How to Survive Milford Sound Sandflies
- Alice Neilson - Fiordland Enthusiast & Writer
- 5 days ago
- 5 min read
If you're planning a trip to Milford Sound, you've probably heard about the sandflies. The pesky little insects are one of the most common things visitors ask us about, but the good news is that with a bit of preparation, sandflies are manageable, and they won’t stop you from enjoying your day in Fiordland National Park.
Key Takeaways
New Zealand sandflies don't carry diseases that affect humans, so while bites are annoying, they're not dangerous
Strong insect repellent with high DEET concentration (like Bushman or Aeroguard Tropical Strength) is the most effective
Sandflies are most active at dawn and dusk, and on warm, cloudy, humid days, while bright sunny days and heavy rain reduce their activity
Wearing light-coloured clothing and covering exposed skin reduces your chances of being bitten
You won't encounter sandflies on the boat during your Milford Sound cruise, as they don't venture out over open water
The Legend of Te Namu
Sandfly bites can be an annoying part of a trip to Milford Sound, but according to Māori legend, the sandflies in Milford Sound are doing exactly what they were created to do.
When the goddess of death, Hine-nui-te-pō, looked upon the extraordinary beauty of Piopiotahi (Milford Sound), she worried that the area was so stunning, people would want to stay forever and eventually destroy its beauty.
So she released Te Namu (sandflies) at what we now call Sandfly Point. The name "namu" translates roughly to "little devils.” Their purpose was to make the area just annoying enough that visitors wouldn't overstay their welcome.
It's a clever explanation for why one of the most beautiful places on Earth also happens to be home to one of the most irritating insects.
Understanding New Zealand Sandflies
New Zealand sandflies belong to the family Simuliidae, which is the same family called "blackflies" in most other countries.
Only two species bite humans here: the New Zealand blackfly and the West Coast blackfly. Both are tiny, measuring just 2-3 millimetres, and look identical to the naked eye.
Like mosquitoes, only the females bite, as they need blood to produce eggs. They're not particularly fussy about their sources either, happily feeding on mammals and birds, with a particular fondness for penguins.
Why Their Bites Feel Worse
International visitors often find New Zealand sandfly bites more intense than insect bites they've experienced elsewhere. The bites feel worse because, unlike mosquitoes that pierce the skin like a needle, sandflies use knife-shaped mouthparts to slash the skin and then lap up the resulting pool of blood.
This cutting action creates a larger wound than a mosquito bite. The sandfly also releases saliva containing histamines and anti-clotting agents into the wound, which triggers your body's immune response. The result is more swelling and more intense itching than you might be used to from other insect bites.
The Good News About Disease
Unlike some sandfly species found overseas, New Zealand sandflies don't transmit diseases to humans. Our sandflies can transmit avian malaria to birds, but nothing that affects people.
The only health risk comes from scratching bites until they break the skin, which can lead to secondary bacterial infection. The bite itself won't make you sick, but your fingernails might if you can't resist scratching.
Your Sandfly Survival Guide
Prevention
Use a Strong Insect Repellent
If you ask a Milford Sound local about natural insect repellents, they'll likely tell you not to bother. Sandflies require a serious repellent to deter them, so look for products with high DEET concentration.
Bushman Heavy Duty and Aeroguard Tropical Strength are commonly recommended. Both are available at most New Zealand pharmacies, and Aeroguard is often stocked in supermarkets too.
Cover up with Light Colours
Sandflies have poor eyesight and rely mainly on scent to find you, but they can see dark shapes more easily, so wearing light-coloured clothing makes you harder to spot.
You can wear long sleeves and long pants to reduce the amount of exposed skin, then apply repellent to your hands, neck, and ankles.
Take an Antihistamine
If you’re worried about itching, it can be helpful to take an antihistamine tablet at the start of your day as a preventative measure. It won't stop sandflies from biting or stop bites from itching entirely, but it can reduce your body's histamine response, making the bites less intense.
If Camping, Burn Insect Coils
While classic citronella candles provide some protection, insect repeller incense coils tend to work better. They contain citronella and sandalwood, but the smoke from the burning coil creates an additional barrier that masks human scent more effectively than candles alone. You can find the coils at hardware stores.
Treatment
Don't Squash Them While
They're Biting
That might sound counterintuitive, but squashing a sandfly mid-bite can make things worse. It causes them to tear at your skin more, creating a larger wound and potentially depositing more saliva. More saliva and a bigger wound mean a larger histamine response and more itching.
Apply Stingose Gel or Spray
Stingose contains aluminium sulphate hydrate, which soothes itching and reduces swelling. It's particularly effective for people who have intense reactions to bites. Available at most pharmacies in either gel or spray form.
Keep Antiseptic Cream Handy
If you're prone to scratching bites without realising (especially in your sleep), applying antiseptic cream helps prevent secondary infection.
Where You Will (and Won't) Find Sandflies
High-Risk Areas
Sandflies breed in free-flowing water like streams and rivers, so you'll encounter them near any running water and in humid bush areas. Most of the Milford Road travels through forested areas with streams, so sandflies are present at many scenic stops.
Low-Risk Areas
Sandflies generally stay within about 10 metres of running water, so you won't encounter them in Te Anau or Queenstown town centres, as you're too far from their breeding habitat. They also don't venture out over open water like lakes or ponds.
Weather-Based Activity Patterns
Sandflies are most active at dawn and dusk, and on warm, cloudy, humid days. Bright, hot sunny days with low humidity see fewer sandflies. Heavy rain also keeps them at bay. The worst conditions are that middle ground of overcast and humid, which is perfect sandfly weather.
The Best News: No Sandflies on the Cruise
Once you're on the boat for your Milford Sound cruise, you can relax. Sandflies don't fly out across the water, so you won't be bothered during the cruise itself. The terminal area at Milford Sound may have some sandflies around, but once you're out on the fiord, you're in a sandfly-free zone.
While you can’t stop the sandflies from biting, with the right preparation, they don’t need to be a major issue during your Milford Sound visit. Using a strong repellent, wearing light-coloured clothing, and carrying something to treat bites will make a noticeable difference.
Managing the sandflies is a small price of admission to one of the most beautiful places in New Zealand. As a visitor spending a day exploring Milford Sound, you're doing exactly what goddess Hine-nui-te-pō intended: enjoying the scenery, then heading home before the sandflies force you to leave.
Frequently Asked Questions
Will sandflies bite me through my clothing?
Sandflies can’t bite through fabric, so covered skin is protected skin. This is why long sleeves and long pants are recommended, even in summer.
Focus your insect repellent on exposed areas like hands, ankles, neck, and face. Lightweight, breathable fabrics in light colours give you the best combination of protection and comfort in Fiordland's often humid conditions.
How long do sandfly bites take to heal?
Reactions vary between people, but sandfly bites typically remain itchy for several days. Keeping bites clean and resisting scratching helps them heal faster.
Are sandflies worse at certain times of year?
Sandflies are present year-round in Fiordland, but they're most active during the warmer months from late spring through autumn (October to April). Within any given day, they're most active at dawn and dusk and during warm, humid, overcast conditions. Bright sunny days, cold weather, and heavy rain all reduce sandfly activity.