THERE'S a weird, unseasonal silence around Orange at the moment with one of summer's most recognisable sounds conspicuous by its rarity.
Missing is the piercing high-pitched hum of thousands of male cicadas sending out their relentless call in the hope of snaring a mate in their six-week adult life.
Department of Primary Industries collections curator, entomologist Peter Gillespie said normally, November and the leadup to Christmas through the New Year was the time our ears were heavily assaulted by the common green grocer, the most common of the town-dwellers.
"This year has been a really poor year for them," he said.
"You've actually got to think backwards. Some years they come out in big numbers and some years they don't. Generally they've got about a two-year life cycle."
Two year's ago, Orange was battling drought and the aftermath of bushfire on Mount Canobolas meaning the environment was not supportive of cicada population growth.
"Ones we have here are generally two to three years - you will get them coming out every year but some are, if you like, a low year. I've seen possibly half a dozen.
"The thing is, they've got to get a certain number of them out to start doing the chirruping, that's temperature dependent so you need the hot days and we haven't had so much of those up until recently.
"Once they get to that certain temperature, they all start chirruping at once, and they're all males and they're all competing for females and that whole chorus thing is asexual thing. If there's not enough numbers for them it's like going to an empty bar, a pickup bar."
Mr Gillespie explained females lay their eggs in the bark of trees before the larvae hatch and head down the trunk and into the soil. There they attach themselves to a healthy tree root, living in the ground for between two or three years.
"They're in total dark, in soil attached to the main roots and they're just sucking juice," he said explaining it's that relationship with the tree that controls growth and to a certain extent, lets them know when it's time come up.
"If there's not much juice moving around it's either winter or its the middle of a drought so they are, if you like, figuring out what the biology of the plant is doing above the soil."
While this year numbers are down, last year Orange was flooded by the cyclochila australasiae, of which the western European tree-loving green grocer is the most popular in town. Mr Gillespie said there are over 100 species of cicada, with yellow Monday, masked devil and the blue moon close relatives.
"They are most successful reproducers in big years, they contract the females in, there's lots of activity, they're all doing their stuff, having said that the birds are taking out a proportion of them the entire time."
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