Sunday, 7 December 2014

Just Like Clockwork

Each year in mid September, on a cold spring night, the Northern Green Grocer Cicada, Cyclochila virens, begins its curious serenade.

The co-ordinated cacophony begins after dark around 6.40 pm. The area pulsates with the calls of the males of the species for about 13 minutes each night. Then quiet.

This odd behaviour continues but it starts a few seconds later night after night. As at the 23rd of November, it started at 6.54 pm. Adding to the peculiarity of this symphony is that it seems geographically co-ordinated. Whether on the Atherton Tableland, the slopes of Mt Lewis, or here in Kuranda, the cicadas start calling at the same time each night. I am uncertain if it is the same individual cicadas that are singing over the course of the species' activity. This seems unlikely.

The Northern Green Grocer is a large cicada. An average male measures about 70mm in length from head to the tip of the wings. They seem to inhabit rainforest trees well off the ground.

When handled an individual will buzz and vibrate. But that does not seem to affect the behaviour of certain predatory birds. Distressed cicadas can often be seen in the grasp of Black Butcherbirds and Spangled Drongos.

I will attempt to monitor these cicadas and determine the finale of their symphony.


randomtruth said...

Fascinating. My brain almost melted trying to figure it out, but then I remembered your days down there are getting longer right now. Sounds like these guys have some pretty accurate light meters. Would be interesting to graph their daily start time against Astronomical Twilight. Bet they'd track perfectly.

Linda Rogan said...

Hi David,
We have had very little cicada activity near our home near Greensborough Vic. so far this season. I have been watching for them particularly for David Emery's project.

I'm looking forward to a brief trip to Kuranda in February. Hoping for a different suite of insects from what we normally see on August September visits.

Thanks for help you have given with some ID of insects I have placed on BowerBird. Linda Rogan Editor Victorian Entomologist

Mr. Smiley said...

Thanks Ken and Linda for your comments.

The drought seems to have broken but it is rather hot for this part of the country.