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Mosquito Biology

Approximately 47 species of mosquitoes exist in St. Tammany Parish. Fortunately all are not medically important or a nuisance. All mosquitoes go through the same developmental stages: egg, larva, pupa, and adult. The time it takes to go from egg to adult depends upon the species and weather conditions. Generally, this period is 5-14 days for all species. The larval and pupal stages occur in water.

The adult life span of the male mosquito is only a few days, while that of the female can be 4-8 weeks. It is the female mosquito that bites and must have blood to develop the eggs. Adult mosquitoes feed on plant nectars for nourishment. Male mosquitoes will usually remain within their breeding area, while the female can travel several miles from its breeding area in search of a blood meal. The two basic categories of mosquitoes are

(1) Floodwater, which deposit eggs on the soil surface and

(2) Permanent Water, which deposit eggs on the water surface.

Mosquitoes breed in a wide variety of habitats. In St. Tammany Parish, these habitats include the generalized areas of:   (1) Marshland, (2) Woodland and Pastures, (3) Roadside Ditches ,(4) Swamps, and (5) Artificial Containers

The southern part of the parish contains approximately 60,000 square miles of marshland. Several nuisance and medically important species breed in these marshes, some of which are capable vectors for West Nile virus, eastern equine encephalitis, and St. Louis encephalitis. The salt marsh mosquito, whose broods can reach extraordinary numbers, commonly breeds in the marshland.

Thousands of acres of woodland mosquito breeding exist in the parish. Floodwater mosquitoes primarily breed in these areas. Eggs are deposited on the soil surface in low-lying wooded areas such as sloughs, depressions, and potholes. When rainfall occurs, the eggs are flooded, then hatch. Several species of woodland floodwater mosquitoes are common in these area. These mosquitoes affect residents that live close to these woodland areas. Most of these mosquitoes are nuisance type species with only two or three implicated as vectors for mosquito borne viral disease.

Roadside ditches, particularly those that have polluted and septic water, are a source of chronic mosquito breeding. Roadside septic ditches produce extremely large numbers of the southern house mosquito, the primary vector for West Nile virus and St Louis encephalitis. The source of the problem for the breeding of these mosquitoes is from the effluent that enters the ditches from residential filter beds and septic tanks. There are approximately 300 miles of roadside septic ditches in St. Tammany Parish. Fresh water ditches occasionally produce mosquitoes; however, small fish and other aquatic mosquito predators provide a natural control in most cases.

Swamps commonly found in areas along the Pearl, Tchefuncte, and Bogue Falaya River Basins are also a source of chronic mosquito breeding. One of the most common mosquitos that breed in swamps is the Anopheles mosquito, commonly referred to as the malaria mosquito. Occasionally, floodwater mosquitoes will also breed in swamps following drought conditions.

Finally, artificial containers commonly found in residential yards, vacant lots and similar locations can be another major source of mosquito breeding. The Asian tiger mosquito, which is a capable vector for West Nile virus, almost exclusively breeds in these sites. It is also a very aggressive biter, and will seek a blood meal throughout the day. This mosquito deposits its eggs on the inside walls of containers such as cans, buckets, tires, etc., just above the water line. When rainfall fills these containers with water, the eggs hatch and mosquito development begins. Residents can play a major role in preventing this type of breeding by eliminating or storing such containers where they cannot collect water.

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