This season more cicadas have chosen to venture above ground after years living beneath the earth, Department of Primary Industries (DPI) scientific collections curator Peter Gillespie said.

“It’s quite seasonal ... it often depends on the preceding seasons,” he said.

“The last couple of summers have had above average moisture and they’ve responded this summer by emerging.”

Mr Gillespie said the species of cicada that populates Orange, thrives on non-native plants particularly enjoying softwood trees and the many European trees around town.

“When they’re immature, underground, they suck the juices from the roots of the trees and when they’re adults they suck the juice from the branches,” he said.

“They only do relatively minor damage and they play an important role for the local bird ecology.”

Cicadas spend two to three years underground before they emerge and are usually lucky to last a month before they are snapped up by a bird.

Although experts are still uncertain what makes cicadas emerge in great numbers when they do, Mr Gillespie said it had social benefits for the insects when trying to attract a mate.

“The noise you hear is for the boys to attract the girls,” he said.

“They get into synchronicity and align all their calls and sing in tune.”

Mr Gillespie said in bushland around Orange there are different varieties of cicadas with specific calls.

“When the guys all chime in together and build up to speed it can be deafening,” he said.