Ecology: Simuliid adults are commonly known as ‘black flies’
Instream habitat: Larvae occur in fast flowing waters. They will not survive if removed from the main current as a slow velocity does not meet their requirements of filter-feeding and respiration. Larvae and pupae are found attached to submerged substrata, usually trailing vegetation, cobbles or fixed bedrock. However, pupae are often more numerous on the downstream side of rocks or towards the base of submerged plants, where the current velocity is less rapid.
Feeding ecology:Larvae are filtering collectors, extracting fine particulate detritus from the water as it flows past.
Habit: Larvae and pupae do not swim, they move around the substrata with a caterpillar-like motion. Larvae require a relatively clean substratum on which to secure a pad of silk strands that attaches them to it
Life history: Most of the following information comes from North American studies. The egg stage is the resistant stage of the life cycle for some species and can withstand desiccation, then hatch after a flood event. Duration of the egg stage varies from one day to nine or ten months depending on the species and water temperature. Larvae will remain at the hatching site if the substratum and food supply are adequate otherwise they will drift downstream on a silken thread to more suitable sites. The larval period varies from less than one month to six or seven months in over-wintering species. In warm waters, the larval stage lasts only a few weeks. Larvae pass through four to nine moults, typically seven. Early instars have a shorter duration than later ones and two moults per day may occur within fast growing species. Final instar larvae spin variously shaped silken cocoons that anchor and protect the developing pupae. Duration of the pupal stage varies according to water temperature, but usually lasts four to seven days. When an adult is ready to emerge its wings expand causing it to rise to the surface in a bubble of air. In most cases the adult immediately flies to a rest spot to allow its cuticle to harden. Mating can occur shortly after emergence or just before oviposition and takes place in flight or while landed. Females of some species require a blood meal for maturation of the eggs, either before or after mating. Females lay their eggs in a variety of lotic environments ranging from the smallest trickle to the largest rivers; the choice of habitat will vary with the species. Oviposition varies from the free distribution of eggs while the female taps her abdomen on the water surface during flight, or ovipositing while landed on wet surfaces such as grass trailing in the water, or crawling underwater to deposit the eggs.
Information Sources: Crosskey 1990, 2007, Colless & McAlpine 1991, Merritt & Cummins 1996, Bugledich 1999, Hawking & Smith 1997, Williams 1980, Bass 1998
Key to Genera: Mackerras & Mackerras 1949
Key to Species: Mackerras & Mackerras 1949 (Austrosimulium & Cnephia - partial)
Colbo 1976 (Simulium - partial)