New Zealand Cicadas
The most common species of cicada in New Zealand* is the Chorus Cicada (Amphipsalta zelandica) seen above. These cicadas and their disused exoskeletons are often found on the trunks of trees at this time of the year and we start to hear their chorus in parks and bush.
When I first moved to New Zealand in 2004 I was a bit ignorant of New Zealand insects. Early in my Kiwi pest control career a gentleman called and said he had found these ‘weird insect skeletons’ stuck to his tree trunks and could I identify them. I asked him to bring some to the office and when he did I excitedly looked at them and didn’t know what they were, but they looked weird to me too.
I took them to my office to do some research, while my Kiwi colleagues were giggling in the background, I suspect. I quickly identified them as the discarded exoskeletons of Chorus Cicada.
As if that was not bad enough, about the same time I picked up my new company vehicle and was driving through Hagley Park when I pulled over because I thought there was a stone, or some such, stuck in the brakes of the vehicle, for that is what the sound sounded like. When I stopped, and the sound continued the penny dropped.
In my defence, there are not many cicadas in my native Ireland!
The experience made me read up a bit more about cicadas and their fascinating life-cycles.
Females deposit rice-like eggs in groves she makes with her ovipositor in the bark of trees. The groves can be damaging to small tree limbs.
Small pale termite-like cicada hatch from the eggs and feed on the tree sap. Then they drop to the soil below and dig down to the tree roots where they feed on the roots of plants. Depending on the species the cicada may stay underground, feeding on roots, for 2-17 years. The Chorus Cicada has a nymphal stage which lasts 25-44 months). Then they emerge from the ground as nymphs and climb a tree where they shed their exoskeleton and emerge as a winged adult.
The adult cicadas seek a mate and the cycle begins again. The males compete to make the loudest and best sound to attract a mate. Male cicadas use ribbed membranes (tymbals) on each side of the base of the abdomen to produce sound. Each tymbal is attached to a powerful muscle. As the muscle contracts, it buckles the tymbal, much as when the domed lid of a jar is first unsealed, causing a pulse of sound. Then the tymbal pops back into shape. This is rapidly repeated to cause the distinctive cicada call.
This is the sound of summer.
Types of Cicada Life Cycle
Annual: Cicadas emerge every year.
Proto-periodical: Cicada species with proto-periodical life cycles might emerge every year, but every so many years they ‘co-ordinate’ and emerge in large numbers.
Periodical: Emerge together after long periods of time, e.g. Magicicada septendecim will emerge every 17 years. The number of years between emergence tends to be a prime number, which may be to avoid emerging at the same time as their predators.
*You will find information on the New Zealand cicada species on the Landcare Research website.