Sandflies in New Zealand: where they are and how to cope

New Zealand has no snakes, no dangerous spiders worth worrying about and nothing that will bother you at night. What it does have is the sandfly, and it makes up for all of them. If you are heading to the West Coast or Fiordland, this is the one thing worth preparing for.

We rent campers here and live in Auckland, and sandflies are comfortably the most common complaint we hear back from guests — always from the same handful of places, and almost always from people who were told they were not that bad.

What are sandflies, actually?

They are small black flies, around two to three millimetres, of the genus Austrosimulium. Only the females bite, and they do it because they need a blood meal to produce eggs. They carry no disease of any kind, which is genuinely worth knowing: a sandfly bite in New Zealand is uncomfortable, not dangerous.

The bite itself you often do not feel. The reaction comes hours later — a hard, intensely itchy lump that can last three to five days, and longer if you scratch it. Some people barely react; others swell up. There is no way to know which you are until it happens.

Where sandflies are worst

This matters more than anything else, because they are not evenly spread. Much of New Zealand has almost none.

• West Coast of the South Island — the worst, from Karamea down through Punakaiki and the glaciers
• Fiordland — Milford Sound, Doubtful Sound, Te Anau's lake edge
• Catlins and parts of the Southland coast
• Abel Tasman and Golden Bay — present but milder
• Most of the North Island, Canterbury and Central Otago — barely an issue

There is a Māori account of this. Hine-nui-te-pō released the sandfly at Milford so that people would not simply stand there admiring the fjord forever and forget to do anything else. Having stood there being bitten, it is a hard story to argue with.

What actually works

Plenty of things are recommended online. These are the ones that hold up.

• Repellent with DEET or picaridin — apply before you get out of the vehicle, not after
• Long sleeves and long trousers at dawn and dusk, when they are most active
• Standing in wind — they are weak fliers and a breeze clears them
• Covering your ankles, which is where most people get bitten
• Antihistamine cream for afterwards, and not scratching, which is easier said than done

What does not work: citronella bands, most natural sprays, and hoping. They are also not deterred by the cold — a still, overcast day on the West Coast is prime sandfly weather.

Keeping them out of the camper

This is where campervan travel has an advantage over a tent, provided you use it. Every window in our campers has a fly screen, and the whole game is closing them before dusk rather than after you have already let a dozen in.

The practical routine that works: park up, close the screens, then open the door. If you cook outside, do it before dusk or after dark rather than during it. And if you have let a few in, they collect on the inside of the windows in the morning where they are easy to deal with.

One more thing about the West Coast in particular: it is worth having the repellent in the door pocket rather than in a bag in the back, because you will want it in the ten seconds between stopping and getting out.

Should this change your route?

No. The places with the worst sandflies are also some of the best places in the country — Milford Sound, the glaciers, the Catlins coast. Skipping them to avoid an insect would be a poor trade.

What it should change is your packing. Repellent goes in before the second pair of shoes. Our campervan packing list covers the rest, and the West Coast camping guide covers where you will actually meet them.

How long do sandfly bites last?

Longer than a mosquito bite, and that is the part nobody warns you about.

The bite itself is barely noticeable. The reaction arrives hours later, and can itch for several days — sometimes a week or more if you scratch it. People react very differently: one of you can be covered while the other is barely touched.

The practical advice is the boring advice. Do not scratch, use an antihistamine cream, and keep bites clean, because broken skin in a damp climate gets infected.

What time of day are sandflies worst?

Dawn and dusk, overwhelmingly. They are also worse in still, damp, overcast conditions and near water — which describes most of the West Coast most of the time.

Two things follow from that. Wind is your friend: an exposed, breezy site is far more comfortable than a sheltered one beside a stream. And the hour you most want to sit outside with a drink is the hour they are most active, which is why repellent goes on before you stop rather than after.

Are sandflies dangerous?

No. They are not known to transmit disease in New Zealand, unlike sandflies in some other countries. They are a comfort problem rather than a health one.

According to Māori tradition, the goddess Hine-nui-te-pō released the sandfly at Milford Sound to stop people being so overcome by its beauty that they never left. Having stood there being bitten, the story feels well observed.