Reina Hill is playing the reluctant host to some unexpected visitors in her Batemans Bay home.

Since Friday, her house has been swarmed by bogong moths. 

"I walked out my door and was hit in the face by thousands of them," she said. 

"I swear there was millions of them layered on various areas under my deck, under my eaves and all around the windows."

Ms Hill was not alone in noticing the sudden influx of the endangered insects. 

About 800 moth sightings have been logged on the citizen science platform iNaturalist since Friday, with more than 200 logged in the past 24 hours.

Every year, the peanut-sized moths migrate to the NSW Alps to escape the summer heat before returning to their inland breeding grounds in autumn.

But the insect's population has fallen steadily since the 1980s due to drought and warming temperatures.

In 2017, numbers crashed by as much as 99.5 per cent, and in 2021 they were listed as endangered.

'Just trying to migrate'

Western Sydney University Entomologist Eleanor Drinkwater told 702 ABC Sydney it was pleasing to see the moths in such significant numbers.

"The last few years we haven't seen so many bogong moths," she said.

Dr Drinkwater said the moths were on their way to the high country around Mount Kosciuszko as the weather warmed up. 

"They're not trying to get into your house, they're just trying to migrate," she said. 

"For some of these little individuals that people might see, they're going to be travelling hundreds, if not thousands, of kilometres."  

Bogong Watch Project manager at Invertebrates Australia Linnea Emneby said many people had forgotten what a migration looks like. 

"We have seen a decline in bogong moths this decade, which has changed people's perception of what a migration looks like," she said. 

"It's just incredibly encouraging to see them actually bouncing back." 

According to Ms Emneby, there were several theories that might explain the phenomenon. 

One is that increased rainfall in northern parts of the state has produced an abundance of food for larvae. 

Another theory is that warmer weather has caused the flowers that attract the moths to bloom earlier than normal, luring them south. 

But Ms Emneby said the small creatures had likely used recent north-westerly winds to travel to the alps. 

"Bogong moths are known to kind of hitch a ride on winds," she said.

"They're very small creatures and they travel vast distances.

"If there is wind going the way of the migration, they'll fly at that level in the same way you descend or ascend in a hot air balloon."

Increase in numbers the 'norm'

University of Sydney biologist Dieter Hochuli said the moths would be found hiding in crevices in the day to avoid predation by birds.

"There's a lot of birds and mammals and everything that's going to want to eat them.," Mr Hochuli told 702 ABC Sydney. 

"So, basically, they're just finding a good spot to spend the day."

The moths are a food source for many birds and pygmy possums.

Mr Hochuli said while the moth was listed as endangered by the International Union for Conservation of Nature (IUCN), they were not listed as endangered in NSW or federally. 

"The reason there are concerns is that they have these massive population fluctuations and cycles," Mr Hochuli said.

"They're a complicated animal for an endangered animal because there could be billions of them.

"Those of us that are old enough to remember the Sydney Olympics or the opening of Parliament House will remember we had similar kinds of events, just massive numbers."

Dr Drinkwater encouraged capturing and releasing the moths if they were stuck inside, or turning outside lights on and turning indoor lights off to draw them out of homes.

She also called for submissions of photos to iNaturalist and the Moth Tracker website to help researchers understand their migration.

“This is a brilliant opportunity for us to learn more about what they're doing," Dr Drinkwater said.