From September to November each year, the Bogong moths make their springtime mass migratory flight from the Darling Downs in Queensland, northern Australia, south to the Bogong Plains in Victoria. Right in their flight path is the Snowy Mountains and Canberra, the capital of Australia.
Bogong moths (Agrotis infusa), large and brown with a wingspan of 4 centimeters (1.5 inches), fly at night and rest during the day. They feed on the nectar of plants, especially grevilleas, and deliberately eat a lot in preparation for their long flight, just like runners load up with carbohydrates before a marathon. They add up to 60% of their body weight before they travel south-east. The flight is 3,000 kilometres (1,864 miles) and many of them perish before they reach their destination.
They start their lives in Queensland as eggs in the soil. Caterpillars (called cutworms) emerge from the eggs and feed on plants and vegetables, such as cabbages, peas, and cauliflowers, growing up to 5 centimeters (2 inches) long. They pupate (change) into cocoons that are situated under leaves and the litter of plants for about a month before they emerge as moths. They fly south from September to November to escape the summer heat of tropical Queensland. From November to February, the summer months, they rest in the cool caves in the Victorian Alps. There they stay until autumn when the fly back to Queensland in March to mate and lay their eggs. After they lay their eggs, they die. The moths have a lifespan of one year.
During their migration, tens of millions of them cause quite a disturbance in cities as they cling to buildings, fly into air-conditioning ducts, and cover the ground and floors in people’s homes, looking like a brown carpet. There have been known to be about 17,000 moths per square metre and look like roof tiles.
MARTINA NICOLLS is an international
aid and development consultant, and the author of:- The Shortness of
Life: A Mongolian Lament (2015), Liberia’s Deadest Ends (2012), Bardot’s Comet
(2011), Kashmir on a Knife-Edge (2010) and The Sudan Curse (2009).
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