14 DAY TRIAL // Every year, hoards of hundreds of millions of monarch butterflies migrate from Canada to Mexico, across the continental US, in a 4,000-mile journey led entirely by the Sun. Scientists have wondered for a long time how come the small insects can navigate sophisticatedly enough to follow the path of the star non-stop, while always keeping their bearings southwards. A new study has revealed that the butterflies have GPS devices of sorts in their antennas, which allow them to keep the time of the day.
This is crucial because the Sun is not fixed at the same location in the sky throughout the day. The monarch butterflies have to know the time of the day they are in, then calculate the Sun's position relative to that, and only afterwards set a flying course. They are able to do these complex actions with an amazing accuracy, experts say, and get precisely to their destination each year, regardless of the weather or other factors. They land in groves of fir trees no larger than the base of the Great Pyramid of Giza, Nature News reports.
Finding out that these “clocks” resided in the antennas came as a shock to the international scientific community, as previous studies suggested that they might be located inside the insects' brains, alongside other navigation circuitry. “This is a novel function for the antennae, and a huge surprise overall. It brings us closer to understanding how time and space are integrated on [the monarchs'] remarkable migration,” University of Massachusetts Medical School expert Steven Reppert explains. He is the lead author of a new paper detailing the finds, which appears in the latest issue of the journal Nature.
“We just assumed both [components] were in the brain. There have been a ton of studies now suggesting the Sun compass is there,” the expert adds. In his experiments, the researcher tested to see if monarch butterflies would keep their southwards direction if they had no antennas. Once deprived of them, the insects kept flying in a constant direction, but that direction was random, in that several specimens flew in separate directions. This evidently shows that antennas are of tremendous importance for their ability to orient themselves by the Sun.