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Yacht Charter Guide

Sand Fly Defense

By Captain Scott Fratcher

New Zealand, Canada and many other countries abound with the world's finest natural scenery. They have glaciers, lakes, mountains, rivers, stunning harbors and a healthy population of sandflies.

For those that have yet to meet the sandfly they are a small black gnat like creature with a humped back. Traveler blogs refer to the sandfly as "hated, filthy, and annoying." Scientists often downgrade the sandfly to a "nuisance" category only because it is rare for anyone to die from a sandfly attack. Still some medical literature refers to sandfly bites as causing-

  • · Acute discomfort,
  • · Irritation, and
  • · Severe local reactions

In the last few years many advancements have been made in managing travel in sandfly prone areas. With a little forethought and planning we can fully enjoy the natural environment while living in harmony with the infamous sandfly.

Sandfly attack

Sandflies typically arrive one or two at a time. They quickly build to a swarm encircling the victim. They seek exposed skin where the female saws a hole through the outer derma with a mouth shaped like a bread knife. Bleeding begins and a collection of blood is formed.

The sandfly drools while it laps up the blood pool. This drool contains a powerful anti coagulant called histamine that prevents the blood from clotting. Agglutinins that prepare the pooled blood for digestion are also deposited on the skin. It is this histamine and agglutinins mix that causes the red bumpy reaction in the victim's skin.

Amazingly sandflies tend to feed on tourists and new arrivals while locals seem to build some type of internal resistance to sandfly bites. It may be that locals receive the same number of bites, but their body has built a resistance to the histamine reaction. It is this resistance that allows some people to remain unaffected by the sandfly bites while others swell with red puss filled sores.

Sandfly defense plan

Sandfly swarms can arrive quickly. By building a sandfly defense plan a sandfly swarm can be made tolerable. The plan should contain clothes that are instantly donned and actions that are taken.

A sandfly defense kit should contain-

  • · A hooded sweatshirt
  • · Bandana
  • · Pants that can tuck into socks
  • · Bug repellant
  • · A hat that has bug repellant applied

Remember to-

  • · Close up the boat, camper, and car.
  • · Take care of the kids
  • · Light the citronella candles

Ten Sandfly defense tricks

1. Wear a hat covered with some type of sandfly deterrent. Goodbysandfly, tea tree oil, eucalyptus oil and citronella oil all have had success in repelling sandflies.

2. Consume vitamin B. This defense works for mosquitoes and sandflies alike. Vitamin B capsules, Marmite, Vegemite, and brewers yeast all contain high levels of vitamin B that will considerably help in deterring sandflies. The effects of vitamin B can most easily be seen when standing with a group of non-vitamin B eaters.

3. Bug protect your anckles with socks or some bug repellant. Sandflies tend to start their attack at the ground level and work upward.

4. Wear light colored clothes. Sandflies are attracted to dark clothes.

5. Walk. Sandflies are very slow creatures. As long as you are moving they can't swarm.

6. Keep your car, caravan, and boat closed up. Sandflies are notorious for their ability to find openings to enter and lie in wait.

7. Boat's can anchor offshore a short distance to minimize the sandfly effect.

8. Plan the day to spend sunrise and sunset geared up for sandfly defense.

9. Sandflies are attracted to heat. Turn off needless lights during dusk.

10. Sandflies can follow a carbon dioxide trail hundreds of meters. If dense bush is located directly downwind consider moving.

Color of clothes

Testing has shown that light colors don't attract sandflies nearly as much as dark colors. Becky Cashman of a producer of natural sandfly repellent says, "The single best defense against sandflies is to cover up with light color clothing."

This is because sandflies close in on their prey by use of built in infrared sensors. White does not reflect as much heat as dark colors. Wearing white clothes can be especially effective if others are wearing dark colors nearby.

What to do when the sandflies are in your camper or launch

Sandflies have an uncanny way of filling empty areas. Opening the door to a living space can allow dozens of sandflies to enter where they will lie in wait till dusk or dawn to feed.

Sandflies make no noise when flying so a stealth dawn assault is inevitable. This is important as a sandfly attack while you sleep can produce over a dozen bites in a single morning. Over a week this can add up to a lot of red itchy bumps.

Segregate the living space

The first defense is to segregate the living space. Hanging mosquito nets between cabins helps reduce the spread. A mosquito net draped over a hatch, window, or door allows easy access, but prevents most sandfly entry. A mosquito bed net is an elegant solution for a peaceful nights sleep.

Quick sandfly eradication

Luckily sandflies are attracted to heat. A simple method of clearing sandflies from a living space is to turn on a single light. Force the sandflies into the air by walking through the cabin swinging a duster or magazine. Pay particular attention to the corners, and areas under shelves.

The airborne sandflies become attracted to the light and begin to circle. As the sandflies surround the light they become easy pray for a quick smash against the light housing.

Citronella candles

Citronella oil repels and even kills sandflies. Citronella oil lamps placed upwind can help to deter a sandfly attack. Citronella candles burned inside the vehicle or cabin a half hour before entry can kill most of the errant and hiding interior population. Remember to keep an eye on the open flame.

Other tactics

Opening back windows and taking a drive can suck the errant sandflies out of a vehicle or boat. Sandflies don't like heat. Closing up a vehicle or boat in the sun for a short period can kill the complete invasion.

Bites and how to deal with them

The first step to managing a sandfly bite is the application of an antiseptic. Goodbysandfly states,

Essentially your are dealing with three separate things-

  • · A protein in the saliva of the sandfly
  • · Any contaminants that the sandfly introduced to you via this bite
  • · A small wound.

Early cleaning and disinfectant goes a long way in reducing healing time. Becky even recommends the natural remedy of a bit of onion juice rubbed onto the bite as a way to reduce itching and healing time.

Another common herbal remedy for reducing the itch of bites is Chamomile tea, drunk as a tea or applied topically.

Squeeze or not

Some tourists claim it's better to squeeze the toxins from a bite. To find out I tested two bites side by side. One I squeezed once to remove the toxin while the other I left to it's own devices. Over the next few days it looked as if the closed wound would heal quicker, but by day seven the squeezed bite was looking cleaner. On day ten both bites healed completely.

Our in field testing dictated it was best to leave the bites to their own devices so the wound remains closed reducing the risk of infection.

New Zealand South Island sand fly population

While all coastal and river areas can be affected by the dreaded sandfly the most active concentrations are found along the west coast of south island and Fiordland. These areas also contain some of the most spectacular scenery to be found in New Zealand.

The sandfly density typically has a slight reduction in numbers during July and August. Sandflies tend to be the most vicious on cool, windlass days just before dusk especially near dense bush or stands of trees.

Sandflies thrive in humidity above 60%. Thus, we can expect sandflies to swarm just before it rains. Hot, dry days are nearly sandfly free.

To the traveler this means pay particular attention to the weather for predictions of overcast calm days with high humidity meaning it's time to take full sandfly precautions.

The incredible sandfly life cycle

D. A. Craig, a retired entomologist and renowned sand fly expert is currently studying sandflies in New Zealand. He explains that New Zealand has 18 sandfly species. Luckily only three species bite humans while the rest feed on penguins, bats, and other local animals. Of the three species that feed on humans only the female bites while the males feed in shady areas eating sap, nectar and other vegetarian meals.

The female wants to ingest blood in order form eggs. Without a blood meal a typical female can only lay a dozen or so eggs. Once the sandfly has eaten a full blood meal they can lay up to three hundred eggs two to three times in their life cycle. In other words a single female sandfly can produce nearly a thousand offspring. This helps explain the sandfly densities.

The sandfly copulates only once in a lifetime storing the male seed that re-fertilizes each new batch of eggs. The eggs are laid in running water clinging to mud, rocks or vegetation. Sandfly eggs take about ten days to hatch into small larva.

The newly hatched larva attach themselves by hooks on their bums to vegetation or rocks in calm flowing water. They extend a set of fans that filter the flowing water witch they feed upon.

Once fed, the larva forms a cocoon of silk where the larva, like a butterfly, soon becomes a sandfly. When the sandfly morph's or "hatches" from its cocoon it forms an air bubble. The adult sandfly enters the air bubble, rises to the surface perfectly dry, and flies away seeking blood.

Traditional remedies

Early Maori and settlers were plagued by sandflies. In defense some rubbed their bodies with rancid bacon fat, while south island lighthouse keepers painted their doors with kerosene. The Maori repelled sandflies with a mix of crushed leaves from the Ngaio Tree while some doused their bodies with Red Ochre.

In 1892 the Minister of Public Works smeared himself with camphorated lard, which he claimed worked well. Some ancient lour even reports early settlers actually swallowed a teaspoon of kerosene claiming the oil would ooze from their pours repelling sandflies.

Once bit Maori applied a juice from crushed Ngaio leaves or a juice made from the fronds of Rarauhe or Bracken Fern.

Future of Sandfly defense

Technology is helping the tourist enjoy his New Zealand experience. From new types of repellant, to electric bug zappers, advancements are made almost daily. Here is a selection of the latest innovations.

Insecticide clothing sold at now claims the first insect repellent apparel registered by the U.S. Environmental Protection Agency. BUZZ OFF contains permethrin, a man-made form of an all-natural insect repellent derived from the chrysanthemum plant.

Light manufactures are now designing bulbs that give off yellow luminous pigment that is reputed to repel insects, especially insects that are attracted to light. See

High-pitched noise has helped to repel insects of all types. A variety of manufactures now produce portable noisemakers just outside of the human ear response. They report a distinct reduction in insect swarms.

High voltage bug zappers are now common, with a portable tennis racket style available for those that wish for an interactive bug eradication experience.

Fine mesh helmets similar to those used by beekeepers are available to those who must continue to work in sandfly-infested areas.

As a last resort one can always fold up this magazine and swat the sandfly into oblivion.

Special thanks to Douglas A. Craig, Professor Emeritus, Department of Biological Sciences, University of Alberta, Edmonton, and Becky Cashman of Goodbysandfly.

Sandfly mysteries

D. A. Craig, is currently in New Zealand with Landcare research studying sandflies. The last sandfly revision was done over thirty-five years ago.

D. A. Craig poses three sandfly mysteries-

1. How do sandflies find there pray so far from breeding grounds?

2. What did the sandflies eat before humans arrived?

3. Are there more sandflies today than pre-human times since sandflies now have such a handy source of food?

Sandfly tidbits

Sandfly density can overwhelm local cattle due to anaphylactic shock. Even the human population is not immune. In Canada for example trade unions have negotiated into their contracts clauses that prevent work when sandfly densities reach epidemic proportions.

New Zealand sandflies don't carry any known diseases that effect humans. They do however carry a form of bird malaria that affects penguins.

Goodbysandfly reports it's better to open an upwind window in a living space. If you open the down wind window sandflies collect in the eddy created and enter the space. Simple net curtains can do wonders for keeping an inside space comfortable.

Sandflies are particularly susceptible to insecticides, but spraying has not seemed to reduce their population. One report from Columbia sent scientists to local homes where the inside walls were sprayed with insecticide. Test traps collected in the homes showed almost no reduction in sandfly population. It was thought the density of sandfly population in the bush was so great that they simply "re-filled" the "kill zone."

Tonga has no sandflies!


Call now to book a 2010 vacation

To visit stunning territory like this we have to deal with sandflies.

Gearing up means covering up

Future sandflies

Sandfly biting

Sandflies attach eggs to leaves

Cover up and hope for the best

Sandflies bite deep

Survival of the sandfly

Sandflies cover the tent top

Slap and be happy

Walking keep sandflies away

One night of bites

Sand fly territory

The trekking is great. The sandflies are not.








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