Sounds of a Kiwi summer
The whirring and buzzing song of the cicada is a familiar soundtrack to many New Zealanders in the heat of summer - but just what do we really know about this rowdy insect?
We have around 40 species of cicada in New Zealand, and probably the most familiar to us is the clapping cicada, which is actually two very closely related species that form the basis of our summer soundtrack in much of the country.
Cicadas have an unusual way of making a racket. Unlike weta, which produce sound through stridulation (rubbing their legs along their abdomen - kind of like the washboard in a hillbilly band), the cicada makes its noise through a tymbal. This instrument is a membrane located on the side of the cicada's abdomen, which when the cicada flexes or vibrates, "pops" in and out. The abdomen underneath is largely hollow, so the sound which resonates. Think along the lines of what happens when you grab an empty plastic coke bottle and squeeze (but really, really fast - cicadas can do this up to 600 times a second!). As many of you will know, cicadas are LOUD. Some species of cicada can reach a volume of 120 decibels - about as loud as an ambulance siren - and enough to cause hearing damage if one was next to your ear. Only the male cicadas "sing" (though the females do produce a toned-down mating call apparently), resulting in this 2000-year-old Greek saying "Happy are cicadas' lives, for they have voiceless wives."
Both the adult and nymph cicadas have a piercing mouth part to suck fluid or sap from plants. (Photo: DOC)
Cicadas spend much of their lives underground as larvae - up to five years for some of our species. One species of cicada in the United States stays in the ground for 17 years. When they emerge, they find each other (that song comes in handy), mate, and the female lays eggs in grassy plants. The nymphs find their way to the ground and burrow down when they hatch, using their straw-like mouth parts to suck the sap of plant roots for the next few years before the whole thing starts again. The cast off "shell" or skin of cicada nymphs can often be found where the nymph has emerged, the shell has split along the thorax and abdomen, and an often brightly coloured cicada adult has stepped out.
New Zealand cicadas remain much of a mystery (though this cicada page is a great place to start!). We have the only alpine cicada in the world, and cicadas that camouflage themselves according to whether they're residing in tussocks, forests or rocks. It appears that to early Maori, the chit-chat of English settlers was also mysterious, leading them to dub the new arrivals' language as "te reo kihikihi" or cicada language, because of its harsh sounds, compared to what they believed was the more melodious Maori language.
Have you heard the dull roar of cicadas in your neck of the woods this summer? Do you consider it to be a part of your summer soundtrack? Found any cicada nymph cases? I'd love to hear from you.