House Mosquitoes Culex Pipiens

General Information 

This species is commonly called a "house mosquito" because of its close relationship with mans environment and its habit of entering into houses and sometimes even breeding in indoor containers.

Culex pipiens is a light brown, medium sized mosquito with a blunt tipped abdomen (body).  There are narrow white bands on the body segments but none on the legs or proboscis (beak or biting mouth parts).  Males resemble the females, but are easily recognized by their bushy antennae.

This is the most common mosquito species in the world.  It is also widespread throughout the U.S. and Northern Utah.

Life Cycle 

Mosquitoes have four distinct life stages as seen in the illustration.  The first three stages of Culex are spent in the water.  An adult female lays about 150 - 200 eggs in clusters called rafts, which float on the surface of the water until they hatch in one to two days.  The female usually prefers laying eggs in standing, somewhat polluted water.  Around your home typical water sources include: gutters, unused swimming or wading pools, and wheel barrows.  A wide variety of other water sources may also be infested with the aquatic stages of this common mosquito.

The eggs hatch into larvae ("wigglers") which feed on small organic particles and micro-organisms in the water.  Culex larvae hang from the water surface by the tip of their tail (siphon) when they feed, or they may feed along the bottom, but must return to the water surface to breathe.  About 4 to 6 days are required for larval development.  At the end of the larval stage the mosquito molts and becomes the aquatic pupa ("tumbler").  The pupa is active only if disturbed.  This is the "resting" stage where the larval form is transformed into the adult.  This takes about two days during which time feeding does not occur.  When transformation is completed, the new adult splits the pupal skin and emerges at the surface.  Under optimum conditions, development from egg to adult takes about a week.  However, all mosquito developmental times are dependent on the temperature and nutrients in the water. 

These mosquitoes may live for two or three weeks in the summer, but under cooler conditions the females may live for several months.  In areas of moderate climate, larvae may be found in every month of the year.  In areas with cold winters this species usually passes the winter as hibernating females in protected natural or artificial shelters such as cellars, outbuildings, wood piles, caves, culverts, etc.

Habits 

Female "house mosquitoes" readily bite man, but birds and other mammals are considered the preferred blood host.  This species bites under low light intensity or in the dark, tending to seek entry to homes and resting in darkened areas when the light is bright.  Children and babies are most susceptible, often covered with numbers of reddened marks for many days following the biting period.  To humans, their humming at night  is an added irritation to the bite and sleepless night.

Where large populations exist, male swarming flights may be observed around twilight.  Mating may take place in conjunction with the male swarms.  Males feed on nectar and plant juices.  Females may also feed on plant juices, but must have a blood meal in order to produce eggs.

The House Mosquito tends to remain within a block or two of where they hatch.  However, when breeding sources are large and go untreated, females, may cause complaints several miles away.

Economic and Medical Importance 

These "house mosquitoes" are primarily a domestic nuisance, but may affect industrial and agricultural production in certain situations.

In other areas of the country House Mosquitoes are known to be vectors (carriers) of St. Louis Encephalitis.  They also transmit the organisms causing bird malaria, fowl pox, and heartworm of dogs.  House Mosquitoes also serve as vectors of filariasis in tropical areas of the world.

 Ornamental Pools

Has your ornamental pool been inspected this season by a mosquito abatement inspector?

If not, call and report the location of the pool.  A trained inspector will give you expert advice on how to care for them.  The pool will be stocked by the district with mosquito-eating fish.  Inspection and stocking fish will be made without charge.  Call 544-3736 today.

Western Tree Hole Mosquito Aedes sierrensis


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General Information 

The western tree hole mosquito is a serious pest and the most efficient vector (carrier) of dog heartworm disease in Davis County.  The mosquito receives its name because the immature stages develop in water of rot cavities in tress and because it is found only in the western U.S. This species is common throughout California and parts of Oregon, Washington, British Columbia, Idaho and Utah.  It was discovered in Utah, in 1965, along the Weber River.  It is now found throughout Davis County.

The Mosquito Abatement District-Davis County (MAD-D) has an on-going summer program to control this mosquito.

Life Cycle

All mosquitoes have four life stages: egg, larva, pupa and adult.  The adult female lays eggs individually on the damp inner walls of rot cavities or holes in trees in late spring and summer.  The eggs will remain unhatched until the tree hole retains enough water to flood the eggs.  The tree hole flooding can be caused by rainstorms or by lawn sprinklers spraying against trees.  The larval and pupal stages occur in the water with larvae eating decaying plant material.  Development from egg to adult is about three weeks. In hot weather development this process can be much more rapid.

The adults can be pests as early as April and continue until the first frost of fall.  Individual adults may live for two months or longer.

Where They Are Found

In Davis County, this mosquito is found predominantly in water filled cavities of the maple tree, but may also be found in other trees such as box elder, linden, sycamore, elm, cottonwood, and golden- rain trees.  Tree holes may vary in size from on forth inch to more than a foot in diameter at the opening and may occur from the base of a tree to several feet up.  Even a small tree hole can contain hundreds of larvae.

The adults of this species remain in shady, humid areas within 100 feet of the tree hole in which they emerge.  They prefer to stay outdoors and rarely enter houses.  The females are attracted to humans and their pets by the carbon dioxide given off during breathing.  Females will bite any time during the day, but are especially aggressive at sunset.

Culex Tarsalis Mosquito 


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General Information

This species is referred to as an "encephalitis" mosquito because it is the primary vector (carrier) of encephalitis viruses in the western United States.

C. tarsalis is a dark bodied, medium-sized mosquito with a prominent white band on its proboscis (beak) and white bands on the tarsi (feet).  It is further characterized by a white stripe on the sides of the rear legs and dark inverted V's on the underside of a blunt-tipped abdomen.  Males resemble the females except they have bushy antennae and long palpi on their head and "claspers" on the tip of their abdomen.

This is the most widespread mosquito species in California.  It occurs from Mexico into Canada and in the western, central, and southwestern United States.  It has been recovered from sea level to about 9,000 feet.

Life Cycle

Mosquitoes have four distinct life stages as seen in the illustration.  The first stages of Culex (egg-larva-pupa) are spent in the water. Females usually prefer to lay eggs in clear, standing water sources.    These include rain pools, marshes, reservoirs, pools, rice fields, irrigation tail waters, ditches, and domestic sources.  Although this species prefers clear, standing waters, it is sometimes found in vegetation along stream margins and in polluted sources.  Maximum populations usually occur in late summer.

These mosquitoes may live for two or three week sin the summer, but under cooler conditions the females may live for several months.  In areas of moderate climate, larvae may be found in every month of the year, but in areas with cold winters this species usually passes the winter as hibernating females in protected natural or artificial shelters such as cellars, outbuildings, wood piles, caves, culverts, and rodent burrows.

Habits

The females of this species are moderate but common biters of man, attacking at twilight and after dark.  Adults will enter dwellings seeking a blood meal, however, they seek shelter during the daytime.  Although they feed on man and domestic animals, this species appears to prefer the blood of birds.  Males do not bite, but feed on nectar and plant juices.  Although capable of moving many miles in dispersal flights, adults are most commonly found near their aquatic habitat.

Economic and Medical Importance

This species is the most important known vector of Western Equine Encephalitis (WEE) and St. Louis Encephalitis (SLE). From a disease standpoint, this is currently the most important species of mosquito in the State.

Where possible, the best approach is to prevent mosquitoes from breeding by eliminating or modifying breeding sites.  This may be accomplished by such actions as filling, dumping, ditching, or draining the source.  Rarely is this species found in various containers around the home, but these should be emptied of standing water.

Biological Control

The stocking of mosquito fish, Gamibusia affinis is often an effective control measure in sources such as fish ponds, pools, and watering troughs.  Other biological control measures are currently being investigated.

Chemical Control

Due to the often complex environmental interrelationships of some ponds, chemical control should only be practiced by trained mosquito abatement or health department personnel.  These officials have knowledge of the proper compounds and application techniques to assure minimal environmental side effects.  Public health agencies are often able to provide information and assistance where organized mosquito control programs are unavailable.  

It is important to remember that chemical control provides only temporary relief and is used by public agencies until other measures can be implemented.

Commonly available insect repellents may be useful if it is necessary to be in an area where very large numbers of this species exist.