At this time of year our eardrums are overwhelmed by the rasping, buzzing chorus of cicadas. It goes on and on and on and on. Unending. It comes from the bushes, the tree trunks, the branches. Seemingly everywhere. You can't escape it.

It is a sound synonymous with summer, with hot, muggy days. And while the sound may get on the nerves of city dwellers, for trout anglers it is a sweet melody because they know that if they stalk the banks of the Tongariro River where it slows and spreads before losing itself in the blue depths of Lake Taupo they will see the long, yellow-brown shape of a brown trout lying by the grass.

And they know that if they approach slowly and stealthily, lifting and placing each foot as if watching out for landmines, and strip line from the slender fly rod and cast to exactly the perfect spot so that neither the line nor the transparent monofilament leader lands near the fish but the big, spiky dry fly alights gently and drifts on the oily surface, curling until it edges into the trout's cone of vision, then the thick shape might stir, the eyes swivelling upwards to follow the fly.

The broad pectoral fins will fan out and, just like a plane gliding through the air, it will rise up slowly until its nose breaks the silver surface and the mouth will open and suck in the fly. And if they wait, with heart pounding, for a second until they feel the line go taut, and lift the rod, the game will be on.

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They also know that if they drive over the hill to Lake Otamangakau - where the windswept waters are punctuated by sharp explosions as the trout smash cicadas blown on to the water - the trout may fall for their feathered offering and the game will be on there too.

The trout living in the streams, which wind through meadows or tumble through rocky gorges in the bush, will also be looking for cicadas struggling in the surface film.

For this is a time when the trout lose their suspicion of foreign bodies floating through their domain and strike savagely at anything that might be a large, struggling insect.

It is the time of the cicadas.

To other cicadas their song is a joyful one. After spending 17 years trapped below ground in the dark earth, you would be singing when you saw the sun, too.

There are more than 20 different types of cicadas in this country and they're usually green or brown or black; but they all have the same lifestyle - females lay eggs in the bark of a tree and the tiny hatchlings or nymphs drop to the ground where they burrow and feed by sucking sap from the roots, growing into a fat, white grub. Then, after anything up to 17 years, they seek a partner and crawl out of the ground and up the nearest tree or post - anything. This happens on long, hot summer days and is triggered by the combination of heat and moisture. In the sun, a strange thing happens. The insect inside swells and bursts the skin, crawling out as the cicada we know so well, complete with transparent wings with see-through veins. Its whole purpose in life now is to find a mate and repeat the cycle, and it is the male cicada that makes the distinctive strident call - legs rubbing on the body - to attract a partner. It must work pretty well because there are a lot of cicadas all going for it.

So when you hear the cicadas calling, spare a thought for the love-sick bloke clinging to a branch hoping to lure a lady into his lair. And spare a thought for the fly fisherman who dusts off his box of cicada imitations and heads into the hills, full of hope that the cicadas are singing along the riverbank just as they are in the city.