Over thirty different species of mosquitoes representing six genera or groups have been recorded in the Edmonton area. These six groups share general similarities in their life cycles including the egg, four larval stages, a pupa and the adult.
In all cases it is only the adult female that feeds on blood, which is used as a source of protein for egg development. Regular energy requirements of both sexes are normally provided by flower nectar.
The predominant mosquitoes in Edmonton belong to the Aedes and Ochlerotatus groups. These mosquitoes typically lay eggs in dry or damp, low-lying areas that are subject to flooding from accumulations of precipitation. Winter is passed in the egg stage and larval hatching requirements distinguish two types: those that hatch in spring and those hatching later in the summer.
In the spring hatching species, flooded eggs are stimulated to hatch by depletion of the water's oxygen content, caused by a renewal of bacterial action in snow melt pools. Cool water temperatures promote relatively slow larval development, requiring as long as a month for completion of the aquatic stages.
The resulting adults, of which there is only one seasonal generation, normally begin to appear in early to mid-May. Adults of some species last to the end of August, but by mid-July most have normally died off.
Our major pest species belong to the previously mentioned summer hatching species, characterized by the highly successful Aedes vexans. In this species, flooded eggs hatch when the water temperature exceeds a critical point (about 10°C). Larval development may take as a little as five days, allowing this species to exploit extremely temporary bodies of water.
Adult females are persistent biters, capable of multiple summer generations and are known to disperse over great distances. Edmonton's heavy summer rainfall, combined with its gently rolling topography of poorly draining, clay-rich soils, create perfect conditions for the widespread development of huge populations of this particular species.
The other four groups of mosquitoes, Anopheles, Coquillettidia, Culex, and Culiseta exhibit a variety of life strategies. For the most part, eggs are laid directly on the surface of open water in the form of floating egg rafts. Hatching stimuli are of little significance.
Over-wintering in Anopheles, Culex and Culiseta mainly takes place in the adult stage by fertilized, non blood-fed females. This occurs mostly in animal burrows, rock piles and root cellars. In Coquillettidia, larval stages over-winter apparently without total loss of activity, restricting development to very permanent water bodies.