Field Notes from Mexico
by Dr. Bill Calvert

February 17, 2005


"What had been a drab display of cryptic camouflage was now color and movement."

"Our lesson was plain and simple: butterfly activity—and butterfly motion—was powered by the sun."
Day 1: The Herrada Colony
On Sunday, February 13th a group of teachers from Georgia, Minnesota, and Texas, and myself traveled from Mexico City to the butterfly colony “Herrada."
(See map.) Although they didn’t know what to expect, I was full of anxiety. The day was cloudy and the mountain obscured by haze. Just as I had worried, there were no butterflies, neither streaming down the road nor in the arroyo where there is water for them to drink.

This was the first part of what was to become a dramatic lesson that illustrated the power of the sun to affect butterfly behavior.

Day 2: The Rosario Colony
The following day we ascended to the Rosario Colony and trudged up the 781 feet to parking lot to the colony. Again the day was cloudy and cool. The dormant, clustered butterflies presented themselves as a Japanese tapestry, showing no color. Moans of disappointment were audible from the onlookers.

Day 3: The Chincua Colony
We visited Chinua the following day and found an intermediate situation. The morning had begun crystal clear but rapidly clouded over. We trekked the 2 kilometers to the colony on horseback arriving early afternoon. The sky was mainly cloudy, but had breaks among the clouds, allowing the ambient [temperature] to heat up a bit. Butterflies were flying about, but not in great numbers.

Then the sun burst through for a 15-minute period and the scene changed dramatically. Millions more butterflies opened their wings, and millions took to the air. What had been a drab display of cryptic camouflage the day before at Rosario was now color and movement. The clouds came back and millions of baskers took to the air.

Day 4: The Pelon Colony
The next day was Wednesday. We ascended 2,500 feet to the Pelon colony again by horseback (the poor horses) to find a cloudless sky and butterflies flying everywhere. They were on all the flowers, and they basked on vegetation as far as a mile from the colony. The clusters that had been closed and inactive at Rosario were now full of color and action. The spectacle was simply dazzling. We descended the mountain exhausted but much elated. (The horses breathed a sign of relief.)

Our lesson was plain and simple: butterfly activity, and butterfly motion, was powered by the sun.

Map of the monarch colonies in Mexico.
(Click map to enlarge.)