Shivering butterflies look like you might imagine from your own experiences in cold weather. The butterflies shiver their wings rapidly in an attempt to warm the muscles inside.

The monarch's flight threshold is about 55°F (13°C). Flight threshold means that this is the lowest temperature at which monarchs can fly.

In order to fly well, with lots of control, they need to attain thoracic temperatures in the upper 20s or even 30s—pretty close to the temperatures that warm blooded mammals run. Monarchs can manage to get themselves airborne and glide—and occasionally flap with some control—at temperatures much lower than that, but they cannot fly well at temperatures in the teens.

You'll often hear people say the butterflies are trying to get warm enough to fly. But it may be that shivering helps them get warm enough even to crawl off the ground when they are too cold to fly. Monarchs can crawl at temperatures as low as 41°F (5°C).

Shivering is most common when the temperatures are low. But it's possible to even see a monarch shivering during the peak warmth of the day. When butterflies are down on the ground to drink water they would be cooled by the cold water and need to shiver to raise their body temperature for movement.

Try This! Shivering Simulation
Find a volunteer who's willing to shiver. Ask him to sit on the edge of his chair and shiver all the muscles in his body at once-- arms, legs, feet, and hands. How many seconds does it take until he can feel his body warming? How long until he can feel himself getting tired? How long until he begins to perspire?

• National Science Education Standards

Copyright Journey North (journeynorth.org). All Rights Reserved.