Chironomids are two-winged flies of the Nematocera (or lower
Diptera). They look something like mosquitoes but do not have their
nasty habit of biting! At rest they can be distinguished from
mosquitoes by the raised front legs - mosquitoes raise their hind
legs.
Like mosquitoes, the immatures of most chironomids are aquatic.
Chironomids are of economic importance as fish food, indicators of
pollution or because they reach pest proportions in some areas,
particularly rice growing areas.
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In Australia these have relatively short life cycles - from 10 - 40
days and most breed throughout the year. The female lays her eggs
in a group as an eggstring or eggmass of up to 800 eggs (in C.
duplex), either directly into water or attached to plants or
stones at the water´s edge.
After a couple of days the eggs hatch as larvae, which are red in
colour due to the presence of numerous haemoglobins. This gives them
their common name of "bloodworm". The larvae go through
four instars. In the fourth instar polytene chromosomes develop in some
tissues, reaching their greatest size just before the larva pupates
in a silk-lined tube. After 2 or 3 days the pupa swims to the
surface and the adult fly emerges. Mostly the adults live only a day
or two - mating, laying their eggs and then dying. In many species
the males swarm before mating, often using trees or other high
objects (such as church steeples) as markers on which to orient the
swarm. Large numbers can look like smoke and on occasions have led
to false alarm calls for church steeples being on fire!
Some species can be readily reared or bred in the laboratory.