Modern studies of Simuliidae must take special account of this problem. Members of the family are usually called black flies, but in New Zealand they are widely known as sand flies. Bloodsucking is not a universal habit, but females of most species feed on warm-blooded vertebrates, often preferring either birds or mammals. Except in the Marquesas, where they can be a severe local scourge, simuliids are rarely more than a minor biting nuisance in the Pacific Islands. There is no evidence that black flies are involved in any human disease in Australasia or Oceania, but they are believed to play a part in the transmission of Onchocerca gibsoni , a filarial parasite of Australian cattle.
Early stages are aquatic and virtually confined to running waters.
Larvae and pupae are attached to submerged substrates, most often trailing vegetation, stones, or the fixed bedrock of cascades and waterfalls. Those of some Polynesian species have been found in an unusual microhabitat, lodged between closely packed fallen leaves trapped in water current. Surprisingly, simuliids have failed to colonize Tonga, Samoa, and Hawaii, island groups with flowing streams potentially able to support their development. Nearly all species from these areas belong to Simulium s. The Australian fauna, in addition to these 2 genera, contains a few primitive forms assignable to the Prosimuliini.