A masterclass in punching above its weight, this tiny insect measures only two to three millimetres and is almost invisible until it lands. Unlike a mosquito, which uses a hypodermic needle approach, the sandfly is a butcher. The female, the only one that bites, uses saw-like mouthparts to literally hack a hole in your skin. She then spits into the wound to prevent the blood from clotting and laps up the pool. That spit is what causes the legendary, soul-crushing itch that can last for weeks, a parting gift that reminds you of your holiday long after you have left the beach. They are biologically visual hunters. They do not just sniff you out. They look for movement and dark, heat-absorbing surfaces. This is why your black rubber jandals are essentially a neon sign saying eat here. Because they are clumsy fliers, they hate the wind and the rain, which is why they vanish the moment a breeze kicks up, only to reappear the second the air goes still. They are the ultimate fair-weather nightmare. They do not hunt at night, that is the mosquito's shift, preferring the full light of day to carry out their relentless, coordinated assaults on your lower extremities. The lifecycle of the namu is tied to the purity of our water. The larvae live in fast-flowing streams, clinging to rocks with tiny hooks and filtering organic matter from the current. They are actually a sign of a very healthy waterway. If you are being eaten alive, at least you know the river is clean. Once they emerge as adults, the males head off to drink nectar like civilised insects, while the females head straight for the nearest mammal to gather the protein needed to develop their eggs. In the absence of humans, they feed on seals, penguins, and even the occasional sleeping sea lion. The sandfly dance, that frantic waving of arms and slapping of legs, is a national pastime. No repellent is fully effective against a determined Fiordland swarm. They will find the one millimetre of skin you missed between your sock and your trouser leg. They are the tiny, winged tax-collectors of the New Zealand bush, ensuring that every visitor pays a blood price for the view. They are the reason we own deet by the gallon and the reason why, in the middle of a stunning mountain sunset, you will still hear the rhythmic thwack-thwack of someone trying to save their ankles in a pair of jandals.