The monarch butterfly resting on a fennel. Image: Wikimedia creative commons licence.

Every autumn, monarch butterflies across Canada and the USA migrate over 2,000 miles to the relative warmth of central Mexico.

This journey is repeated instinctively by generations of monarchs, despite a fall in population numbers due to the decline in milkweed, their primary food source.

In a paper published in the journal Cell Reports, researchers from the universities of Washington, Michigan and Massachusetts are believed to have cracked the secret of the internal, genetically encoded compass that the monarchs use to determine their direction of flight.

The monarch butterfly is a long-distance migrator. Just like birds, it migrates both north and south. Image: Luna sin Estrellas, Flickr. Creative commons licence.

Washington University Professor Eli Shlizerman worked with biologist colleagues to record directly from neurons in the butterflies’ antennae and eyes.

He said they have identified the input cues that allow the butterflies to fly in the correct southeasterly direction.

We identified that the input cues depend entirely on the Sun, one is the horizontal position of the Sun and the other is keeping the time of day.

This gives [the butterflies] an internal Sun compass for travelling southerly throughout the day.

The research team then used that data to create a circuit model to simulate these neural control mechanisms.

In a Washington University statement, Professor Shlizerman said:

We created a model that incorporated this information- how the antennae and eyes send this information to the brain.

Our goal was to model what type of control mechanism would be at work within the brain, and then asked whether our model could guarantee sustained navigation in the southwest direction.

The scientists model shows that butterfly migration can be understood and simulated as a cellular circuit.

It even accounts for how the butterflies get back on track if they veer off course.

Two monarchs enjoy some afternoon nectar. Image embedded from Getty Images. 

The monarch butterfly is a threatened species.

The three lowest populations on record have been recorded in the last 10 years.

It is hoped this breakthrough may be able to help save the species from further decline, by helping scientists to understand how they navigate and locate their food.

Prof Shlizerman told the BBC said that one of his team’s goals was to build a robotic monarch butterfly.

It’s a very interesting application that could follow the butterflies and even help maintain them.

Their numbers are decreasing, so we want to keep this insect – the only one that migrates these huge distances – with us for many years.

A robotic butterfly may be able to follow the insects and track their entire migration.

It seems this wonderful insect may have a future as bright as its wings.

All images sourced from Wikimedia creative commons and are in the public domain. 

Music: Come Fly With Me, written by Jimmy Van Heusen, lyrics by Sammy Cahn, performed by Frank Sinatra. 1957. Duration: 3.19