[author]Story & photo Mary Gardner[/author]
‘Could it be a Drummer, a Grinder or a Screamer?’ I wondered, flicking through the identification pages. ‘Maybe it’s a Green Grocer, or a Twanger or a Tree Creaker? Whichever, it is certainly a Cicada.’
The insect rests on its shell. It is already larger than that casing from which it emerged. The veins in the wings are still pink. Soon they will be black. The two large eyes seem unaware of me. The three small eyes in the centre of the head – on what do they focus?
The delightful common names of Australian cicadas largely come from the knowledge of children only a generation or two ago. A specialist called Max Moulds counts 700 different cicada in collections throughout the country and finds only about 200 are identified by taxonomists. Along with other specialists here and in New Zealand, he finds these childhood monikers useful as this great work of identification progresses.
Moulds, like others, finds the songs of cicadas are unique to each species. Identification pages online include sound bites. Males produce the sounds by flexing their tymbals. These are a set of delicate ribs found at the end of the thorax (second section) near the beginning of the abdomen (third section). The abdomen acts as a resonating chamber. Both sexes have sound receptors called tympana, a flat section under the abdomen.
Some species of males sing solo. Others collect in a location and sing as a chorus. When a female and male approach each other, both gesture to each other with unique patterns of clapping or flicking their wings.
When the female is ready to lay her eggs, she ‘taste tests’ the upper branches of a tree. Only certain species of trees will do. Cicadas are true bugs, whose only nourishment is sips they take directly from the veins of a tree branch. They rarely cause much damage. In fact, they are often bossed around by ants who worry them away from their drinking holes. The ants then collect the sap. Henri Fabre, the famous French entomologist, observed this and declared that Aesop’s tale of ‘The Ant and the Cicada’ was plain slander.
Having found the right tree, the female lays eggs which hatch into grubs. These do the original bungy jump, with no aids. Hitting the ground, they dig a chamber right alongside a tree root. The sap at the roots in the xylem tubes is exactly what their mother wanted for them. This is their only nutrition as they grow underground.
Australia’s cicada grubs live underground for any number of years, depending again on the species. Only the North American ones have the predictable 13- or 17-year cycles. Of all 38 groups of cicadas, 35 are unique to Australia. With origins going back 245 million years, they have sung for dinosaurs.
How does a group of creatures only 50mm in size continue as a chorus over aeons? What happens to them in this century when, globally, we use an average of 2.9 kilograms of pesticide per hectare of farmland? Can we rediscover what we as children loved about them?