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Sandflies

New Zealand does not have any dangerous animals, but it does have the sandfly, mainly found on the west coast of South Island and peaking at Jackson Bay. SEE:Day 27 – Alexandra to Haast

Sand Fly

If you get bitten by tiny black flies it is likely that you have been the victim of what New Zealanders call sandflies (namu in Māori). Sandflies, like mosquitoes and other flies, are members of the order Diptera, and belong to the family Simuliidae. Sandflies are known as black flies elsewhere in the western world. NZ definitely does not have the worst biters, the Northern Canadian provinces have 165 versions, Australia has plenty and Africa's version carry deadly diseases.

There are 13 species in New Zealand, all belonging to the genus Austrosimulium. Only two species bite: the New Zealand blackfly (Austrosimulium australense), and the West Coast blackfly (A. ungulatum). At only 2–3 millimetres in length, they look the same to the naked eye.

Maori have a wonderful explanation for the sandflies existance, they claim that when the goddess of the underworld, Hine-nui-te-po, saw the fiords, she deemed them too beautiful to be modified by man, so realeased the black flying plague. Her ploy worked.

Distribution

Sandflies are found wherever there is flowing water and bush. They are often found at beaches, and at the edges of lakes or swamps. The New Zealand blackfly occurs in the North Island and around the coasts of the South Island. The West Coast blackfly is confined to the South Island, where it is a nuisance.

The West Coast and Fiordland are infamous for their sandflies. The terminus of the Milford Track, where trampers board the ferry to Milford Sound, is called Sandfly Point.

Early encounters

While surveying Doubtful Sound in the summer of 1851, Captain John Lort Stokes of the Acheron was tempted but resisted putting the names Venom Point, Sandfly Bay and Bloodsuckers Sound on the map, after encounters with the biting insects. Road builders on the Milford Road and Haast Pass suffered clouds of them. While surveying road routes near Haast in the 1930s, Alan Dawber played a game with his mates: ‘We used to compete with each other by baring our forearm to the sandflies, then when the first one made its presence felt, we would start killing them off one by one. I think the record was 64 before wiping the stinging mass clear.’

Life cycle

Sandflies breed in fast-flowing streams or rivers. Eggs are laid on rocks or plants around or below water level. Larvae hatch and collect food from the current, using foldable ‘nets’ that surround their mouths. These expand to catch passing organic particles, algae, and bacteria. The larvae pupate and spend around 12 days in this form, before emerging as flies at the water’s surface. The length of the life cycle varies, depending on the time of year, but averages around six to seven weeks.

Worth writing home about

The first instance of the word sandfly (rather than blackfly) for the New Zealand species is in the journal of James Cook. He came across the insects at Fiordland’s Dusky Sound, possibly at a sandy beach, in May 1773. His journal reads:

‘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.’

Only females bite

After mating, the female searches for a meal of blood – needed to produce eggs. (Little is known about the male, who is a vegetarian. he just seems to be around for his sperm) Females attack vertebrates such as penguins and other birds, bats, seals, domestic animals and humans. They pierce the skin, creating a drop of blood that they suck up, after she has infused the wound with histamines and agglutinins, its these that cause the reaction. A hungry female will only lay about 12 eggs, but after a feed will lay hundreds.

When do they bite?

Sandflies cannot see at night, so they seldom bite in the dark, and generally remain outdoors. Peaks in biting often occur when light intensity increases in the morning and decreases at dusk. The morning peak comes from young sandflies that have recently emerged from pupae, and the higher evening peak is often the result of sandflies taking blood after laying eggs earlier in the day.

Sandflies are most active in dull, overcast and humid conditions, when they may bite at a similar rate throughout the day, they need a humidity of at least 64%, which is not hard to achieve in Fiordland, where it rains on 2 days outer of every 3.

Avoiding Sandflies

Sandflies are attracted by CO2 which we all exhale, which is like smelly fresh bread to them. At about six metres distance sandflies turn to visual mode, the hungry female uses her ability to distinguish differences in contrast between her prey and the background. The point being wear light clothes. There are of course numerous sprays and roll-on products to deter sandflies, the NZ ones tend to be best, having been tested in situ. The other alternatives is to get 300 metres out at sea or climb 1500 metres up a mountain.

Information gathered from personal experience on our trip round South Island, from the government website and from New Zealand Geographic. [[http://www.nzgeographic.co.nz/]. An excellent Mag. it's great a small population can support a quality publication like this.

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terris_travelogue/south_island/sandflies.txt · Last modified: 2013/07/01 11:21 by art
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