The Sandfly

If its Spring, Summer or Autumn in Arthur's Pass you will be introduced to the most abundant of native wildlife in New Zealand - the Sandfly...


Probably the most noticed of the Park's wildlife, the sandfly however spends a good part of its life in the swift waters of the streams, taking about 6-7 weeks in summer to develop from egg to adult. You will be pleased to know it is the female only of some species of sandfly that bite and draw blood.

Adults lay eggs on the downstream surface of rocks or vegetation underneath the water surface in swift streams.

Larvae anchor themselves to rocks. when first hatched larvae are about 0.5mm long and when mature 5 to 8mm long. They have hair like head fans which strain water for food particles. Larvae are mobile and are often seen in groups.

When ready to pupate the larva builds itself a small silken case attached to the rock. It then undergoes transformation to form an adult. Just before the adult emerges there is a build up of air between the pupal and skin and the adult. The pupal skin splits and the adult rides in the bubble of air to the surface and is able to fly immediately.


Just simply go outdoors and stand in one place for about 2 minutes, they will find you. When they bite they inject a very small amount of toxin to prevent your blood coagulating (clotting), this also acts as a very short-term anaesthetic. You generally know you've been bitten about 5 seconds after the act, which is generally too late !

If bitten, the may thing is NOT TO SCRATCH, as some people are allergic to the Sandfly toxin, and scratching spreads it via your bodies lymphatic system (chemical distribution system). Lumps and bumps may rise on your skin in areas that sandflies cannot reach.


  • Keep moving, Sandflies cannot fly long distances, and are awkward fliers.
  • Hope its a windy or cold day.
  • Wear long sleeves, trousers, socks, scarf.
  • Put on a citronella based repellent.
  • Climb above 1200 metres, or move away from streams and rivers.

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