Sandflies

As I sit here writing this, there are several dozen small red welts covering my arms and legs. These are insect bites courtesy of Austrosimulium australense, one of the species of New Zealand sandfly. It is all I can do to refrain from scratching the hell out of each and every one of them. But I know that will just make it worse.

The story as I understand it is that the female of this species who lives along streams in the bush needs or prefers a ‘blood meal’ to obtain nutrients in order to produce eggs. This is where I apparently came in.

Sure, there are no snakes, dangerous spiders or scorpions here in New Zealand. There are no predators like mountain lions or bears as in Colorado. But lest you think that everything is perfect in the pastoral heaven which is New Zealand, there is at least one real pest, termed a nuisance by the Ministry of Health here, and that is this beast to which I refer—the sandfly.

Close-up of the enemy

Close-up of the enemy (1)

Sandflies, called namu by the Maori here and often called blackflies in other parts of the world, are tiny. No, these aren’t like the common housefly or the giant horse flies back in the US. Sandflies are only 2-3 mm in length. You have to look closely to even see them landing on you. When you swat them, they produce a smear of blood—your blood.

There are 19 species in New Zealand and only three of those species bite humans, and it is only the females that do the biting. Males are apparently vegetarians. Sandflies are found throughout the country wherever there is flowing water and bush (forest) and often on beaches.

Our good friend, Captain Cook, having no doubt seen and encountered numerous adversaries on his journeys took time to comment on the New Zealand sandfly in his journal.

The most mischievous animal here is the small black sandfly which are exceeding numerous … wherever they light they cause a swelling and such intolerable itching that it is not possible to refrain from scratching and at last ends in ulcers like the small Pox.’                – Cook 1773

Yes, I couldn’t agree more! These bites have got to be amongst the most itchiest things I’ve had in my life.

Somewhat later, Captain John Lort Stokes of the Acheron in 1851 while surveying nearby Doubtful Sound on the South Island was equally plagued by the insects and resisted his initial temptation to name certain areas Venon Point, Sandfly Bay and Bloodsuckers Sound.

Sandflies breed in streams laying their eggs on rocks, after which larvae hatch and then pupate before emerging from the water’s surface days later as full-fledged flies.

Biting_sandfly

Sandfly biting finger

Sandflies are in the biological subfamily Phlebotominae—that’s right like the word phlebotomy which refers to removing blood from the body. Sandflies inject chemicals that inhibit blood clotting and then suck up the blood. They also stimulate the local release of histamine.

Visitors and newcomers to NZ who haven’t been exposed seem to react the most. Locals describe them as being “sweet.” Apparently I am sweet. Sandflies prefer to attack ankles, feet, wrists, hands, the neck and face—pretty much everything that’s commonly exposed.

Some hardly feel the bite, for others it is more painful. And supposedly some people become less sensitive over time. Hopefully I will be one of those people.

People vary in their reaction to the bites. Characteristically the bites cause intense itching, redness and swelling. The itching can go on for days. For some, the symptoms can apparently last for months.

Multiple sandfly bites with prominent reaction

Multiple sandfly bites with prominent reaction

How do sandflies hone in on their victim? Factors may include exhaled carbon dioxide (your breath) and also odors but at closer distances important factors are the shape of the host contrasted with the background and infrared radiation—heat.

What did they feed on before the millions of tourists who descend on New Zealand each summer? Birds, seals, bats and penguins.

How bad are they? They can be very bad. People quantify, measure, these type things. A high biting rate is 1000 bites per hour. One researcher in 1977 collected 360 sandflies biting his exposed arms and legs at one time, giving what is called an equivalent biting rate of about 4000 per hour. To my mind, that’s no longer being bit, that’s being eaten.

So what can you do? Cover up. Wear long sleeve shirts and pants. Lighter colors are better. Blue and black are the most attractive to sandflies. Keep standing or walking. Sandflies tend to stay down low. Close your car windows when you stop to avoid them joining you on your trip. The biting frenzy is most prominent in the early morning and at dusk and on cloudy, overcast days. Do what you can to avoid those times. Sandflies are slow moving; if you keep walking, they can’t keep up. Wind also is a blessing.

And then there’s insect repellent. Oh, there are a number of natural repellents but it seems DEET works quite well. They make a 100% concentrated formula, as opposed to the normal 30%, which some people recommend.

Once bit, you can spread antihistamine cream or calamine lotion on the bites to provide some relief. Sometimes the bites get infected if you scratch the heck out of them and will require antibiotics.

Any good news? Well, the sandflies here don’t spread any terrible diseases like Leishmaniosis which their compadres transmit in other parts of the world.

New Zealand is a bit hush-hush about the sandflies. Oh, they mention them in the guide books and in the official publications. But the truth is that few of the millions who visit the west coast of the South Island and particularly Fiordland and Milford Sound escape unscathed. And apparently in some areas at certain times, they can make a vacation truly miserable.

Giant sandfly sculpture, Pukekura, New Zealand

Giant sandfly sculpture, Pukekura, New Zealand

As for me, for now I will just have to live with my bites.

 

1) www.teara.govt.nz/files/a-15352-lcr.jpg

References include: https://www.landcareresearch.co.nz/__data/assets/pdf_file/0003/43149/FNZ68_Simuliidae_2012_screen.pdf

 

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5 thoughts on “Sandflies

  1. Ok, let me get this straight …these little darlings are attracted to dark colors, particularly black….and the native’s color of choice is…black !! Am I missing something ??? Good thing N Z is such a visual Paridise or it would just be…sunammis, boiling springs, volcanoes, earthquakes, killer caves, and….sand flies !!! Love the posts …keep me’ coming !

  2. Ok, I’m bringing my Orange Bronco shirts but not my blue ones. Paul, do you know if permethrin
    is an effective repellent for these little critters?

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