Mosquitoes are sometimes carriers of dangerous diseases. In humans, these diseases include malaria, yellow fever, dengue and encephalitis, and in dogs, it can lead to heartworm. Most of these diseases, with the exception of human encephalitis and canine heartworm, have been fairly well eliminated from the entire United States. However, outbreaks of mosquito-borne encephalitis have periodically occurred in Missouri, and canine heartworm is an endemic problem, with costs to animal owners escalating each year.
Effective Mosquito Control
The most effective mosquito control measures are aimed at reducing larvae populations by eliminating stagnant water sites and applying larvicide to targeted locations. Effective mosquito control measures — including the elimination of unwanted debris like abandoned tires and maintenance efforts to keep road ditches clear and water free — have done much to control mosquito populations. While this effort reduces the potential for disease transmission, there remains the possibility that illness may occur since the mosquitoes are readily found in the state.
Types of Mosquitoes
Mosquitoes are broadly classified into 2 groups:
- Floodwater mosquitoes − Floodwater mosquitoes lay their eggs on damp soil where flooding will occur or, in some cases, above the water line in tree holes, artificial containers or other small bodies of water. When water fills these areas and floods the eggs, they hatch, and, after a week or so in the larval stages, broods of mosquitoes emerge simultaneously. These mosquitoes are mainly of the pest variety and are the first to emerge in the spring months. The eggs are laid in previous seasons and overwinter in that stage. Some of these have only 1 brood per year, and others emerge continuously throughout the season − with a brood being produced with each significant rain. Eggs of these species have been known to remain viable for up to 5 years after they were laid. Many of these mosquitoes are strong flyers and may range up to 10 miles or more in search of a blood meal. They must have a blood meal to lay eggs.
- Permanent water mosquitoes − Permanent water mosquitoes lay their eggs directly on the water surface − either singly or in rafts. Populations of these grow as the season progresses in relation to the availability of breeding habitat, water, favorable weather conditions and food. Overwintering takes place as adults in protected areas of buildings, caves, etc., or in the larval form, depending on the species. Many of the species in this group do not venture far from their breeding sites.
We have approximately 50 species of mosquitoes in Missouri. Among these, the life span ranges from less than a week to several months. Among all mosquitoes, it is only the female which "bites," and she does this when she needs to obtain the blood meal required to lay viable eggs.
How Mosquito Species Multiply
All mosquitoes begin life as eggs. Under proper conditions, the egg hatches in 2 or 3 days into a larva, which is aquatic, but must breathe air. The larval stage lasts from 4 to 10 days, depending on species and air temperature. After the larval stage, it becomes a pupa, and the pupal stage lasts another day or two. After this, a winged adult emerges.
Mosquitoes can breed in very small areas of water, including tin cans, old tires, drain troughs, household trash, rain pools and puddles − anywhere that still water can be expected to last for 10 days or longer. Large and deep bodies of water are usually not good mosquito breeding areas because of the presence of natural predators (fish, tadpoles) and the action of waves. Mosquito larvae cannot survive without still water or protection by emergent vegetation.
For more information on local mosquitoes, please view the following handbook - “A Synopsis of the Mosquitoes of Missouri and Their Importance From a Health Perspective” (PDF).