Mosquito Facts

   Simple Facts 

• There are over 2500 different species of mosquitoes throughout the world, of which 150 species occur in the United States.
• A single female can lay over 200 eggs at a time. Mosquito eggs can survive for more than five years.
• All mosquitoes need water to complete their life cycle.
• Not all species bite humans; some prefer birds, others prefer horses, and some will even bite frogs and turtles.
• Only females take blood; males feed only on plant nectar.
• Mosquitoes can fly considerable distances; some species remain close to their larval habitats while others can fly 20 miles or more.
• Mosquitoes do not develop in grass or shrubbery, although adults fequently rest in these areas during daylight hours.
• Mosquitoes are responsible for more human death than any other living creature.   

    Life Cycle of a Mosquito 

Mosquitoes of different species lay their eggs in a variety of water sources that range from small containers to vast expanses of marshland. The larval stage is always aquatic and shuttles from the subsurface where it filter feeds on micro-organisms to the surface to obtain oxygen through a snorkel-like breathing apparatus. The pupal stage does not feed but unlike most Insect pupae is extremely active. The adult emerges from the pupal case using air pressure and assume a terrestrial existence.

Drawing by Brett Crans, Rutgers University

Stages of Development:  All mosquitoes goes through four separate and distinct stages of development: Egg, Larva, Pupa, and Adult, and spend their larval and pupal stages in water. Each of these stages can be easily recognized by their special appearance.

Egg :  Culex mosquitoes lay their eggs on the surface of fresh or stagnant water. The water may be in tin cans, barrels, horse troughs, ornamental ponds, swimming pools, puddles, creeks, ditches, or marshy areas. Mosquitoes prefer water sheltered from the wind by grass and weeds.  Culex mosquitoes usually lay their eggs at night. A mosquito may lay a raft of eggs every third night during its life span.  Culex mosquitoes lay their eggs one at a time, sticking them together to form a raft of from 200- 300 eggs. A raft of eggs looks like a speck of soot floating on the water and is about 1/4 inch long and 1/8 inch  wide.  Tiny mosquito larvae emerge from the eggs within 24 hours.

Larva :  Mosquito larvae, commonly called "wigglers", must live in water from 7 to 14 days depending on water temperature.  Larvae must come to the surface at frequent intervals to obtain oxygen through a breathing tube called a siphon;   most larvae can be found hanging from the water surface. The larvae eat algae and   microorganisms which live in the water, as well as organic matter in the water.   During growth, the larva molts (sheds its skin) four times. The stages between molts are called instars. At the 4th instar, the larva reaches a length of almost 1/2 inch. When the 4th instar larva molts it becomes a pupa.

Pupa: The pupal stage is a resting, non-feeding stage. This is the time the mosquito turns into an adult. It takes about two days before the adult is fully developed. When development is complete, the pupal skin splits and the mosquito emerges as an adult.  Mosquito pupae, commonly called "tumblers," must live in water from 1 to 4 days, depending upon species and temperature.  The pupa is lighter than water and therefore floats at the surface. It takes oxygen through two breathing tubes called "trumpets." When it is disturbed it dives in a jerking, tumbling motion and then floats back to the surface. The pupa does not eat.

Adult: The newly emerged adult rests on the surface of the water for a short time to allow itself to dry and all its body parts to harden. The wings have to spread out and dry properly before it can fly. When adult mosquitoes emerge from the aquatic stages, they mate, and the female seeks a blood meal to obtain the protein necessary for the development of her eggs. The females of a few species may produce a first batch of eggs without this first blood meal. After a blood meal is digested and the eggs are laid, the female mosquito again seeks a blood meal to produce a second batch of eggs. Depending on her stamina and the weather, she may repeat this process many times without mating again. The male mosquito does not take a blood meal, but may feed on plant nectar. He lives for only a short time after mating.

Varied Habitats:   As noted, the females of some mosquito species deposit eggs on moist surfaces, such as mud or fallen leaves, that may be near water but dry. Later, rain or high tides reflood these surfaces and stimulate the eggs to hatch into larvae. The females of other species deposit their eggs directly on the surface of still water in such places as ditches, street catch basins, tire tracks, streams that are drying up, and fields or excavations that hold water for some time. This water is often stagnant and close to the home in discarded tires, ornamental pools, unused wading and swimming pools, tin cans, bird baths, plant saucers, and even gutters and flat roofs. The eggs deposited on such waters soon hatch into larvae. In the hot summer months, larvae grow rapidly, become pupae, and emerge one week later as flying adult mosquitoes. A few important spring species have only one generation per year. However, most species have many generations per year, and their rapid increase in numbers becomes a problem.

About the Culex Mosquito:  Culex pipiens, or northern house mosquito is the most common species of mosquito found in urban areas. It appears to be primarily responsible for transmission of WNV to humans and birds, as well as to other mammals.  Culex mosquitoes are painful and persistent biters which prefer to attack at dusk and after dark, and readily enter dwellings for blood meals. Domestic and wild birds are preferred over man, cows, and horses.  Culex are generally weak fliers and do not move far from home, although they have been known to fly up to two miles. Culex usually live only a few weeks during the warm summer months. Those females which emerge in late summer search for sheltered areas where they "hibernate" until spring. Warm weather brings them out in search of water on which to lay their eggs.

 Back to West Nile Virus Homepage