The bogong moth (Agrotis infusa) is a temperate species of night-flying moth, notable for its biannual long-distance seasonal migrations towards and from the Australian Alps, similar to the diurnal monarch butterfly. During the autumn and winter it is found in southern Queensland, western New South Wales, western Victoria, Tasmania and also in South and Western Australia. It is an icon of Australian wildlife due to its historical role as an important food source and because Aboriginal peoples would come to where the moths spend the summer to feast on them and hold intertribal gatherings.
Starting around 1980 and accelerating rapidly after 2016, the bogong moth population has sharply declined as a result of increasingly severe droughts, along with increased temperatures in caves used by the moths for aestivation, both primarily resulting from anthropogenic climate change. In December 2021 the bogong moth was added to the IUCN Red List as an Endangered Species. Its presence has contributed to the naming of numerous locations and landmarks. For example, a town, Bogong, in the Australian state of Victoria has been named after the moth. Mount Bogong, located south of the Bogong High Plains, is also named after the moth, with its traditional name, Warkwoolowler, meaning the mountain where Aboriginal people collected the "boo.gong fly".
In the Australian state of New South Wales, a series of mountains in the Kosciuszko National Park are named the Bogong Peaks.
Description
thumb|Side profile of an adult
Adult bogong moths have an overall dark brown colouration, with a dark stripe interrupted by two light-coloured spots on the wings, distinguishing it from other moths.
Bogong moth eggs are dome–shaped in appearance and are vertically ridged. They are 0.7 mm (0.03 in) in diameter and 0.4 mm (0.02 in) in height. A study published in 2018 concluded that the bogong moth uses a combination of the Earth's magnetic field and recognisable landmarks to calibrate their route. In 2025, researchers found that neurons in these insects responded to a starry sky, and suggested bogong moths use both magnetic fields and stars to orient themselves and navigate.
However, there are also nonmigratory populations; this generally occurs in areas with favourable conditions, where migration to avoid harsh conditions such as seasonal changes in larval food crop abundance is not necessary. The parasites are transmitted to bogong moths through water; the early instar larval nematodes reside in the debris of the cave floors of common aestivation sites, and crawl up to reach the moths through trickles of water coming down the walls. Aggregations of bogong moths in aestivation sites has led to the bioaccumulation of the pollutant in both the surrounding local environment and within predators, particularly in the endangered mountain pygmy possum.
In 2001, a few months after rainfall had washed out debris consisting of dead moths from within the cave, the complete death of local grasses was seen outside of an aestivation site of the bogong moth. Investigation into the causes of the grass mortality showed that the concentration of arsenic in the surrounding areas was much higher than normal, and the source was determined to be the bogong moths. Since the bogong moths do not feed at their aestivation sites, they had absorbed arsenic from lowland feeding sites as larvae and subsequently transported it over long distances into the mountains. Bioaccumulation, the absorption and accumulation of substances by organisms, occurs with arsenic in bogong moths.
Other biologists and ecologists have pointed to the dramatic effect on animals which feed on the moths, which are an important source of protein for wildlife, including the threatened mountain pygmy possum as well as other insectivorous mammals and birds. "The vulnerability of the Australian Alps to climate change is the worst in the world because we've got these short little mountains so when it gets warmer, there is nowhere for these cold-adapted species to go", according to Euan Ritchie, a wildlife ecologist at Deakin University.
Pest of crop plants
Bogong moths have had a role in damaging crop plants since winter pastures serve as breeding grounds and larval food sources.
Migration issues
Millions of bogong moths have been blown off course from their spring migration into major cities like Canberra, Melbourne, and Sydney due to strong winds, with notable instances of bogong moth invasions including the 2000 Olympics in Sydney. based on a February 2021 assessment.