Residents from the Blue Mountains to Sydney’s inner west have reported unusually large numbers of bogong moths in recent weeks, with the insects gathering in any opening and staying longer than usual.

Each summer the bogong moth travels about 1,000 kilometres from breeding grounds in southern Queensland, northern NSW and western Victoria to cool mountain caves where it hibernates. This massive migration is a natural part of its life cycle.

Caitlyn Forster, a lecturer in entomology at the University of Sydney, explains that the moths use the stars to navigate. Bright artificial lights in urban areas can distract them, pulling the insects toward streets and houses.

Strong winds can also knock the moths off their intended route. Dr Forster notes that gusts may blow them toward the coast and into residential areas, where they become easy to spot.

Marissa Parrott, senior conservation biologist at Zoos Victoria, says that recent increases in rain and abundant food in NSW and the ACT have attracted larger numbers of moths. She describes the current surge as the best year for the species in almost a decade.

To understand where the moths are going, researchers from Western Sydney University and Invertebrates Australia are painting a small blue dot on some moths in the Blue Mountains and attaching tiny paper tags to thousands more from Mount Kosciuszko. Citizen scientists are asked to report sightings, helping map the insects’ distribution and flyways.