Midge flies belong to a group known as Diptera, or true flies. Their life cycle is important to humans because they are considered a commodity, meaning that they are raised for sale to anglers. These flies have a well documented life cycle as they have been successfully bred in captivity for many years.
Mating
Adult midge flies reproduce sexually and mate in flight. They tend to congregate in large swarms at the edge of waterways such as lakes and rivers just for this purpose. After mating, the female releases her eggs into to water while in flight, where they sink to the bottom.
Larvae
The eggs hatch and the immature larvae live along the bottom of the waterway, usually hiding amongst the vegetation in slower currents as they do not swim well. Some species will construct tubes out of the lake bottom material that will run perpendicular to the lake or stream bottom, pointing upward. The larvae that do this will spend all of their development time, up to pupation, in this tube. It is important to note that the larvae of a specific genus of midge fly, known as bloodworms due to their red coloration, are also used commercially as a fish food for small carnivorous and tropical fish.
Metamorphosis
After the larva completes its development, it is ready to enter metamorphosis. The larva will encyst itself in a hard shell and change into a pupa, where it will undergo metamorphosis and change into an adult. Completing this change process will take a few days to a few weeks depending on the species. The pupa will then begin its ascent to the surface of the waterway, the final step before emerging as an adult. It is during this stage that the midge fly is the most vulnerable as it creates a gas that it traps in its abdomen to help its migration to the surface. It is this gas that attracts the attention of hungry fish.
Emergence
When the pupa reaches the surface of the water, the casing around the pupa splits open down the back and the adult midge fly takes flight immediately. The flies are fully developed and will mate within 24-48 hours, completing the life cycle. The adults will die shortly after mating.
Significance
The midge fly is ecologically important in that is serves as a food source for many aquatic species, including trout and other game fish. The midge fly is also economically important as anglers depend on the availability of them for natural fly fishing.
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