Typically the season for Bogong moths as they migrate through NSW to the Australian Alps, this time of year usually sees a smattering of the creatures.

“Periodically, some species of moths will mature at the same rate and then for several days there will be an unusual amount of them,” said Dr Paul Weston, entomologist with Charles Sturt University’s Graham Centre.

“Mostly it’s [because] a critical temperature that has been reached along with higher rainfall.”

The end of November brought higher than usual temperatures, and a total monthly precipitation register of 101.6mm, which is 57mm above the expected. 

“Moths tend to synchronise [maturation] at the end of summer, so it is a little unusual if we’re seeing large amounts this early,” said Dr Weston.

Primarily seen at night gathering around lighting fixtures, moths may have a varying lifespan of between a few weeks to a few months.

But Dr Weston expects Wagga’s sudden increase will be short as they migrate further south.

He is also encouraged to hear the insects have congregated inside the cities and have so far avoided the more the Riverina’s rural environments.

“Moths generally only attack plants, so if they’re staying away from the country parts I suppose there’s less chance of them destroying crops.”

As the first month of summer draws on the lookout has also begun for locusts, which typically begin forming their egg enclaves at this time of year.

“It’s been a few years since we’ve had any major locust activity. But it does depend on those egg masses deep in the soil.

“When it’s dry, they’ll stay dormant but if we have a lot of rain at the end of summer, enough to penetrate deep into the soil, then they’ll start to hatch.”

Despite an alert for El Nino in the Riverina, the rest of summer is expected to deliver an average monthly rainfall rate of 40mm to 45mm.

It may not prove enough to disturb the locusts, but if surrounding regions see higher totals there may still be movement.

“Locusts can travel hundreds of kilometres, so they can still show up suddenly overnight if hot, dry wind currents are favourable to them,” said Dr Weston.

“But typically, hot and dry weather is hard on insects, so if it lacks that moisture, we’ll see fewer insects.”