To test for this, the scientists strapped butterflies into a flight simulator, allowing them to point in any direction while flying “on the spot”.
They surrounded the chamber with a magnetic coil system and varied the inclination angle of the field – effectively changing the position of the equator and the poles.
The monarchs responded by turning in the direction they perceived as south.
Crucially – the magnetic compass only worked when the butterflies were also exposed to light in the ultraviolet-A/blue range. This was not present in previous magnetic experiments with monarchs – explaining why they failed to find evidence of such a compass, the researchers believe.
“To our knowledge, this is the first demonstration of the use of an inclination magnetic compass by a long-distance migratory insect,” said Prof Reppert.
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, or even use Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for MakeCode, CircuitPython, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.