The youngest presenter at a national conference on insects in Whanganui this week was Olly Hills - aged 11.

And he's written a book about New Zealand cicadas - the snoring, the braying, the chirping, the variable, the bronze and many others.

One of the organisers of the Entomological Society conference, Rudi Schnitzler, discovered Olly when he found a cicada and used his book to identify it. He invited the young Hamilton naturalist to present at the conference.

Olly had a 25-minute slot on April 11, and Mum Tara Hills said he listened raptly to the other speakers as well.

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"Most of them were interested in the same things that I am. I know a bit about most insects in New Zealand, but normally I stay with cicadas," he said.

Olly got interested in cicadas because of their noise. He climbed trees, captured them and started writing a book because he thought one was needed. His family has travelled from Mt Cook to Pirongia to search out new species.

He'd really like to go back to the South Island.

"It has different types of black cicadas. They're really hard to identify and tell apart," he said.

There are at least 42 species of cicada in New Zealand. The adults emerge in early summer to mate, lay eggs and die. It's the males that make that summer cicada sound, to lure femalesfor mating.

Females lay eggs on trees, and the scars they make in the process can cause small branches to drop off. The eggs look like grains of rice, and drop to the ground where the cicada nymphs burrow in.

They spend two to 17 years underground.

"They dig themselves a little chamber around a tree root and suck the sap out of [it]."

The noises cicadas make vary. The loudest species in the world is the Australian double drummer.

In New Zealand the April green makes such a high pitched noise that only children can hear it. Others snore, chirp, clap, click or bray.

People are starting to talk about using insects as food, and Olly has seen articles about eating cicadas.

"Let's just say I don't really agree," he said.

For more on cicadas, go to Cicada Central

For more on Olly Hills, go to The Spinoff