George Novak Science & Environment Sandflies New Zealand’s most popular destinations are plagued by hordes of tiny marauders, hungry for blood. Like the vampires of bad television they tear holes in our skin and sup upon the blood which wells up. Yet, as in The Art of War, the secret of survival may be as simple as understanding the enemy.



Written by Claudia Babirat Photographed by George Novak

I used to tell people that New Zealand doesn’t have any dangerous animals, that they’re free to roam to their heart’s content. But after hearing the horror stories, counselling attack victims and being bitten myself, I now suggest they arm themselves with the most powerful insect repellent they can find.

The good folk of the South Island’s West Coast have a way of distinguishing a tourist from a local, even from a great distance. A local, they will tell you, is a “brusher”, while visitors are “slappers”. It’s not a description of the latter’s late-night conduct at the pub but their involuntary behaviour in response to meeting another type of local, the sandfly.

If you’ve never encountered a sandfly, you could be forgiven for not being overly impressed. It is, after all, just a minuscule insect. Six tiny legs. A pinprick of a body. Stumpy little wings. The only audible sound the little beast manages to generate is an indignant, high-pitched whirr—and that only happens when it gets hopelessly tangled in your hair. Yes, as far as first impressions go, the pint-sized critter could come across as a bit of an entomological runt.

Until it bites.

The pain is short, sharp and surprising. Short, that is, because our instinct is to extinguish it as rapidly as possible. Even as your head rotates in the direction of the target, the urge for vengeance has kicked in. Before reason has time to catch up, SLAP, the open palm of your hand comes down with a force many times greater than what is actually required to dispatch the little tyke.

The moment of triumph is short-lived, however. In fact, it lasts precisely as long as it takes to look up and realise that the splattered stain on your forearm has brought backup. Like errant electrons, hundreds of the critters are now—quite noiselessly—orbiting your air space, locking in on suitable landing pads, and touching down. Hands, ankles, eyelids, ears—no exposed dermal area is spared. In defence, you bat at the moving cloud in the immediate vicinity of your face. First with one hand, as if in loose rebuke to an insult, then more fervently with two. You try to yank down the legs of your three-quarter trousers. Realise with horror that your socks don’t go up past your ankles.

Take an illusive step backwards. Bat some more. Smack your cheek. Stomp. Twist. Swipe. Strike, whack, SLAP!

From a distance, I’m assured, this syncopated dance is rather fun to watch.

Which is why, when I arrived in the West Coast fishing community of Jackson Bay one overcast Saturday morning in early June, the locals greeted with me with big smiles.

I smiled too—though perhaps somewhat maniacally—because I was here to be bitten. Not in the name of science, nor as part of some masochistic ritual, but because of a dare.

It began with a visit to Australia. Here I fell victim to countless things that bite and sting, whereupon my unaffected partner Peter suggested I have “weak genes”. Filled with indignation, I rose to his challenge: a five-minute tête-à-tête with New Zealand’s most notorious sandfly species, baring all. So here we were, Queen’s Birthday weekend, hiking into the West Coast wilderness just north of Fiordland—one of the most sandfly-prone areas in the country—and not a drop of DEET in sight.

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To get a sense of how bad sandflies are in some areas of the lush West Coast, you need only surf the internet. Page upon page is devoted to personal stories of holiday horror, of tourists being forced to flee, claiming they were sucked dry by insects “hungrier than dehydrated vampires” and “big enough to rape turkeys”. Landmarks bear names such as Mosquito Hill and Sandfly Point, and had Captain John Lort Stokes of HMS Acheron not shown restraint as he was surveying places such as Doubtful (aka “Bloodsucker”) Sound in 1851, there would have been many more.

Even Maori, who had a much longer period in which to get used to the varmints, were overwhelmed by the ferocity of Fiordland’s sandflies and promptly incorporated the beasts into their rich mythology. They claimed that when Hine-nui-te-po (the goddess of the underworld) saw the fiords, she deemed them too beautiful to be modified by man. As a deterrent, she released a liberal dose of sandflies. Her ploy worked. Most Maori restricted their visits to the area to occasional hunting, fishing and greenstone-gathering trips. Even today, the human population density of Fiordland remains virtually zero. Unless you’re prepared to row at least 300 m offshore, or climb to an elevation of 1500 m—the sandfly’s uppermost limit—there’s simply no escaping the thirsty little devils.

The most sobering sandfly statistic, however, is hidden in a scientific article penned by a New Zealand entomologist—and a particularly dedicated one at that. While collecting the diminutive insects at Jackson Bay (the very locality I was now at), he was bitten a whopping 300 times in five minutes. That equates to one sandfly bite per second.

If I was going to survive my own imminent sandfly encounter, I clearly needed to find out more about my enemy.

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It turns out that unlike sandflies, people who devote their life to studying the little biters are a rare breed. My search eventually led me to Professor Douglas Craig, a retired Kiwi ex-pat living in Canada who, by a stroke of luck, had recently been recruited by Landcare Research to sort out New Zealand’s sandfly taxonomy. Craig was quick to grasp the reason for my correspondence. “I’d love to be there when you get your backside chewed up,” he wrote in support.

According to Craig, New Zealand is home to no fewer than 18 native sandfly species. While the majority are believed to feed either on honey dew and flower nectar or on the blood of birds, three species have developed a taste for human blood. “The most common of these scourges, Austrosimulium australense, is widely distributed throughout New Zealand,” Craig explained. “The second, A. tillyardianum, is found from south of Auckland to just north of Dunedin, and a third,” my nemesis A. ungulatum, “is restricted to the South Island, where it’s concentrated on the West Coast.”

It’s only the female that does the biting—though her lust for blood is far from wanton, Craig was quick to add. An unfed female can lay up to 12 eggs, but if she has managed to steal just one drop of our protein-rich fluids, she can produce ten times that number. On a full meal, she may leave behind many hundreds of successors.

What the males live on is mere speculation. “No one in New Zealand has ever seen a male sandfly feed,” admitted Landcare Research scientist Trevor Crosby (the very same who sustained the one-bite-per-second sandfly onslaught at Jackson Bay). Not many people have, it seems, seen a male sandfly do anything at all. Although they emerge from their pupae at the same ratio as their bloodthirsty female counterparts, they disappear shortly thereafter. Professor Craig isn’t surprised by this. “Too much screwing around,” he suggested, indicating that the only reason male sandflies are required is, perhaps, for their sperm.

Another myth is that sandflies suck. They don’t. “While mosquitoes have modified mouthparts that pierce the skin and draw up blood in much the same fashion as a hypodermic needle,” Craig informed me, “a female sandfly instead draws blood by using her knife-shaped mouth to slash your skin.” She then proceeds to lap up the resulting well of blood, a process scientists refer to as “pool-feeding”.

The most important implication of this is that no matter how long you wait, you will never be able to make a sandfly burst by stretching your skin as it’s dining on your arm.

The actual wound, which on the scale of things is pretty tiny, is not what causes the victim so much grief—it’s what the sandfly dribbles into it. To prevent her meal from clotting, a sandfly infuses the cut with a powerful anticoagulant called histamine, as well as agglutinins that prepare the blood for digestion in her stomach. It’s this chemical cocktail that we react to.

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A flick through the history books reveals that one of the first Europeans to discover the potency of sandfly saliva was Captain James Cook, the very person who most likely also gave sandflies their name (elsewhere in the English-speaking world they’re known as black flies). He used the term to describe the unknown plague that mercilessly tormented his crew during a six-week stay in Fiordland’s Dusky Sound. “Wherever they light,” Cook wrote in his journal in May 1773, “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.”

I, too, have borne witness to the little varmint’s lasting torment. Three years ago, I was called to help locate an after-hours pharmacy for an Australian friend who’d spent several days on the West Coast. The attack hadn’t been severe, yet her arms were very swollen. The actual bites had turned into solid, raw lumps, plasma oozing from where she’d scratched in a vain attempt to subdue the effect of the allergens. By breaking the skin, she’d created the perfect conditions for secondary bacterial infections.

According to immunology expert Frank Griffin, such an allergic reaction is no surprise. Our bodies have evolved mechanisms to help us combat parasitic infection, and fluid-filled blisters followed by hard itchy nodules just happen to be the uncomfortable effects of those responses. After consistent re-exposure, however, the body’s reactions to the allergen diminish.

In light of my own current sandfly-oriented mission, this was music to my ears. Although I now live in Dunedin, where the biting varieties are deemed to be “seldom a nuisance”, I grew up near Nelson, where they certainly were. Perhaps I was desensitised.

Griffin was quick to burst my bubble. “It takes about 10,000 bites to desensitise an individual,” he told me. I doubt I’ve been exposed to that many. “Even if you were,” Professor Craig later added, “each sandfly species has its own unique combination of allergens. It might not have been Austrosimulium ungulatum, that nasty West Coast species, that you were exposed to.”

Craig also pointed out that any suffering I was going to face during my encounter depended not just on the extent of my allergic reaction, but also on the number of sandflies that would bite me on the day. “We’re getting into pretty messy territory here,” said the professor, “but there have been suggestions that sandflies prefer some people over others.” Could it be that my genes weren’t “weak”, as my partner Peter had claimed, but simply made me more desirable to things that bite?

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The walk into Stafford Hut from Jackson Bay isn’t long—it takes only four hours one way. Yet from the moment you leave the carpark, it’s like stepping into another world. The towering canopy of moss-laden beech trees, the ponga and blechnum ferns, everything is green, lush, dripping and wet—exactly the kind of conditions that a small insect such as Austrosimulium ungulatum thrives in. To avoid dehydration, A. ungulatum can be active only when the relative humidity exceeds 60 per cent—not uncommon in a place such as Fiordland, where it rains almost two days out of three.

Although A. ungulatum will find you almost anywhere in the western wilderness, there is one type of habitat it prefers over any other—and where the bite rate is higher than anywhere else. That is at the edge of the forest adjacent to a stream or river. Throw in a beach for good measure (seals and penguins are, after all, what the biters largely fed on before humans arrived) and you’ve found it’s prime real estate. Such as the location of Stafford Hut.

As soon as I stepped into the hut I knew I was in trouble. Someone had gone to the effort of installing insect mesh across the windows. Not that it worked—what I’d taken for black paint on the windowsills turned out to be hundreds of mummified sandflies. A flick through the visitors’ book didn’t allay my fears: a number of visitors had dedicated their precious little space in the “comments” column to frustrated complaints. “The sandflies have an extreme attitude problem,” a hiker from Christchurch noted, and “Trop de sandflies!” exclaimed another, emphasising her point with a frowny face.

It didn’t take A. ungulatum long to find me either.

I had no intention of baring my bare flesh to the scourge just yet, but the immediate necessity of removing wet boots and clothes did give me a chance to test Craig’s theory on differential attraction. Within minutes, a large sandfly entourage had gathered around me, landing on my clothes and biting me on the top of my head. In contrast, I could count on my fingers the number of sandflies buzzing around my partner. I was, it seemed, simply more appealing.

My results are similar to those of a much more rigorous experiment conducted in Canada, which involved a large group of scantily clad people standing in a big field in the heart of sandfly country. When the researchers crunched the numbers, they indeed found “significant differences” in the number of sandflies that landed on each person. While some scientists suggest that differences in people’s body heat or odour could be at play, the academics in charge of the study hypothesised that differences in attractiveness depend on how much carbon dioxide each of us exhales.

That’s because, to a hungry sandfly, carbon dioxide is like the smell of freshly baked bread. Just as we follow our nose to the oven, sandflies detect and locate their prey by following the carbon dioxide plume that we all leave behind us.

But there’s a twist. Once a sandfly gets to within about six to seven metres of its target, it switches to visual mode. To home in on a suitable landing site, a hungry female makes use of her ability to distinguish differences in contrast between her prey and its background.

Which is the very reason that travel guides suggest you pick your wardrobe carefully before you step outdoors. “Don’t wear dark-coloured clothing,” they warn. Others let you choose your own level of risk. “Certain colours are more attractive than others,” a particularly thorough advice page reads. “As a rule, black, blue and red seem to be the most attractive, followed by brown, purple, maroon and dark green.” In contrast, “white, yellow, mid-grey and green are not as attractive”. Another advice column goes a

step further, recommending you use your friends as decoys by enticing them to dress in dark apparel while you slip into something a little lighter.

“It sounds weird, but it works,” admitted Te Anau–based Department of Conservation officer Ross Kerr. A few years ago, he and a group of colleagues were flown in to a remote part of Fiordland between Dagg and Breaksea Sounds to control marram grass near the mouth of the Cole River. “From above, it looked so delightful, but it was so deceiving,” Kerr recalled. As soon as the wash of the helicopter was gone, the sandflies that descended on the group were so thick that one man ran straight into the surf. “I remember asking a crew member to pose so I could get a good photo of him. Within two minutes, the back of his green overalls were black. From then on we wore nothing but white—white overalls, white gumboots and white beekeepers’ hats. We looked like we were from another planet—but when you’re faced with that many sandflies you simply don’t care.”

Wearing light apparel is just one of a long line of weird and wonderful attempts at keeping sandflies at bay. The early Maori sought help from Mother Nature, rubbing ngaio leaves onto their skin. European settlers were a little more experimental. For example, in 1892, the Minister of Public Works—Richard Seddon, who would later become Premier—decided to smear himself with camphorated lard, which he claimed worked well. South Island lighthouse keepers painted their doors with kerosene, and some recommended that settlers swallow spoonfuls of the combustible liquid so that the oil could ooze from their pores and thus repel the biters.

Fiordland pioneer Richard Henry, whose camp was infested with sandflies “in such numbers that they could bleed a man to death in a few hours if he had a large surface exposed and neglected them”, designed a clever contraption he called his “sandfly miraculum”. Henry smeared fat on a warm chimney, trapping thousands of the little beasts, which then slid down to be duly eaten by weka.

Later, people noticed that sandflies had no major natural predators, and decided to put that right. The earliest attempt at biological control was carried out in the 1930s by André Tonnoir of the Cawthron Institute in Nelson. After 10 years of searching for a suitable candidate, Tonnoir found what he was looking for: a group of dragonfly larvae native to rivers near Canberra, Australia, which were known to feed on resident sandfly larvae. He arranged for about 1700 of these sandfly predators to be sent to him, the majority of which he released into the Matai River in Nelson. This location was something of a poor choice. Yes, the water contained plenty of immature sandflies, but few of them were of the species that trouble humans. Not that it mattered—the dragonfly failed to establish anyway.

In 1983 and 1985, two New Zealand scientists working independently of each other had another crack at biological control. This time, efforts were concentrated on the bacterium Bacillus thuringiensis israelensis (Bti), which forms crystals that destroy the sandfly’s stomach lining. Bti was already being used to effectively control biting insects in Africa, and researchers closer to home found that the bacterium worked equally well in killing sandfly larvae in the lab. Based on these results, they suggested that the control agent might be “economically feasible in sensitive tourist resorts”. Others didn’t think it would be, and it, too, fell by the wayside.

Which brings us to the present day. Walk into a camping store and a prospective tramper will be dazzled by the choice of sandfly repellents. Candles, coils, lantern-shaped zapping devices, vitamin B tablets, ointments, sprays, lotions, roll-ons, each catering for any season, skin type and expected level of insect exposure. The active ingredients contained in these miracle cures are just as mind-boggling: citronella, permethrin, neem oil, bog myrtle, DEET—many of which are often more harmful than the threat they protect against. DEET, for example, strips paint, melts plastic and can cause life-threatening allergic reactions.

But these sandfly deterrents were not invented just for us. More than 2000 sandfly species swarm the globe—and we’re certainly not the only ones with biters. In fact, our resident populations seem almost benign compared to the little critters elsewhere.

Spare a thought for Canada, home to no fewer than 165 sandfly species. In the northern provinces, the little beasts are often so thick and relentless that keeping livestock is impossible.

Bulls get their scrotum bitten so badly that they refuse to mate, and harassed cows will not let calves suckle their udders. Driven to desperation, the animals clump together, don’t feed, lose condition and die.

Humans, too, are often driven mad by the little blighters, and Canadian trade unions have gone so far as to negotiate contract clauses that allow workers to stay at home when sandfly densities reach epidemic proportions.

Even worse off are the inhabitants of Africa and Latin America. Here, millions of people suffer from river blindness, a disease caused by a parasitic worm of which sandflies are the main vector. Before widespread eradication programmes were put in place, thousands of square kilometres of fertile river land lay abandoned—not to mention the personal suffering of those affected by the disease.

In contrast, the worst sandfly populations in New Zealand are restricted to remote areas, and none of our species carry diseases that affect humans—although, interestingly, that rule doesn’t apply to all animals. Some native sandfly species (including A. ungulatum) act as vectors to Leucocytozoon, a type of avian malaria that affects Fiordland crested penguins.

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Back at the Stafford River, I was busy wading through knee-deep, glacially cold water looking for Coke bottle-shaped specks. This is, I’d been told, what immature sandflies look like.

Like mosquitoes, sandflies start life in water. But unlike their nocturnal brethren, which favour quiet backwaters such as puddles and brackish swamps, sandfly larvae like it rough, seeking out the most fast-flowing area of a river or stream. Once they’ve latched on to a suitable rock, they leech their way to the very top, stick their bottom firmly in place by secreting a special type of glue, and lie back into the current.

“Sandfly larvae are filter feeders,” stream ecologist Katha Lange had explained to me one afternoon in her lab. “They simply sit and wait for their food to flow past them. When it does, they capture it using these big fans. See?”

I was surprised to see that the two Austrosimulium larvae under the microscope bore an uncanny resemblance to the grass grubs I occasionally dig up in my garden, just darker and much, much smaller. To the untrained eye, the only other obvious difference seemed to be that their heads were adorned with two prominent, antler-shaped structures. “In the water, these fold out and act as a net,” Lange told me. “Once in a while the larva will bring its fans forward and clean them off.”

When it comes to their lifecycle, sandfly larvae are similar to butterflies. Just as caterpillars are the main feeding stage in the life of a butterfly, sandflies actually do the bulk of their feeding as larvae in the river before they metamorphose into adulthood. When they’ve had their fill, the sandfly pupates in a cocoon-like structure and undergoes a complete body transformation. A newly formed adult that is about to hatch from its cocoon will form an air bubble around itself and rise to the surface, ready to fly off. Most sandflies, it turns out, hatch at dawn. This also happens to be the time when they’re at their most ravenous—as I was about to find out.

Clenching my teeth, I stepped out of the hut into the early-morning cold and rolled up my long john legs and sleeves to expose a virgin ground of goose-pimpled limbs. It didn’t take the little bloodhounds long to find me. My partner and I had agreed that I could fend them off for four minutes until a suitably large entourage had sniffed me out and were buzzing around me, then let them do as they pleased for the final 60 seconds. Clothing out of the way, the first six-legged little ninja touched down and scampered around my leg before tipping forward to draw blood. It was soon joined by another. And another. It was like being pinned down in the dentist’s chair, enduring an uncomfortable and ongoing torture. By the time Peter called “Time!” 21 sandflies were firmly latched to my legs, having breakfast. About the same number were busily running around, about to do the same.

It took about half an hour for the swelling to appear, large unevenly shaped lumps. By midday, they’d reduced to modest red spots. The itching started in the middle of the night, just as intolerable as Captain Cook had described.

However, in the scheme of things it was a small price to pay for visiting one of New Zealand’s most beautiful tramping destinations. Better still, I now have an incentive to return—there are only 9979 bites to go before I’m fully desensitised to the scourge of the West Coast. Now that’s an incentive programme.