lets lose you may get a whole string of them coming down.?
National Science Education Standards