The last couple of weeks have seen the emergence of cicadas from their ground-dwelling nymph phase, en masse. Our forests are now humming with waves of cicada song, which in some species like the GreenGrocer, the Double Drummer and the Yellow Monday, can reach a deafening 120 decibels! The fence posts along the trail to Yagon Beach, in Myall Lakes National Park, were covered in nymphs a few weeks ago, where the adults were unfurling their wings and making their presence heard far and wide.
It got me thinking about these distinctive insects, and their biology.
We have over 200 species of Cicada in Australia, which are grouped in the Order Hemiptera on account of their sucking mouthparts. The common names are quite wonderful, and include monikers such as the Black Prince, the Floury Baker, and Red Eye, to name but a few. Apparently, some of these names have been coined by children, who often take a keen interest in these fascinating critters which are easy to spot, catch and plonk in a jar for a few hours of amusement.
Here a cicada, possibly a Floury Baker, hardens its wings after emerging from its carapace.
Cicadas spend most of their lives underground in the nymph stage of their development. The adults only live for a few weeks after emerging from the nymph form, during which time the males sing to attract a mate. The singing is often unified into a pulsating chorus, and songs are species specific so as to attract the attention of the right type of female. This choral singing by cicadas is thought to be a defense mechanism to ward off predators by confusing them with sound, particularly birds. Who’d have thought the insect world came up with such an effective surround-sound system long before the home theatre setups were developed in the labs at Sony!
After mating, the female deposits her eggs into the stem of a plant with a specialised injection organ, called an ovipositor. The eggs hatch and the flightless nymphs fall to the ground, where they use their specialised digging appendages to burrow into the ground. Here they will stay for many years (up to 14 in some species), feeding on the root sap of plants, such as Eucalypts and grasses.
When fully grown and if the environmental conditions are right, the nymphs dig their way out of the ground and find a trunk, or other vertical post, to latch onto whilst their carapace splits and the adult cicada emerges. The newly hatched adult cicadas are very soft with wings folded in a complicated origami pattern which must unfurl and harden up before they can fly off and join the local dating scene.
These mass cicada gatherings provide easy pickings for many of our local birds, but also for bats, including the Vulnerable Grey-Headed Flying Fox. They are also predated upon by other insects that parasitise the body with their young, for example, some species of wasp, spider, ant, mantid and tree crickets.
A true sign that summer is here, the incessant daily cicada song may well drive you mad over the weeks leading up to Christmas and beyond, but I encourage you to go out and take a close look at these fascinating creatures. They truly are a sight to behold.
For more information on Australian Cicadas, go to the Australian Museum website; or this excellent publication:
- Moulds, M.S. 1990. Australian Cicadas. New South Wales University Press. 217 pp., 24 pls.
Image credits Isabelle Strachan
Article by Isabelle Strachan
