Monarch Chrysalis Light Orientation

Monarch chrysalises tend to pupate with their gold crown facing away from the light inside a room.

A few years ago we noticed this odd behavior in our lab. When we opened our rearing containers, most of the pre-pupa (J’ing caterpillars) were hanging with their legs toward the light.

Eventually we decided to do an experiment. We set up several rearing totes, marking the lids to indicate which tote was to be placed where in the lab. Not only the specific rack, but which shelf and which position on the shelf. Not only which rack, but racks had to be in a position that received equal light from the lights in the room.

The totes that were marked were always placed between two totes and always placed directly under another shelf. Another tote was never placed on top of the test tote. Test totes were placed on both sides of the lab. We were testing for light direction as well as north/south/east/west orientation influences.

As we had noticed, almost all caterpillars positioned themselves with their legs facing toward the light in their pre-pupa stage. One pupated, the gold crown was facing away from the light.

What a great science experiment for students! Students could set up different rearing containers, different light situations, use indoor and outdoor light, natural and artificial light, and raised dozens of Monarch butterflies to compare chrysalis orientation. We would be interested in adding their science experiment results to this page.