The Encephalitis Mosquito

The Culex tarsalis mosquito lays its eggs in groups or “rafts” on the surface of standing water.  Its breeding habitat includes ditches, rice fields, wetlands and duck clubs. This mosquito transmits viruses that cause encephalitis in humans and horses, including West Nile Virus.  These mosquitoes feed primarily at dawn and dusk.  It readily bites humans, but prefers to feed on birds.

The Western Malaria Mosquito

The Anopheles freeborni mosquito is another standing water mosquito.  It lays its eggs directly on the surface of stagnant or still water where they hatch into larvae.  Breeding sites include ditches, rice fields, rain pools, wetlands and duck clubs.  This mosquito can transmit the parasite that causes malaria in humans.  Bloodmeals are taken primarily at dawn and dusk.  Midway through winter, on warm days, this mosquito often becomes bothersome as it comes out of hibernation or “diapause” and attempts to obtain bloodmeals for survival until spring when it can lay its eggs.

The Western Treehole Mosquito

The Aedes sierrensis mosquito is a flood water mosquito.  The female lays her eggs individually in rot holes that form in some trees.  As spring rain or irrigation water fills treeholes, eggs are stimulated to hatch.  Aedes sierrensis adults do not fly far from the source where they hatched.  This mosquito can transmit canine heartworm parasites and can be a severe pest of humans.  They will bite anytime of day, even in full sun, and are most common in early spring.

The Wetlands Mosquito

The Aedes melanimon mosquito is a floodwater mosquito.  The female lays eggs singly (one at a time) on damp or muddy soil.  Eggs may lay dormant for long periods of time until stimulated to hatch by rain or flood water.  This mosquito can become involved in the encephalitis transmission cycle.  It is commonly found in irrigated pastures, intermittently flooded duck club ponds, and other sources that periodically or occasionally flood or hold water.  Bloodmeals are taken any time of day, even in full sun.

The House Mosquito

The Culex pipiens mosquito is a standing water mosquito that lays its eggs in rafts.  It prefers to breed in foul water and water found in containers.  Some common places it breeds include catch basins and other sumps, tires, roof gutters, uncovered boats, ornamental ponds and fountains, neglected swimming pools and hot tubs, barrels and other artificial containers.  Although it prefers birds, it commonly enters houses in search of a bloodmeal, often disturbing and biting people as they sleep.  Culex pipiens is another competent WNV vector.

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