The ear-splitting creatures have arrived three to four weeks early after rain and a warm winter, they suspect.

Hunter residents have reported an abundance of the ‘‘red-eye’’ variety.

Sydney University Professor David Emery said cicadas were in large numbers from the Blue Mountains to the Queensland border.

‘‘They started pouring out of the ground after rain,’’ Professor Emery, a cicada enthusiast, said.

‘‘There’s a plague of red-eyes.’’

He said several species of ‘‘big cicadas’’ had made appearances along the NSW coast.

These include green grocers (variations are yellow Mondays, masked devils and blue moons) double drummers, black princes, red-eyes, razor grinders and cherry roses.

‘‘They’ve all come out three to four weeks early this year,’’ he said.

‘‘It’s been an exceptional season.

‘‘It’s probably because of a warm winter, but we don’t really know.’’

The high-pitched, piercing song of the cicada is a soundtrack of summer.

Australian Museum entomologist Dave Britton said only males made the loud song, probably for survival reasons.

The song warned off predators and attracted females, Dr Britton said.

‘‘It literally deafens birds, their main predator,’’ he said.

‘‘It makes it hard for predators to locate individual cicadas when they’re calling together in one big noise.’’

Big cicadas take about four to six years to transform from egg to adult, after which most live for only a few weeks.

Females laid eggs on branches and when the ‘‘flea-size nymphs’’ hatch, they burrow underground. 

‘‘They pop out when the conditions are right,’’ Dr Britton said.

Professor Emery has been tracking cicadas for 23 years.

He enjoyed watching the ‘‘metamorphosis’’ – the process of them emerging from a shell, which takes about two hours.

‘‘I’ve had a fascination since childhood,’’ he said.

‘‘I love them because they’re part of summer.’’

Professor Emery said Australia had the ‘‘greatest cicada diversity of any continent’’.

‘‘There are more than 700 species and only about half have names,’’ he said.

‘‘New species are being found all the time.’’

The brown-coloured double drummers – which grew to about 12 centimetres – were the largest.

‘‘There was a huge emergence of them at Hawks Nest a few years ago,’’ he said.

Cicada facts:

■ Only male cicadas sing

■ They sing to find a mate and repel predators

■ Different species have different songs

■ Adult cicadas live only a few weeks

■ Most of their lives (four to six years) are spent as nymphs underground

■ Cicadas feed only on plant sap using their piercing, sucking mouths

■ Cicadas feed on a huge range of plants, including eucalypts and grasses

■ Birds, bats, spiders, wasps, ants, mantids and tree crickets prey on cicadas.

Source: Australian Museum