Fly (Sandfly) Austrosimulium species
Order : Diptera
Common name: Sandfly, Namu., Black fly
Sandflys are a native species found throughout New Zealand. 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. The larvae of these sand flies live in both stony and weedy streams where they are attached to plants or rocks. They catch drifting food in their fan-like mouthparts. It takes a keen eye to see these insects without a magnifying glass, but sometimes they can be seen attached to surfaces by their rounded tail-end.
Eggs are laid on rocks or plants around or below water level. 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.
Only females bite. Like mosquitoes, the female after mating takes a blood meal to provide protein to develop her eggs. (Little is known about the male, who is a vegetarian.) 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. Prior to and during blood feeding, they inject saliva into the bodies of their source of blood. This saliva serves as an anticoagulant: without it, the female proboscis would quickly become clogged with blood clots. 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,
The anatomy of their feeding mechanism means that (unlike mosquitoes) they leave a large raised mark on the skin that is filled with damaged tissue and saliva (containing anticoagulants). This can cause certain individuals repeatedly exposed to their bites to become “sensitised” and trigger allergic responses. The direct impact on human health and wellbeing caused by midges is due to the allergens in midge saliva. These biting insects are an annoyance to humans, but are not likely to transmit disease.
The Maori created a legend wherein "the god Tu-te-raki-whanoa had just finished creating the landscape of Fiordland, it was absolutely stunning... so stunning that it stopped people from working. They just stood around gazing at the beauty instead. The goddess Hinenuitepo became angry at these unproductive people, so she created the sandfly to bite them and get them moving"