Mosquitoes and the Diseases They Can Carry Almost everyone has had the unpleasant experience of being bitten by a mosquito. Mosquito bites can cause severe skin irritation due to an allergic reaction to the mosquito's saliva; this is what causes the red bump and itching. But transmission of certain serious diseases, such as malaria, dengue fever and several forms of encephalitis, including West Nile virus, are a more serious consequence of some mosquito bites. Other animals, such as dogs and horses, are highly susceptible to mosquito-borne diseases, such as heartworms, eastern equine encephalitis and West Nile Virus.

There are about 200 different species of mosquitoes in the United States, all of which live in specific habitats, exhibit unique behaviors and bite different types of animals. Despite these differences, all mosquitoes share some common traits, such as a four-stage life cycle. After the female mosquito obtains a blood meal (male mosquitoes do not bite), she lays her eggs directly on the surface of stagnant water, in a depression, or on the edge of a container where rainwater may collect and flood the eggs. The eggs hatch and a mosquito larva, or "wriggler," emerges. The larva lives in the water, feeds and develops into the third stage of the life cycle, called a pupa, or "tumbler." The pupa also lives in the water, but no longer feeds. Finally, the mosquito emerges from the pupal case and the water as a fully developed adult, ready to bite.

The type of standing water in which the mosquito chooses to lay her eggs depends upon the species. The presence of beneficial predators such as fish and dragonfly nymphs in permanent ponds, lakes and streams usually keep these bodies of water relatively free of mosquito larvae. However, portions of marshes, swamps, clogged ditches and temporary pools and puddles are all prolific mosquito breeding sites. Other sites in which some species lay their eggs include tree holes and containers such as old tires, buckets, toys, potted plant trays and saucers and plastic covers or tarpaulins. Some of the most annoying and potentially dangerous mosquito species, such as the Asian tiger mosquito, come from these sites.

Mosquito Life Cycle

The mosquito goes through four distinct stages during its life cycle:

Egg: hatches when exposed to water;
Larva: (plural—larvae) "wriggler" lives in the water; molts several times; most species surface to breathe air;
Pupa: (plural—pupae) "tumbler" does not feed; stage just prior to emerging as adult;
Adult: flies short time after emerging and after its body parts have hardened.

The first three stages occur in water, but the adult is an active flying insect that feeds upon the blood of humans and/or animals. The female mosquito lays the eggs directly on water or on moist substrates that may be flooded with water. The egg later hatches into the larva, the elongated aquatic stage most commonly observed as it swims in the water. The larva transforms into the pupa, then internal changes occur and the adult mosquito takes form. After two days to a week in the pupal stage, the adult mosquito emerges onto the water's surface and flies away. Only female mosquitos take blood, which they usually require for their eggs to develop.
Image of the life cycle of a mosquito. Images are shown in a circle with arrows leading from stage to stage. The cycle begins with an adult mosquito in the air. An arrow points to the next stage in the cycle: eggs laid by the mosquito on the surface of the water. An arrow points to the next stage in the cycle: underwater, eggs become larva. An arrow points to the next stage in the cycle: underwater, larva develop into pupa. An arrow points to the next stage in the cycle: the pupa become emerging adults at the surface of the water. An arrow continues the cycle: emerging adult becomes adult mosquito in the air. Arrows indicate the cycle repeats continuously.
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What do the terms "wriggler" and "tumbler" have in common? (1 point)

They are common names for developmental stages.
They refer to female mosquitos.
They are common names for the larval stage.
They refer to mosquito predators.