A Quick Look at Mosquito Biology

Mosquitoes are insects (actually they are a type of fly) with slender bodies, delicate legs, and wings with scales. The mosquito life cycle is an example of what is called "complete metamorphosis". There are four distinct stages in the life of a mosquito. These stages are:

• Egg
• Larva
• Pupa
• Adult

Eggs are laid by the female mosquito. They can be laid singly or in rafts; on the surface of the water, on the sides of containers, or on damp soil. After the eggs hatch the larvae, or wrigglers, swim in the water and feed on small plants or animals. There are four growth phases in the larva's life, called instars. All instars must come to the surface of the water to breathe, with the exception of a few specialized mosquitoes. At the end of the fourth larval instar, the pupa emerges. Pupae do not feed, but they must come to the surface to breathe. After a short time, generally only a day or two, the adult mosquito emerges from the pupa, dries its body in the air, and flies away. Only female mosquitoes bite, and they use the blood to nourish their eggs. Male and female mosquitoes feed on sugars. After mating and taking a blood meal, a female mosquito will lay her eggs and begin the cycle once again.

Mosquito larvae have bodies that are covered with bristles. They have a siphon at the tail end of the body. The siphon permits the larvae to breathe by penetrating the surface of the water and allowing the larvae to breathe air directly from the atmosphere. Oils and monomolecular films prevent the larvae from breathing; they die from suffocation.

Mosquito pupae also have bristles on their bodies. Some of these bristles allow the pupae to float directly below the surface of the water. The pupae breathe by using their respiratory "trumpets" to draw air directly from the atmosphere. Like larvae, pupae can be killed by cutting off their access to the atmosphere with oils or monomolecular films.

Mosquitoes In The Florida Keys

Over 40 species of mosquitoes have been collected in the Florida Keys. However, only a few of these cause the majority of the problems experienced by Keys residents. The most important species are discussed below.

Ochlerotatus taeniorhynchus

Known as the black saltmarsh mosquito, this species is a pest wherever there are salt marshes. In the eastern United States it occurs from south Texas north to New Hampshire. The name refers to the white ring on the proboscis. It is a fierce biter, and will bite day or night. This mosquito can produce enormous broods which can emerge synchronously, and then migrate several miles. The vast majority of mosquito complaints in the Keys are due to this mosquito.

Culex quinquefasciatus

This is the southern house mosquito. It is found throughout the southern half of the United States. Its name refers to five lines that can be seen on the body. It prefers to lay its eggs in small collections of water, and it will utilize water that is polluted with organic material. This mosquito enters houses readily, hence its name, and can be an annoying pest at night, not only with its bite but with its high-pitched buzz. The southern house mosquito can transmit dog heartworm and St. Louis encephalitis.

Aedes aegypti

This is the yellow fever mosquito. It transmits yellow fever and dengue, as well as dog heartworm. In the United States it is found from southern Texas to South Carolina. This mosquito is a container breeder. Small amounts of water are preferred sites for egg laying. Old tires, clogged gutters, pet dishes, and bird baths are just some of the many sites where this mosquito will lay its eggs.