This student story was published as part of the 2025 NASW Perlman Virtual Mentoring Program organized by the NASW Education Committee, providing science journalism experience for undergraduate and graduate students.
Story by Jada Summerville
Mentored and edited by Stephanie M. McPherson
Bogong moths journey over 1,000 kilometers across Australian terrain using the stars as one of their guides.
A recent study published in Nature by a lab at Lund University in Sweden has shown that Bogong moths utilize both the stars and Earth’s geomagnetic field during their long-distance migrations. Further electrophysiological analysis identified a never-before-recorded neural foundation for this behavior.
This work gains us further understanding of how certain visual cues can be encoded into an insect’s brain, leading to a distinct behavior that allows these insects to carry out such a demanding task. “It’s astonishing what moths can achieve with such tiny brains … able to travel such great distances using only the Earth’s geomagnetic field and the stars,” says Andrea Adden of The Francis Crick Institute, who co-authored this study.
Understanding how these moths and other insects navigate is essential when studying the effects of climate change on migration patterns. It is even more essential for the Bogong moth, an endangered species. The loss of these moths could disrupt the Australian food chain, especially for the endangered Mountain pygmy possum, which relies on these moths as a food source.
Fitting the Milky Way into a tiny brain
In the spring, Bogong moths migrate to caves in the Australian Alps to hibernate over the summer. In the autumn, they then migrate north to their original breeding grounds and reproduce. The cycle repeats the following spring.
To investigate how these moths accomplish such a journey, the authors captured moths just before embarking on these migrations. After tethering them in a flight simulator, the authors measured their orientation under different night sky conditions. In both clear and cloudy nights, the moths were able to orient themselves in their proper migratory directions. This strongly suggested that Bogong moths take directional cues from Earth’s geomagnetic field.
The authors wondered if these insects also took guidance from any visual cues, such as the stars. To test this, they again tethered moths in a flight simulator and removed the sensation of a magnetic field. Using a projector mimicking the night sky, they found that the moths flew in their appropriate migratory directions in response to a natural starry night. When given a randomized nightscape, the moths were completely disoriented, flying off in every direction. These experiments showed that the stars alone were sufficient for these moths to navigate.
Thus, moths have two compasses, and both are essential. Just as the night sky can become obscured, Earth’s magnetic field can be disrupted by solar winds or geomagnetic storms. Yet following the stars may have a bit of an advantage over Earth’s magnetic field. “There is more accuracy in using the stars to reach a specific destination than the geomagnetic field,” says Adden.
Encoding the stars
To understand how observing the stars results in this migratory behavior, the authors had to study the moths on a deeper level — their brain.
The authors again used a night-sky flight simulator and pinned the moths down to record their brain activity. They found that specific neurons in the moth’s vision, navigation, and steering centers all responded to specific orientations of the night sky.
“The most surprising thing, was they [the authors] found a different type of neuron for processing the stars that was not found to process celestial cues in other insects,” says Basil el Jundi who studies the sky compass of monarch butterflies at the Norwegian University of Science and Technology and who was not involved in the study. The moths’ neuronal responses are unique compared to other sky-navigating insects like the dung beetle and monarch butterfly. These findings mark the discovery of a novel neural circuit, one that is used to encode the Milky Way in the tiny brain of the Bogong moth.
Questions linger about these small creatures and their odysseys across Australia, such as how these moths are able to discern the time of day to appropriately match it to the position of the stars. Additionally, how the Earth’s magnetic field is encoded in many insects’ brains remains a mystery to the field.
Jada Summerville
Stephanie McPherson
The NASW Perlman Virtual Mentoring program is named for longtime science writer and past NASW President David Perlman. Dave, who died in 2020 at the age of 101 only three years after his retirement from the San Francisco Chronicle, was a mentor to countless members of the science writing community and always made time for kind and supportive words, especially for early career writers.
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